Valentine:
Have you seen one of these little gizmos?
I wonder if they are well built, have reproducible values and so on?
I have a Taylor mercury type psychrometer as well as a spirits filled psychrometer (Novalynx model 225-570-A). I have not seen any significant difference in the readings from either. Here in Arizona conditions are often dry, and the correct wet bulb depression is rather large, sometimes forty degrees Fahrenheit. I have found it a challenge to get correct wet bulb depression. I've tried whirling the instrument fast or slow as well as simply placing it in an area with a slight breeze. Too often I simply cannot get the wet bulb temperature as low as expected.Q: Do you have accurate TEMP and RH data and is that data in an Excel spreadsheet? There is an Excel "Add-In" software module that can calculate accurate Wet Bulb temperature values.
I also own an Assman psychrometer (Novalynx model 225-5230). I really like this instrument. It consistently provides lower wet bulb temperatures than either of the sling type psychrometers, and agrees with my VP2 and other weather data which I trust.
It would seem that something with my method must be the cause of the issues I've had with the sling psychrometers, so I don't want to be too quick to discourage purchasing one. I would however recommend the Assman psychrometer for ease of use and the consistancy of readings.
But I am also considering getting this one when I get some extra money
https://novalynx.com/store/pc/225-566-Battery-Operated-Psychrometer-p646.htm
This is the highest precision unit sold by Extech +/- 2% . http://www.extech.com/display/?id=14699
Place that carries some good stuff including NWS sling and newer Belfort Psychro-Dyne - Model 595 which came after the 566. http://www.belfort-inst.com/Model_595.htm
Link to store
http://www.iisusa.com/Psychrometers/products/50/
This could be a completely new thread, but if issue is SHT31 looks high and you wanted to compare with another instrument I can confirm it does run high.
My findings on the SHT31 are disappointing with humidity. After long term not happy at all. DP temperature run about 3°F high all the time winter summer doesn't matter but the damn thing still won't make 100% humidity on 4 different units all aspirated.
The SHT-15 I also recently put back in service for comparison reads closer to actual psychrometer and nearby ASOS but also won't make 100% humidity.
SHT31 looks high and you wanted to compare with another instrument I can confirm it does run high.Compared to my previous 11 and 15, the 31 is a rock star. I've used two 31's and they're virtually identical, between 1% and 99% this thing is absolute money. When I reach 1%, the dew does get a little cold, but a RAWS down the street does exactly the same thing. I also was W0X0F last winter and it wouldn't pull the 100% trigger, so I get that. I know you've seen some "competitors" PWS's, if you want disappointment, that's where to look. I don't know any sensor that's affordable that can mach the 31, not even close.
My findings on the SHT31 are disappointing with humidity. After long term not happy at all.
SHT31 looks high and you wanted to compare with another instrument I can confirm it does run high.Compared to my previous 11 and 15, the 31 is a rock star. I've used two 31's and they're virtually identical, between 1% and 99% this thing is absolute money. When I reach 1%, the dew does get a little cold, but a RAWS down the street does exactly the same thing. I also was W0X0F last winter and it wouldn't pull the 100% trigger, so I get that. I know you've seen some "competitors" PWS's, if you want disappointment, that's where to look. I don't know any sensor that's affordable that can mach the 31, not even close.
My findings on the SHT31 are disappointing with humidity. After long term not happy at all.
It's anything but a rock star, I'm disappointed. Maybe it works better at extremely low humidity but for me they run high.Two degrees of dew point is nothing. What's that equate to in humidity, maybe 1/2 of a percent at your temp? If the 15 works for you, go for it. Mine went into the trash long ago.
AP DP was 66 as was my psychrometer.
I can only give snapshot of 3 units but all 3 SHT31's - 69° and SHT15-67°.
It's anything but a rock star, I'm disappointed. Maybe it works better at extremely low humidity but for me they run high.Two degrees of dew point is nothing. What's that equate to in humidity, maybe 1/2 of a percent at your temp? If the 15 works for you, go for it. Mine went into the trash long ago.
AP DP was 66 as was my psychrometer.
I can only give snapshot of 3 units but all 3 SHT31's - 69° and SHT15-67°.
Yes, I guess I'm used to my temps. What now?It's anything but a rock star, I'm disappointed. Maybe it works better at extremely low humidity but for me they run high.Two degrees of dew point is nothing. What's that equate to in humidity, maybe 1/2 of a percent at your temp? If the 15 works for you, go for it. Mine went into the trash long ago.
AP DP was 66 as was my psychrometer.
I can only give snapshot of 3 units but all 3 SHT31's - 69° and SHT15-67°.
At 80° ambient it's 4%.
It's more than nothing and way out of specs.
Yes, I guess I'm used to my temps. What now?
:???: If I were to average out my humidity compared to the two ASOS's and one RAWS around me over a decent span (say a week) I'd bet it'd be within 0 to 1% with the 31. I compare at least a dozen times every single day (night and day), and have done so since the local WFO picked up my PWS on their website about six years ago.
Yes, I guess I'm used to my temps. What now?
Running around 6-7% high on humidity
:???: If I were to average out my humidity compared to the two ASOS's and one RAWS around me over a decent span (say a week) I'd bet it'd be within 0 to 1% with the 31. I compare at least a dozen times every single day (night and day), and have done so since the local WFO picked up my PWS on their website about six years ago.
Yes, I guess I'm used to my temps. What now?
Running around 6-7% high on humidity
Me thinks there's more afoot....
Honestly, I think all that would do is make the response time a touch quicker, it'll do nothing for accuracy. However, be sure it'll certainly dirty up the sensor quicker.:???: If I were to average out my humidity compared to the two ASOS's and one RAWS around me over a decent span (say a week) I'd bet it'd be within 0 to 1% with the 31. I compare at least a dozen times every single day (night and day), and have done so since the local WFO picked up my PWS on their website about six years ago.
Yes, I guess I'm used to my temps. What now?
Running around 6-7% high on humidity
Me thinks there's more afoot....
My only guess then (since I have the Davis 24hr FARS and no boost in airflow) that Davis’ bulky filter cap may have a role in this but then again, it may not be the case.
Maybe Randy can take the filter cap off of one of his units and see if it makes any difference.
Honestly, I think all that would do is make the response time a touch quicker, it'll do nothing for accuracy. However, be sure it'll certainly dirty up the sensor quicker.:???: If I were to average out my humidity compared to the two ASOS's and one RAWS around me over a decent span (say a week) I'd bet it'd be within 0 to 1% with the 31. I compare at least a dozen times every single day (night and day), and have done so since the local WFO picked up my PWS on their website about six years ago.
Yes, I guess I'm used to my temps. What now?
Running around 6-7% high on humidity
Me thinks there's more afoot....
My only guess then (since I have the Davis 24hr FARS and no boost in airflow) that Davis’ bulky filter cap may have a role in this but then again, it may not be the case.
Maybe Randy can take the filter cap off of one of his units and see if it makes any difference.
I wish Davis would ditch the Sensirion sensor and use Vaisala.I'll second that. I would be willing to spend some $$$ for reliable humidity.
Do you have a model number?
Auburn U. should look at the Dyacon stations. They have web portal capabilities. https://dyacon.com/Merely food for thought reference your complaints about the SHT31, the Daycon specs out as the same for temp accuracy, and the humidity only 0.2% (1.8% vs 2%) more accurate, but that's only between 10 and 80%. They don't even state what it is outside those parameters. I know that is no satisfaction for you, but just sayin'....
They use a capacitive RH sensor...but, I DO like their RAIN gauge leveling and drain tubes approach:
Auburn U. should look at the Dyacon stations. They have web portal capabilities. https://dyacon.com/Merely food for thought reference your complaints about the SHT31, the Daycon specs out as the same for temp accuracy, and the humidity only 0.2% (1.8% vs 2%) more accurate, but that's only between 10 and 80%. They don't even state what it is outside those parameters. I know that is no satisfaction for you, but just sayin'....
Auburn U. should look at the Dyacon stations. They have web portal capabilities. https://dyacon.com/
One day, this is about as close to professional equipment I can afford. ....http://www.youngusa.com/products/2/29.htmlI love RMY. That being said, the only thing that disappoints me about the SHT31 is that it wouldn't pull the 100% trigger, stayed on 99 forever, but that was my old 31, haven't had the opportunity with the new one. Remember, the only difference between 99 and 100% is 0.4F spread between temp and dew point, that's pretty razor thin. Both 31's certainly have gotten to 1%, and have done so a few times this year, hell even the TUS ASOS and a RAWS station hit 1%, I've never seen that before.
I know it's just a big expensive thermometer but I've always wanted something I know is accurate and will have a good comparison for the Davis SHT series.
Wonder if the probe could be retrofitted inside a Davis FARS? 7.25 ".
Do you have a model number?
The SHT's are all aspirated not the handheld extech I was checking against. Today we did have a stiff breeze when they all matched so maybe you are on to something but 100% without using Cumulus calibrator won't happen. 97% is max on all units even dense fog for 8 hours.
FYI you can slow and make less dewpoint/humidity swings by lowering the fan speed. This unit works but has a very narrow range as they all do. Aspiration speed even slowed is still 2x above solar fan.
I've tried another speed controllers that failed, would shut fan speed all the way off after few hours but found this unit to keep speed steady and never stops fan.
https://www.amazon.com/gp/product/B00BLOSG7I/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
To me, it seems like all SHT sensors act just about the same when it comes to humidity. The SHT 31 may do better on the low end of the scale but in the mid and upper range, it basically acts almost the same. In the mid range, it as a wet bias and on the high end, it has a dry bias. IMO.
It would be awesome if someone on here had the smarts and the capabilities of making a home brew sensor for the VP2 using something else besides Sensirion.
OR... maybe it's a new revision of the sensor and it's more accurate? Might have to perform surgery and swap the two sensors to find out.
Thank you for the suggestion on the variable fan speed controller. I'll consider that.
I went back and looked at data from the wee hours of this morning when winds kicked up (10-15mph) and the DP on the aspirated station smoothed out. I'm still seeing 4-6% discrepancies in humidity between passive and active shields. Active ALWAYS runs higher. So something is up.
OR... maybe it's a new revision of the sensor and it's more accurate? Might have to perform surgery and swap the two sensors to find out.
Interesting thought where did you purchase the sensor :?:
Both were purchased from Ryan at SI about 1 year apart.
I just set up a passive shield with SHT31 using a 24 hr shield core. I've got plenty of spare parts so drilled some ventilation holes on core for added ventilation and extra louver and 2 extra shields on top. So far with stiff wind the passive is doing ok +.2 warmer than AC fan. Dewpoint 2° lower which is a sign maybe.
I'll test a few days may just leave out as is a see how warm it gets on calm days. :idea:
Here is an interesting journal article on humidity measurements if anyone hasn’t seen it....
https://journals.ametsoc.org/doi/full/10.1175/JTECH-D-12-00232.1
[
Here is an interesting excerpt...
“New capacitive sensors perform well but they usually drift to higher values during deployment (except in arid climates); they perform best at lower humidities and need regular adjustment and recalibration...”
That would explain why CW is having different results with the SHT-31 than Randy & I.
It would also explain why there is a “wet bias” with the SHT-31 for those living in higher humidity environments.
It would also explain why there is a “wet bias” with the SHT-31 for those living in higher humidity environments.
Not sure this is conclusive extra airflow knocks the humidity out of calibrationGranted, not conclusive, but if that were the case, I'd probably be having bigger problems than you, right, but I'm not. Three years on the big fan is conclusive to me that it's not degrading the sensor, at least not noticeably. All I can do is state what I see.
Not sure this is conclusive extra airflow knocks the humidity out of calibrationGranted, not conclusive, but if that were the case, I'd probably be having bigger problems than you, right, but I'm not. Three years on the big fan is conclusive to me that it's not degrading the sensor, at least not noticeably. All I can do is state what I see.
Quoting from page 2041 of that DOI article:Not sure this is conclusive extra airflow knocks the humidity out of calibrationGranted, not conclusive, but if that were the case, I'd probably be having bigger problems than you, right, but I'm not. Three years on the big fan is conclusive to me that it's not degrading the sensor, at least not noticeably. All I can do is state what I see.
"For naturally ventilated screens, ... , errors may be larger in calm conditions. Relative humidity natural varibility and errors are somewhat larger during daylight hours than at night."
Oh, completely get that, and I don't even have a web site (well, NWS). Being a perfectionist can be a curse, one that you, I, and more than a few others on here can relate to.It's a big thing for my website to be accurate, I owe it to my visitors who trust in it.Not sure this is conclusive extra airflow knocks the humidity out of calibrationGranted, not conclusive, but if that were the case, I'd probably be having bigger problems than you, right, but I'm not. Three years on the big fan is conclusive to me that it's not degrading the sensor, at least not noticeably. All I can do is state what I see.
What kind of sensors do they use in those electronic hand held devices?
OK, so I swapped out the two SHT31 sensors this evening. After giving about 20 minutes to acclimate, I'm seeing the reverse of what I was seeing previously. Now the newer sensor inside the active shield reads lower dew points (3-4F) than the passive station. I'll monitor it and report back.
do comparisons before I screw it up in FARS shield.Please ....if anything, loses it's virginity..
I use weather display and it has a very good humidity calibration setup. I have finally got over the must have 100% reading or go nuts lol. For the sake of this thread i broke out my wr-25 station from texas weather inst. which is a high dollar set up that was given to me by a friend who worked at a cable vision that went fiber and quit using it, the only thing i had to do was replace the bearings in the wind cup and direction and it works fine. I don't use it because it is wired and you have to use the cables that came with it or the calibrations are way off. I believe it uses analog voltage readings thus the cable can not be messed with. Anyway i was going to compare humidity readings with my two 31's i have up and running but a problem with that is the Davis only senses the humidity about once a minute and the wr-25 is basically real time, reporting every second, so i get almost 60 readings to 1 for the Davis and yes the humidity does go up and down quite a bit in a minute. But just by eye and looking at it my readings are near enough to each other and my dp according to cwop error is 0.0F so it looks like my 31's are doing fine. I sure do like the near real time updates of the wr-25 and it came with the computer interface wps-10 so i can use wd to see the info. I found out along time ago that trying to compare my readings with other stations or metars was a waste of time. I have a metar 10 miles nw of me and one 12 miles se and sometimes they have 20 to 30 percent difference between them. I sometimes wonder about the metar readings, i report one of the metars was showing -40 degrees every time the temp got down in the 30's and they said they would report it to the repair crews and it went all winter without being fixed. I say trust your own gear and no one elses.
When you look at the specs of the really high dollar sensors nearly all of them are speced between 20 to 40 percent up to 90 percent and above 90 percent they go up in error percentage. The 31 specs at 2% or called nominal and above 90% they show it can go up higher on the error scale. I read a study about sling thermos and how they did a study at a military school where they taught how to use them and found a 5 to 10 percent error in the readings, so many things to consider when using one, how many spings good water supply to wet bulb and reading the chart right to get the humidity. Sure is a lot of places to goof up.
Key wording above was the repeated use of "calibration" which is something VERY few CWOP owners do.
Someone here one of the weather techs only occasionally visits warned about year ago the SHT31 chip was losing humidity calibration fast after just a few months of use he retested and it was off substantially enough he posted results.
It was one of the Sensirion stand alone temp/hum gadget with the SHT31 chip.
He was using his own humidity chamber in testing.
It was kcidwx what he posted about the Gadget with SHT31.
One thing that seriously concerned me with these SHT31 evaluation boards was the long term shift in accuracy on the humidity side. I only test a particular type of sensor in minimum groups of three. When a sensor company is wanting to bid on a government contract it's usually pretty easy for me to secure at least three for testing. Although that's not the case with these evaluation boards, it was more for my own curiosity. The issue is approximately 3 weeks after receiving all three of these evaluation boards, I ran a test at 50% RH. All three were reading low by -1.2%, -1.7% and -1.9%. Almost a year later they were reading +0.5% to +0.8%. I'm at a loss to explain why the large shift over time. I'm not quite ready to call it "drift" because that's an insane amount of drift. I was so concerned, I sent my NIST reference instrument back to Washington D.C. to get it certified again after it was just certified 6 months before. It came back having tested just fine. In the hundreds of sensors I've tested over 20+ years, I never seen this much shift before over the course of a year. I was thinking of getting a fourth one and seeing how it compares right out of the box against these three units that have been running for almost a year. Some sensors do require a conditioning period when first used or what I refer to as exercising the sensor. I know that with some sensor manufacturers when they send you a sample for evaluation, sometimes these are not their best spec'ed sensors. Often they are sensors that are usable but don't quite pass QC 100% for some reason. I wonder if that's what these evaluation boards are. I never did ask Sensirion. The only thing I can think of is since these SHT31 sensors don't have a filter over them, they have become contaminated with dust over time.
https://www.wxforum.net/index.php?topic=32439.msg328209#msg328209
It was kcidwx what he posted about the Gadget with SHT31.
One thing that seriously concerned me with these SHT31 evaluation boards was the long term shift in accuracy on the humidity side. I only test a particular type of sensor in minimum groups of three. When a sensor company is wanting to bid on a government contract it's usually pretty easy for me to secure at least three for testing. Although that's not the case with these evaluation boards, it was more for my own curiosity. The issue is approximately 3 weeks after receiving all three of these evaluation boards, I ran a test at 50% RH. All three were reading low by -1.2%, -1.7% and -1.9%. Almost a year later they were reading +0.5% to +0.8%. I'm at a loss to explain why the large shift over time. I'm not quite ready to call it "drift" because that's an insane amount of drift. I was so concerned, I sent my NIST reference instrument back to Washington D.C. to get it certified again after it was just certified 6 months before. It came back having tested just fine. In the hundreds of sensors I've tested over 20+ years, I never seen this much shift before over the course of a year. I was thinking of getting a fourth one and seeing how it compares right out of the box against these three units that have been running for almost a year. Some sensors do require a conditioning period when first used or what I refer to as exercising the sensor. I know that with some sensor manufacturers when they send you a sample for evaluation, sometimes these are not their best spec'ed sensors. Often they are sensors that are usable but don't quite pass QC 100% for some reason. I wonder if that's what these evaluation boards are. I never did ask Sensirion. The only thing I can think of is since these SHT31 sensors don't have a filter over them, they have become contaminated with dust over time.
https://www.wxforum.net/index.php?topic=32439.msg328209#msg328209
Thanks for posting! Reading through that thread tells me that the SHT-31 isn’t as good of a humidity sensor as the Sensirion specs makes them out to be.
I think he needs to send Davis an email or something and talk them into changing their sensor element.
I think he needs to send Davis an email or something and talk them into changing their sensor element.
Don't think he even owns a Davis his stuff was RM Young if memory serves.
I think he needs to send Davis an email or something and talk them into changing their sensor element.
Don't think he even owns a Davis his stuff was RM Young if memory serves.
Darn...I wished I was born rich instead of “good looking.”
It was kcidwx what he posted about the Gadget with SHT31.
One thing that seriously concerned me with these SHT31 evaluation boards was the long term shift in accuracy on the humidity side. I only test a particular type of sensor in minimum groups of three. When a sensor company is wanting to bid on a government contract it's usually pretty easy for me to secure at least three for testing. Although that's not the case with these evaluation boards, it was more for my own curiosity. The issue is approximately 3 weeks after receiving all three of these evaluation boards, I ran a test at 50% RH. All three were reading low by -1.2%, -1.7% and -1.9%. Almost a year later they were reading +0.5% to +0.8%. I'm at a loss to explain why the large shift over time. I'm not quite ready to call it "drift" because that's an insane amount of drift. I was so concerned, I sent my NIST reference instrument back to Washington D.C. to get it certified again after it was just certified 6 months before. It came back having tested just fine. In the hundreds of sensors I've tested over 20+ years, I never seen this much shift before over the course of a year. I was thinking of getting a fourth one and seeing how it compares right out of the box against these three units that have been running for almost a year. Some sensors do require a conditioning period when first used or what I refer to as exercising the sensor. I know that with some sensor manufacturers when they send you a sample for evaluation, sometimes these are not their best spec'ed sensors. Often they are sensors that are usable but don't quite pass QC 100% for some reason. I wonder if that's what these evaluation boards are. I never did ask Sensirion. The only thing I can think of is since these SHT31 sensors don't have a filter over them, they have become contaminated with dust over time.
https://www.wxforum.net/index.php?topic=32439.msg328209#msg328209
I ordered a Kestrel 5000 meter (+/- 2% supposedly) and will be running some tests with it.
Kestrel not only calibrates and certifies every meter they sell, but they promise that if their unit drifts by more than 0.25% per year you can send the unit to them and they will recalibrate it for free within 5 years of purchase. Not sure how most people would determine which instrument is drifting excessively: their kestrel or the sensor they are checking -- but that's another matter.
They also offer a tune-up service for $75. They'll test and calibrate every weather parameter, clean it and install a new wind impeller & battery. Not bad.
I know the military uses these -- they've got a big contract with Kestrel. So do firefighters, athletic orgs, surveyers, shooting clubs and, of course, storm chasers who proudly display them on TV.
I figured it's probably the best you can do under $1000.
I ordered a Kestrel 5000 meter (+/- 2% supposedly) and will be running some tests with it.
Kestrel not only calibrates and certifies every meter they sell, but they promise that if their unit drifts by more than 0.25% per year you can send the unit to them and they will recalibrate it for free within 5 years of purchase. Not sure how most people would determine which instrument is drifting excessively: their kestrel or the sensor they are checking -- but that's another matter.
They also offer a tune-up service for $75. They'll test and calibrate every weather parameter, clean it and install a new wind impeller & battery. Not bad.
I know the military uses these -- they've got a big contract with Kestrel. So do firefighters, athletic orgs, surveyers, shooting clubs and, of course, storm chasers who proudly display them on TV.
I figured it's probably the best you can do under $1000.
Please let us know your results.
I'm thinking the lifespan on these SHT31 sensors for 2% humidity accuracy is between 6 months and 1 year.
There may be a reason Sensirion uses the prefix "SHT".
Proof it's all about age of sensor.My first 31 had almost two years on it, this current one about five months. I didn't notice the first one getting bad, I just replaced it to see if there was a noticeable difference even after two years of service, and I can honestly say, I did not. Not saying there isn't one, just not noticeable to me, and I hawk this stuff like nobody's business.
I'm thinking the lifespan on these SHT31 sensors for 2% humidity accuracy is between 6 months and 1 year.
SHT 31 drifts with age!All sensors drift with age. The question is to what degree (pun intended, or not...) :roll: the 31 does, and does climate/aspiration/rate of aspiration/dust/dirt/pollen/phase of the moon.........
Proof it's all about age of sensor.
Ron sent me a PM with graphs that demonstrates what's been said here already. His new SHT31 is is running 6% lower humidity than 2 year old sensor only 10 feet distance away. I'll let him comment further if he chooses.
I'm thinking the lifespan on these SHT31 sensors for 2% humidity accuracy is between 6 months and 1 year.
Thanks Ron, good job... =D> it helps clarify what we mostly had figured out. Until they do something different with the 31 either update or go with a new version I'll just swap sensors in spring provided they don't jack price up.
For those living in arid climates sub 60 dew points you should be good for several years.
:-"Thanks Ron, good job... =D> it helps clarify what we mostly had figured out. Until they do something different with the 31 either update or go with a new version I'll just swap sensors in spring provided they don't jack price up.
For those living in arid climates sub 60 dew points you should be good for several years.
but something is clearly wrong--unless you live in Arizona!
Here is some information I received from the good folks at the NWS
Hi Justin! Here is the response below about your weather equipment question which we received from our electronics technicians. Hope this helps. 🙂 ----------------------------------------------------------------------- Our Dew Point Sensor is the Vaisala DTS1. This sensor uses a HUMICAP® capacitive thin film polymer sensor to determine RH. The measured capacitance of the DTS1 probe will vary depending on the amount of moisture in the air. The resistance of the PT 100 temperature sensor is used to determine the sensor air temperature. During periods of high humidity, the sensor electronics will turn on the sensor heater element to improve sensor humidity resolution. The algorithm then computes the dew point temperature using the measured sensor temperature and capacitance values.
Our calibration procedures include verifying accuracy every 90 days, there are no adjustments. We also replace the sensor every 18 months as a time change requirement.
We also use a NWS 1088 hygrothermometer to determine ambient air temperature. This sensor uses a fan to draw air in and across the temperature probe, thus the temperature is aspirated. Our calibrations procedures consist of cleaning, adjusting, and verifying accuracy every 90 days. ----------------------------------------------------------------------------
Anyone want to figure out what the shelf live is if never removed from bag?Purely speculation, but with no current/humidity/dust/dirt/fan/big fan/moon phase......forever. ;)
If you think about it, (I) was expecting too much. 1 year on these sensors especially thoses aspirated isn't really that out of normal if NWS routinely changes there's every 18 months or when needed.
Ron, the way I look at it, ya gotta pay to play (performance, performance, performance). Perhaps this is just the price of greater accuracy with this sensor, burn out.If you think about it, (I) was expecting too much. 1 year on these sensors especially thoses aspirated isn't really that out of normal if NWS routinely changes there's every 18 months or when needed.
I don't recall the predecessor to the SHT31 having this issue, but I may be wrong. That said, for a semi-professional station like the VP2, having to replace this sensor every 12-18 months doesn't seem right to me.
Ron, the way I look at it, ya gotta pay to play (performance, performance, performance). Perhaps this is just the price of greater accuracy with this sensor, burn out.If you think about it, (I) was expecting too much. 1 year on these sensors especially thoses aspirated isn't really that out of normal if NWS routinely changes there's every 18 months or when needed.
I don't recall the predecessor to the SHT31 having this issue, but I may be wrong. That said, for a semi-professional station like the VP2, having to replace this sensor every 12-18 months doesn't seem right to me.
My 2 cents.
Ha, easily, blindfolded to boot.Ron, the way I look at it, ya gotta pay to play (performance, performance, performance). Perhaps this is just the price of greater accuracy with this sensor, burn out.If you think about it, (I) was expecting too much. 1 year on these sensors especially thoses aspirated isn't really that out of normal if NWS routinely changes there's every 18 months or when needed.
I don't recall the predecessor to the SHT31 having this issue, but I may be wrong. That said, for a semi-professional station like the VP2, having to replace this sensor every 12-18 months doesn't seem right to me.
My 2 cents.
OR, Davis is testing us to see if we can thread three long screws through the rain base and the rest of the station, remove and install the sensor, and put the station successfully back together again and still love Davis in the morning!
Yeah not interested in removing filter I think it would just cause another issue.
This is sunrise what I'm seeing this morning Extech outside for about 15 minutes, you can see it's dripping with sweat in short period. The SHT15 isn't a solution either for 100% or even close. Remember the SHT's are saturated all night in high humidity and should be reading at least 98%. Airport was 100% at same time.
FYI sent an email to Ryan at Scaled Inst. who I purchased all of mine through expressing concern and verifying they are genuine Davis sensors. If you read data sheet about sensor they have different qualities stamped on each one. Also emailed Davis Inst.
At least they will know now and maybe Davis will investigate on their own.
Dj1225 thanks for chiming in. The topic heading probably should be changed since it turned into SHT31 reliability thread.
I’m thinking about getting a sling psychrometer to make sure that my RH sensor is within specs. I would like to know which psychrometers are accurate and reliable. Thanks!
I’m thinking about getting a sling psychrometer to make sure that my RH sensor is within specs. I would like to know which psychrometers are accurate and reliable. Thanks!
So rather than me reading the 163 posts, have you bought your sling yet? solve your problem?
The question now becomes: how long is the warranty period?
My out-of-spec sensor was purchased April 2017. Does that qualify?
Ryan will take any 31 back if purchased through others it will be a Davis decision but being an known issue my guess all will be covered.
Now that I'll believe when I see it.The question now becomes: how long is the warranty period?
My out-of-spec sensor was purchased April 2017. Does that qualify?
Ryan will take any 31 back if purchased through others it will be a Davis decision but being an known issue my guess all will be covered.
convince Davis to step up and Davis can convince Sensirion to stabilize drift or else risk losing a big contract.
Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
Yes, my comment was geared towards Davis, not Ryan. Honestly, not holding my breath with Davis, I think they'll say we did our R&D, take it or leave it, if they comment at all for that matter.Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
That is the approach I've had from them before but Ryan is different and reliable for sure.
Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
That is the approach I've had from them before but Ryan is different and reliable for sure.
Still nothing back from Davis Inst.
They may or may not get back I've had it both ways and been flat lied to before when I pointed out an software issue for cup size with Vue console using VP2 wind sensor.
They claimed they ran wind tunnel test which I know wasn't true if they had they would of seen problem immediately.
It wasn't just me but multiple people with VP2 and Vue consoles were seeing different wind speeds.
Long story short they did a Vue firmware update, not long after and first one in years (how convenient).
With no mention in update but it fixed issue. I almost didn't bother with it but someone said it fixed the wind speed issue and sure enough it did.
Now both Vue and Vp2 consoles follow each other perfectly.
I'm confused, changing the temp does effect the RH, why would you not want the offset to effect it?Last year I pointed out to them that temperatures could be adjusted in the VP2 console (via offsets) without a corresponding change in relative humidity and they acted like that was news to them (on a 12 year old console).Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
That is the approach I've had from them before but Ryan is different and reliable for sure.
Still nothing back from Davis Inst.
They may or may not get back I've had it both ways and been flat lied to before when I pointed out an software issue for cup size with Vue console using VP2 wind sensor.
They claimed they ran wind tunnel test which I know wasn't true if they had they would of seen problem immediately.
It wasn't just me but multiple people with VP2 and Vue consoles were seeing different wind speeds.
Long story short they did a Vue firmware update, not long after and first one in years (how convenient).
With no mention in update but it fixed issue. I almost didn't bother with it but someone said it fixed the wind speed issue and sure enough it did.
Now both Vue and Vp2 consoles follow each other perfectly.
I'm confused, changing the temp does effect the RH, why would you not want the offset to effect it?Last year I pointed out to them that temperatures could be adjusted in the VP2 console (via offsets) without a corresponding change in relative humidity and they acted like that was news to them (on a 12 year old console).Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
That is the approach I've had from them before but Ryan is different and reliable for sure.
Still nothing back from Davis Inst.
They may or may not get back I've had it both ways and been flat lied to before when I pointed out an software issue for cup size with Vue console using VP2 wind sensor.
They claimed they ran wind tunnel test which I know wasn't true if they had they would of seen problem immediately.
It wasn't just me but multiple people with VP2 and Vue consoles were seeing different wind speeds.
Long story short they did a Vue firmware update, not long after and first one in years (how convenient).
With no mention in update but it fixed issue. I almost didn't bother with it but someone said it fixed the wind speed issue and sure enough it did.
Now both Vue and Vp2 consoles follow each other perfectly.
You gotta be kidding me........ :shock: I didn't even check for such a thing, that's an absolute assumable! Talk about wx 101...:roll:I'm confused, changing the temp does effect the RH, why would you not want the offset to effect it?Last year I pointed out to them that temperatures could be adjusted in the VP2 console (via offsets) without a corresponding change in relative humidity and they acted like that was news to them (on a 12 year old console).Wow, I'm happily shocked about returns. I figured it would be a "pound sand " approach, nature of the beast thing. Nicely done Randy. =D>
That is the approach I've had from them before but Ryan is different and reliable for sure.
Still nothing back from Davis Inst.
They may or may not get back I've had it both ways and been flat lied to before when I pointed out an software issue for cup size with Vue console using VP2 wind sensor.
They claimed they ran wind tunnel test which I know wasn't true if they had they would of seen problem immediately.
It wasn't just me but multiple people with VP2 and Vue consoles were seeing different wind speeds.
Long story short they did a Vue firmware update, not long after and first one in years (how convenient).
With no mention in update but it fixed issue. I almost didn't bother with it but someone said it fixed the wind speed issue and sure enough it did.
Now both Vue and Vp2 consoles follow each other perfectly.
No, that's what I'm saying. Currently, changing the temperature via an offset in the console does NOT affect the RH. That's not correct. I pointed it out and Keystone Cops ensued over at Davis HQ.
Brett Lane head of Davis support as it relates to the VP2, just acknowledged my email to him this morning where I pointed out the “gist” of this thread. Next steps? Who knows.'
Humm.... this just have me an idea. Many of us had to subtract .9 with new SHT31's and older transmitters. I did it using Davis software maybe I need to do it using the Cumulus software and humidity will adjust.
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Heard back from Ryan he doesn't think there is an issue with Davis covering for replacements.
If you purchased through him send defective units back.
As far as solution which I would rather have than keep replacing nothing yet but hopefully it will now get addressed as they say the ball is rolling with appropriate people notified.
Why the 0.9 degree 'correction' in the SIM?
This may not be as open closed as expected for replacements.
So my email has been getting dinged that there's been replies to the SHT-31 thread. :lol: My thoughts on the SHT-31 have already been expressed. I have not read this entire thread but I want to address the topic of humidity sensor replacement. In the professional world, it is standard practice to replace electronic humidity sensors at a minimum of every 24 months. My standard practice has been every 18 months. For the SHT-31, I would recommend in humid environments, every 9-12 months minimum. Dry environments, every 12-15 months. Extreme dry environments every 15-18 months.
I only approve of two ways for checking humidity sensor accuracy. Using a humidity sensor calibration chamber is my #1 choice. My #2 choice is a sling psychrometer out in the field. It's very important to have a matched set of thermometers in the psychrometer. It's also important to have the psychrometer certification tested so you know precisely what the temperature correction is on the dry bulb and wet bulb thermometers. If you break one of the thermometers, you need to replace both with another matched set. Also, you need to use the psychrometer correctly. I'm amazed when I'm at a station and see the tech using the sling incorrectly. I've seen them sling with the sling in direct sunlight, only 6 inches away from their body, using tap water on the wick, etc. :lol:
As far as using another electronic humidity sensor to check another one? I wouldn't.
So my email has been getting dinged that there's been replies to the SHT-31 thread. :lol: My thoughts on the SHT-31 have already been expressed. I have not read this entire thread but I want to address the topic of humidity sensor replacement. In the professional world, it is standard practice to replace electronic humidity sensors at a minimum of every 24 months. My standard practice has been every 18 months. For the SHT-31, I would recommend in humid environments, every 9-12 months minimum. Dry environments, every 12-15 months. Extreme dry environments every 15-18 months.
I only approve of two ways for checking humidity sensor accuracy. Using a humidity sensor calibration chamber is my #1 choice. My #2 choice is a sling psychrometer out in the field. It's very important to have a matched set of thermometers in the psychrometer. It's also important to have the psychrometer certification tested so you know precisely what the temperature correction is on the dry bulb and wet bulb thermometers. If you break one of the thermometers, you need to replace both with another matched set. Also, you need to use the psychrometer correctly. I'm amazed when I'm at a station and see the tech using the sling incorrectly. I've seen them sling with the sling in direct sunlight, only 6 inches away from their body, using tap water on the wick, etc. :lol:
As far as using another electronic humidity sensor to check another one? I wouldn't.
Unfortunately the Sensirion SHT-31 is (currently) the ONLY sensor compatible with our Davis units...unless you WANT to go BACK to the older SHT-11 or SHT-15 sensors.
Because of the communication change inherent with newer sensors, the SHT-31 is an "end-of-the-line" device, the last of its kind until/if DAVIS comes up with a new ISS.
So my email has been getting dinged that there's been replies to the SHT-31 thread. :lol: My thoughts on the SHT-31 have already been expressed. I have not read this entire thread but I want to address the topic of humidity sensor replacement. In the professional world, it is standard practice to replace electronic humidity sensors at a minimum of every 24 months. My standard practice has been every 18 months. For the SHT-31, I would recommend in humid environments, every 9-12 months minimum. Dry environments, every 12-15 months. Extreme dry environments every 15-18 months.
I only approve of two ways for checking humidity sensor accuracy. Using a humidity sensor calibration chamber is my #1 choice. My #2 choice is a sling psychrometer out in the field. It's very important to have a matched set of thermometers in the psychrometer. It's also important to have the psychrometer certification tested so you know precisely what the temperature correction is on the dry bulb and wet bulb thermometers. If you break one of the thermometers, you need to replace both with another matched set. Also, you need to use the psychrometer correctly. I'm amazed when I'm at a station and see the tech using the sling incorrectly. I've seen them sling with the sling in direct sunlight, only 6 inches away from their body, using tap water on the wick, etc. :lol:
As far as using another electronic humidity sensor to check another one? I wouldn't.
Appreciate you comment kcidwx and yes your old review of the SHT31 and thoughts came up as some are realizing how fast they are going high. I'm taking your advice on change out and do highly recommend others do the same being you are the expert on the subject.
Now we have Davis Inst. involved not sure this will go anywhere. They are rather defensive of their products as they should be.
jgentry, I never tested the temperature side of the SHT-31. So, I can't speak to its accuracy. The one thing that bothers me with the way Davis uses the SHT-31 is the aspiration. We don't aspirate humidity sensors. The ASOS DTS1 is not aspirated. You want to keep that sensor clean or it can go out of calibration. So putting the SHT-31 in the FARS and drawing the dirty outside air across it bothers me. I don't know how good the filtration is on that FARS or how easily dust and dirt can get to it by other means.
Please recall earlier in the thread where I quoted from The Weather Observer's Handbook in which Stephen Burt wrote in 2012 that the cheapest capacitive humidity sensors had 5% or more movement per year. Is that what Davis puts in the VP2? The cheapest sensor? I would think such a sensor would be relegated to the <$200 weather stations sold by their competitors. Here we are all these years later and we should just accept that the humidity will be, what, 8-10% off in 2 years? How does that square with the vendor claiming 0.25% drift per year?
Something isn't right here. I'm not saying it's entirely Davis' fault. But the SHT31s have been in production since early 2016 and this is the first anyone's heard of the sensor package being a disposable maintenance item.
Until specs are changed, this is a defective part and should be subject to warranty claims.
I haven't read this whole thread, but regarding contamination, Sensiron recommend that their sensors are placed behind a filter and supply chip enclosures that effectively use a Gortex membrane. Davis chose not to incorporate such a filter.
I find that periodically giving my sht devices a wash in distilled water restores much of their humidity accuracy. I've not seen much drift in the temperature readings.
1.1
Recommended Operating Condition
The sensor shows best performance when operated within recommended normal temperature and humidity range of 5°C–60 °C and 20 %RH–80 %RH, respectively. Long-term exposure to conditions outside normal range, especially at high humidity, may temporarily offset the RH signal (e.g.+3%RH after 60h kept at >80%RH). After returning into the normal temperature and humidity range the sensor will slowly come back to calibration state by itself. Prolonged exposure to extreme conditions may accelerate ageing. To ensure stable operation of the humidity sensor, the conditions described in the document “SHTxx Assembly of SMD Packages”, section “Storage and Handling Instructions” regarding exposure to volatile organic compounds have to be met. Please note as well that this does apply not only to transportation and manufacturing, but also to operation of the SHT3x.
Reconditioning Procedure SHT3x
The following reconditioning procedure may bring the sensor back to calibration state:
Baking: 100 – 105°C at < 5%RH for 10h
Re-Hydration: 20 – 30°C at ~ 75%RH for 12h
5 minute sampled RH for both instruments for a winter and summer month (January 2009 data in red and May 2009 in blue): in all, 17 780 pairs of observations. The thick dashed line marks the trend line that would be expected with a ‘perfect’ agreement; points above the line indicate where the VP2 indicated higher than the Vaisala sensor, and vice versa below the line.
Apparently DAVIS is only cautious about "dust" and not actual water condensing upon the RH sensor and thus physically "wetting" the mylar capacitive sensor.
Using the factory filter is not hard to do, i use them on the 31 and the 15. They are different types with the 31 being smaller than the fl1 which fits the 15. I just cut the little mounting tabs off and hold the filter in place with a little sealing putty i have on hand, takes very little. The small filter gives better response time compared to the large one from Davis. I have used them for years without any problems.
Apparently DAVIS is only cautious about "dust" and not actual water condensing upon the RH sensor and thus physically "wetting" the mylar capacitive sensor.
I seem to recall discussion awhile back about the choice of that cap over the sensor. There's some reason they chose it and decided against the manufacturer's recommended cap. But I can't recall it exactly. Not enough air movement, perhaps.
In any event, they should have known that by choosing that cap design (which lets in just about anything), they were sentencing the sensor to a short life.
Now reconsider their doc where they claim you can go 5 years without the sensor needing "recalibration" (whatever that means; replacement probably). That seems like a bad joke.
Using the factory filter is not hard to do, i use them on the 31 and the 15. They are different types with the 31 being smaller than the fl1 which fits the 15. I just cut the little mounting tabs off and hold the filter in place with a little sealing putty i have on hand, takes very little. The small filter gives better response time compared to the large one from Davis. I have used them for years without any problems.
Using the factory filter is not hard to do, i use them on the 31 and the 15. They are different types with the 31 being smaller than the fl1 which fits the 15. I just cut the little mounting tabs off and hold the filter in place with a little sealing putty i have on hand, takes very little. The small filter gives better response time compared to the large one from Davis. I have used them for years without any problems.
Using the factory filter is not hard to do, i use them on the 31 and the 15. They are different types with the 31 being smaller than the fl1 which fits the 15. I just cut the little mounting tabs off and hold the filter in place with a little sealing putty i have on hand, takes very little. The small filter gives better response time compared to the large one from Davis. I have used them for years without any problems.
I see them on Amazon: https://www.amazon.com/SENSIRION-SF2-FILTER-CAP-SHT2X/dp/B018CQ2USS (https://www.amazon.com/SENSIRION-SF2-FILTER-CAP-SHT2X/dp/B018CQ2USS). But you say there are different sizes. Where do you obtain the filter for the 31?
For those that read my last post, I deleted it, I had the wrong cover. :oops:
Poo... :-) Ya know what? If we go in on a group buy of 10, we can save one cent per filter!! It's our lucky day guys!!! \:D/For those that read my last post, I deleted it, I had the wrong cover. :oops:
Too late :grin: But you brought up a good point even if by mistake. Davis made the decision not to include the polyimide foil dedicated to protect the sensor opening from pollution. Cheaper but may have solved the problem of contamination if it's the problem.
I bought 10 of them because of paying shipping only once and when i change one out i put it up and put a new one on and don't have to clean any until i get them all used. I had one on for a year and it never showed any signs of clogging up.
Davis made the decision not to include the polyimide foil dedicated to protect the sensor opening from pollution. Cheaper but may have solved the problem of contamination if it's the problem.
Nobody's mentioned it, but most probably know it, but there IS a possibility that DAVIS uses the combined TEMP/RH sensor because internally within the ISS they need the TEMP to compensate the RH sensor's temperature non-linearity. Anybody know for sure *IF* the SHT-31 needs temp-compensation?
Nobody's mentioned it, but most probably know it, but there IS a possibility that DAVIS uses the combined TEMP/RH sensor because internally within the ISS they need the TEMP to compensate the RH sensor's temperature non-linearity. Anybody know for sure *IF* the SHT-31 needs temp-compensation?
It was mentioned they are totally different circuits yesterday I believe the big debate with Davis techs why you can change temperature and RH doesn't move.
I was just thinking how all this discussion is about a 45 dollar sensor. When the cost is considered it is a very good deal for home use. I priced the Vaisala HMP155 sensor which is one of the better ones out there and the price was 823.00 dollars, wow. The spec for the top end stopped at 97% and it was + or - 1.8% not far from the cheap 31 spec. at 100%. I am just glad that there is a sensor that works really well at a price i can afford. I can buy a whole lot of replacement sensors for the price of the better sensor lol.
I was just thinking how all this discussion is about a 45 dollar sensor. When the cost is considered it is a very good deal for home use. I priced the Vaisala HMP155 sensor which is one of the better ones out there and the price was 823.00 dollars, wow. The spec for the top end stopped at 97% and it was + or - 1.8% not far from the cheap 31 spec. at 100%. I am just glad that there is a sensor that works really well at a price i can afford. I can buy a whole lot of replacement sensors for the price of the better sensor lol.
Here is link to Mouser the filter is 1.06 plus shipping.https://www.mouser.com/Sensirion/Sensors/Sensor-Hardware-Accessories/_/N-11ei3?P=1ytt2dn It is the sf2 filter.
I was just thinking how all this discussion is about a 45 dollar sensor. When the cost is considered it is a very good deal for home use. I priced the Vaisala HMP155 sensor which is one of the better ones out there and the price was 823.00 dollars, wow. The spec for the top end stopped at 97% and it was + or - 1.8% not far from the cheap 31 spec. at 100%. I am just glad that there is a sensor that works really well at a price i can afford. I can buy a whole lot of replacement sensors for the price of the better sensor lol.
As far as why you shouldn't aspirate a humidity sensor goes.... Two things that will kill a humidity sensor prematurely, contaminants/pollution and condensation.Well, according to Senserion, this filter, when properly sealed around the sensor should eliminate all these factors.
As far as why you shouldn't aspirate a humidity sensor goes.... Two things that will kill a humidity sensor prematurely, contaminants/pollution and condensation.Well, according to Senserion, this filter, when properly sealed around the sensor should eliminate all these factors.
No.As far as why you shouldn't aspirate a humidity sensor goes.... Two things that will kill a humidity sensor prematurely, contaminants/pollution and condensation.Well, according to Senserion, this filter, when properly sealed around the sensor should eliminate all these factors.
So does the Davis 24 hour FARS seal it like this to eliminate “these factors”?
but wanted to be able to remove the filter for cleaning.Why? If the inside is sealed, why would removal be necessary?
Because i had no info as to how well the filter would perform until i tried one and with the seal all the way around the outside of the filter the only way the air can be sampled is through the membrane. When you compare the big Davis shield to the really small fl2 filter and its little opening it looks like it would plug up in no time but even out here in the country surrounded by farm land that is plowed and harvested all the time with crop dusting a surface spraying it has held up real well. My humidity runs over 90% nearly every night unless in a major drought lol. Two of my 3 sensors are over 2 years old in this bad, humid and dusty area and are still tracking with the new sensor i just put in. As far as i can tell i have not had any wet bias.
Food for thot. Old Teleman provided a link several pages ago in this thread to an academic study which concluded that naturally aspirated humidity readings are, in fact, less accurate, on the whole, than fan aspirated readings. Why? Same reason as with temp readings: on low wind days an artificial environment can build up within the shield. I remember reading that elsewhere too.
At this point, I'd have to side with jerryg. Does it make sense to spend hundreds in initial and ongoing expenses and invite untold headaches all in an effort to save a $45 sensor from annual or semi-annual replacement?
The problem with maintaining two sensors, one in passive for humidity and one aspirated for temp, is that there isn't a Davis console (I'm aware of) that can feed temperature and humidity on separate IDs (what some folks call "channels").
What i have decided to try now with my test setup that has the Davis filter on it is to put a sf2 on it with the Davis shield and see what happens to the response time. Sure would make for some really good shielding, the Davis for the big stuff and the sf2 for the fine stuff. Should be interesting if nothing else. The last info i saw on the air flow was 24 cfm daytime and 11 cfm at night. Also read where the shield is designed for low air flow and in air intake is designed to increase the air flow by 2.7 times by narrowing the input.
Also read where the shield is designed for low air flowI think the low figure for the shield (0.1µm particles at 0.05m/s air flow.) is related to the particles getting through the membrane at the stated flow rate *through* the membrane, not the max air flow you can subject it to.
But there is no air flow though (to a good approximation) through the Sensirion filter. The moisture diffuses through it. Airflow past the sensor keeps it at ambient temp, and keeps 'fresh' air ready to diffuse in/out.
I'm testing three of these evaluation boards right now. RH spec: 1.5%
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
I'm testing three of these evaluation boards right now. RH spec: 1.5%Which kit includes the "data logging" chip & coin battery?
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
I'm testing three of these evaluation boards right now. RH spec: 1.5%Which kit includes the "data logging" chip & coin battery?
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
Just reading the spec sheet, Davis would do well to get their transmitter to take I2c and switch over to IDT’s HS 3001. That’s IMO.
I'm testing three of these evaluation boards right now. RH spec: 1.5%
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
Nice! It would be interesting to see how they compare.
Just reading the spec sheet, Davis would do well to get their transmitter to take I2c and switch over to IDT’s HS 3001. That’s IMO.
Just reading the spec sheet, Davis would do well to get their transmitter to take I2c and switch over to IDT’s HS 3001. That’s IMO.
But aren't SHT35 and HS3001 pretty much on a par? Actually SHT35 looks better in the 90-100% region. Where would HS3001 score over SHT35?
Not saying there aren't differences - they're just not too obvious from the specs, other than details like 0.1% difference in nominal tolerance which may well get lost anyway in slightly different interpretation of the specs - eg what is the difference between tolerance and accuracy or nominal vs max - and differences in eg binning. And yes Davis would need to move away from Sensibus to modern I2C if these were to be relevant to use in VP2 units.
To me, that (end-of-life) indicates that Sensirion is moving on to the I2C interface, necessitating a whole new "development kit."
You are correct, the whole SHT-3X line are I2C and/or analog. Don't know what Sensibus is.
2 spares for the future (or breakage).That's why I just picked up five. #-o
I’m curious if Davis used the HS3001 sensor, would their actions have the same effect on the sensor as Sensirion’s?
Sensor mishandling according to the manufacturers handling document is not uncommon. If you inquire they will just say the handling guidelines are overkill. It's like every time I step foot into a weather office and the computer tech has computer memory modules just thrown around on his work bench. If you inquire about why don't you keep the memory in an ESD bag, use an anti-static wrist strap with an anti-static work mat, you will get told, "Been doing it this way for 20 years. Never had a problem." You'll get the same response with sensor handling. Unless they see a high failure rate, it's business as usual. [emphasis mine]
Just for fun, I still have my three SHT-31 eval boards. In the humidity chamber this morning they were reading:Two "points" I see: (1) 48 minutes to stabilize means "diffusion" or extremely SLOW response time; and (2) the OEM filter probably is inhibiting contaminates.
Stability Time: 42 minutes
Ref Humidity: 45.0%
SHT-31-1: 46.31%
SHT-31-2: 46.20%
SHT-31-3: 46.97%
Number 3 went outside for 6 hours in the shade without a filter on it. And now......
Stability Time: 48 minutes
Ref Humidity: 45.0%
SHT-31-1: 47.12%
SHT-31-2: 47.03%
SHT-31-3: 50.02%
Number 3 is not happy. :lol:
So on the Davis sensor PCB's, there's absolutely nothing but the Davis cap and filter?Yes.
Just for fun, I still have my three SHT-31 eval boards. In the humidity chamber this morning they were reading:
Stability Time: 42 minutes
Ref Humidity: 45.0%
SHT-31-1: 46.31%
SHT-31-2: 46.20%
SHT-31-3: 46.97%
Number 3 went outside for 6 hours in the shade without a filter on it. And now......
Stability Time: 48 minutes
Ref Humidity: 45.0%
SHT-31-1: 47.12%
SHT-31-2: 47.03%
SHT-31-3: 50.02%
Number 3 is not happy. :lol:
What is Davis reply so far if any of you has contacted them?
...
They admit nothing..
I know how they roll from experience when I contacted them about firmware issue on Vue console and VP2 anemometer calibration they denied any issue existed even when I made a video.
Then they come out with console update a few months later, first update in years and issue was fixed. Still no acknowledgement...
They admit nothing...And won't here either.
Our best hope is they start packaging and handling humidity sensors correctly, but I wouldn't count on it.
That's when it's a safety issue, the DOT makes them under US law.They admit nothing..Why couldn't Davis recall the sensors and fix or replace them like auto industry does when parts are found defective ??
I know how they roll from experience when I contacted them about firmware issue on Vue console and VP2 anemometer calibration they denied any issue existed even when I made a video.
Then they come out with console update a few months later, first update in years and issue was fixed. Still no acknowledgement...
They admit nothing...And won't here either.
Our best hope is they start packaging and handling humidity sensors correctly, but I wouldn't count on it.
What is Davis reply so far if any of you has contacted them?
...
As stated previously, I contacted the Davis support person (Brett Lane) and alerted him to the discussion in this thread and provided him a link hereto. He acknowledged receipt of my email but nothing more. If I were Davis I would be very careful posting anything in this Forum, rather I would post something on the Davis website, then post in this thread a link to the Davis website. My guess, Davis is talking internally whether or how to address these issues on its website. If I was a betting man, they will not publish anything; rather just consider our comments should they decide to replace the horribly aging VP-2!
Unrelated to the above, I have been reading this Forum for about 5 years and lately contributing, and there has been considerable fluff in many threads. Not this one. I just spent several hours re reading this thread and identified 11 useful takeaways. When I finish my list, I will seek editing review by contributors to this thread then post. Setting the record straight by a very knowledgeable poster, kcidwx, has been most refreshing.
I'm testing three of these evaluation boards right now. RH spec: 1.5%
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
Just reading the spec sheet, Davis would do well to get their transmitter to take I2c and switch over to IDT’s HS 3001. That’s IMO.
But aren't SHT35 and HS3001 pretty much on a par? Actually SHT35 looks better in the 90-100% region. Where would HS3001 score over SHT35?
Not saying there aren't differences - they're just not too obvious from the specs, other than details like 0.1% difference in nominal tolerance which may well get lost anyway in slightly different interpretation of the specs - eg what is the difference between tolerance and accuracy or nominal vs max - and differences in eg binning. And yes Davis would need to move away from Sensibus to modern I2C if these were to be relevant to use in VP2 units.
I'm testing three of these evaluation boards right now. RH spec: 1.5%
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
How did those sensors perform?
We really could use the special coating to protect from contamination.
As mentioned humidity sensors are not designed to be continually aspirated.
Not taking these special precautions will surely end sensor life sooner than later.
And yes handling and storage and not open air is very important. Open air starts the end of live for sensor prematurely who knows how old they are when we get them. 12 months 24? Who knows.
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.
But I do believe that the RW stations have a similar problem in terms of humidity as the Davis except for in the 90 percentile humidities.
Just looking at some of RW’s data on the company’s website, their temperature readings have a warm bias (most likely due to the shield they use).
In response to the ASOS being warmer than the Davis: I think the ASOS stations may have a warm bias. There is a MMTS at the Extension office in my county and they also have the Davis VP2 locates inside the same fence. The Davis (24hr FARS might add) reads sometimes warmer or colder than the MMTS. Typically by 1°
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
Look at it this way, what happens when your passive shield is running 4-5F warmer than ambient? What's that do to your humidity.... #-oBut just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
Having a FARS setup results in better temperature accuracy and not so accurate humidity readings—so pick your poison. Which is more important to you?
Look at it this way, what happens when your passive shield is running 4-5F warmer than ambient? What's that do to your humidity.... #-oBut just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
Having a FARS setup results in better temperature accuracy and not so accurate humidity readings—so pick your poison. Which is more important to you?
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
Having a FARS setup results in better temperature accuracy and not so accurate humidity readings—so pick your poison. Which is more important to you?
But just thinking about it, I bet this is the reason why RainWise hasn’t produced a FARS version of the MK III.Even if that's true, which I highly doubt, I don't care if fans are bad for the humidity portion of the sensor, I'll never quit using one til something comes along that's superior.
The benefits a FARS to me far outweighs the potential negative.
I was thinking about that also. But then I remembered the RM Young dual sensor temp/hum they run in aspirated shields. Maybe we took the fact because ASOS doesn't aspirate humidity it wasn't done.
Just look at sensor on the RMY temperature tracker and shields they offer both passive and aspirated for the dual sensor probe.
RM YOUNG Temperature tracker they suggest the passive shield with the dual sensor. ](*,)
Welp maybe I was thinking wrong.
So my daughter was on my computer reading this thread and saw the complaints about the SHT-31 not going to 100%. It started raining here a little while ago and she wanted me to share that her weather station goes to 100%. She said maybe you guys should buy one like hers. :lol:
Hers is a Weather Monitor II. :lol: She thinks it's pretty neat she's the only one around here that gets to 100% on WU. :lol:
(https://farm2.staticflickr.com/1803/42679352794_6300e920b4_o.png)
(https://farm2.staticflickr.com/1827/42679370914_a7a1a0e393_o.png)
My Vaisala HMT337 a few feet away is showing 99.5%. Typically, hers is running about +3% over my HMT337.
So my daughter was on my computer reading this thread and saw the complaints about the SHT-31 not going to 100%. It started raining here a little while ago and she wanted me to share that her weather station goes to 100%. She said maybe you guys should buy one like hers. :lol:
Hers is a Weather Monitor II. :lol: She thinks it's pretty neat she's the only one around here that gets to 100% on WU. :lol:
(https://farm2.staticflickr.com/1803/42679352794_6300e920b4_o.png)
(https://farm2.staticflickr.com/1827/42679370914_a7a1a0e393_o.png)
My Vaisala HMT337 a few feet away is showing 99.5%. Typically, hers is running about +3% over my HMT337.
So my daughter was on my computer reading this thread and saw the complaints about the SHT-31 not going to 100%. It started raining here a little while ago and she wanted me to share that her weather station goes to 100%. She said maybe you guys should buy one like hers. :lol:
Hers is a Weather Monitor II. :lol: She thinks it's pretty neat she's the only one around here that gets to 100% on WU. :lol:
(https://farm2.staticflickr.com/1803/42679352794_6300e920b4_o.png)
(https://farm2.staticflickr.com/1827/42679370914_a7a1a0e393_o.png)
My Vaisala HMT337 a few feet away is showing 99.5%. Typically, hers is running about +3% over my HMT337.
Hahaha. Tell her that they don’t make em’ like they used too. Shoot, that’s not bad considering how old the WM II is.
Update on sf2 and Davis filter at same time. When i put new sensor in use on my main station i used the sf2 filter, the same has been in use on the old sensor for a year, i removed the sf2 from the old and put the Davis in place of it for comparison with the new sensor. Well the sf2 filter specs say the sensor performance is the same with or without the filter so i put the sf2 back on the old sensor with the Davis filter on also. I can not see any difference in performance of the old sensor readings with both filters in use. It looks like it could give added protection in high dust and humidity areas. I figured the manufacturer says the sf2 does not have any effect on the sensor readings that maybe it would be worth a try even though the bigger filter does add some lag time on the readings. It is hard to measure lag time using the Davis set up because of the high sampling rates of the temp and humidity readings. Since i started using the sf2 i have not had any humidity related problems like i did when using the big Davis filter. I will never run a sensor without the sf2 in place. I am going to let the test sensor run for some time with both filters in place to see if anything shows up down the road.
With the sf2 and getting rid of the high velocity fan and going back to the Davis fan running on ac i have not had that problem anymore.
Before I put eval board #3 outside and ruined it, I did another 100% humidity test in the chamber. Your best bet for hitting 100% is right out of the box on day one because it just goes downhill from there.
Temperatures are very consistent across all three but did go up some over time.
Chamber Conditions
Humidity: 100.0%
Temperature: 83.0°F
(https://farm1.staticflickr.com/918/28537058247_c762c7a500_b.jpg)
Really the readings are in spec, temp is +- .5f and humidity is typically +-2% but can run up higher to 3% or so.
Those specs are from the sht 31 data sheet not from Davis.
Yesterday I hit 99% on my new sensor today max 98%...Tomorrow?
I did just pull it out and double filtered with the Davis filters.
They do make ESD bubble wrap bags but because of what they're typically made out of, it usually violates the sensor handling/packaging requirements.
My 31's came in this.
(https://farm2.staticflickr.com/1808/28545591227_23045eeaf7_b.jpg)
Hitting 100% on the SHT-31 is not really part of the spec. At 100% humidity it's considered in calibration at >96.5%. If you really want to see 100% when it's 100% humidity then you will have to get into the pro level sensors and they start around $400 each.
They do make ESD bubble wrap bags but because of what they're typically made out of, it usually violates the sensor handling/packaging requirements.
My 31's came in this.
Are you talking about the actual sensor from Sensirion, or the temp/hum sensor for the VP2?
Hitting 100% on the SHT-31 is not really part of the spec. At 100% humidity it's considered in calibration at >96.5%. If you really want to see 100% when it's 100% humidity then you will have to get into the pro level sensors and they start around $400 each.
Hmm... That hurts my feelings. Lol
The one I have at my friend’s farm has reported 100% for the second time in a row. This is after he received 2” of rain yesterday. My main station with FARS is currently reporting 97%
I have read this discussion and yet still am wondering what the technology is that the high priced, more-likely-to-read-100%, type of sensors use? I assume we're talking RM Young, Vaisala, Campbell Scientific and perhaps a few others.
Is it an entirely different technology? do they actually measure dew point (doubt it from looking at most of the sensors on-line) and then do a conversion?
I ran across this cheap indoor sensor that i just had to order, it is spec out as an sht31 sensor. The sensor being used is the sht 3x on the picture but says .5 +/- temp and 2% humidity. It would make a nice cheap unit to use for testing purposes. Here is the link https://www.amazon.com/gp/product/B01HDW58GS/ref=od_aui_detailpages00?ie=UTF8&psc=1
Weather Display, for example, has a tweak that says IF the humidity is 95% or greater, display as 100%
I ordered this one since it reads out in tenths. I just need that extra resolution for my satisfaction. :lol: These will be great for monitoring humidity in garage, basement etc.
https://www.amazon.com/gp/product/B000XTJRRA (https://www.amazon.com/gp/product/B000XTJRRA)
SHT 31 drifts with age! I have two VP2 stations both have the SHT31 sensor--one station is about 2 months old and it has a 24 hour fan (CWOP FW3075) and the other station is about 2 years old and has a daytime fan (CWOP CW5020). Right now, in a western suburb of Chicago (where I live), the new station reports 91, humidity of 44 and dewpoint of 66 whereas the older station reports 91, humidity of 50 and dewpoint of 70. The stations are about 10 feet apart on the same fence and the sun is making both fans rumble today! The newer station always gets lower humidity and dewpoint readings as demonstrated by the attached QC graphs from CWOP. I am not a fan (pun intended) of the QC checks on CWOP but this does raise some eyebrows!
I ordered this one since it reads out in tenths. I just need that extra resolution for my satisfaction. :lol: These will be great for monitoring humidity in garage, basement etc.
https://www.amazon.com/gp/product/B000XTJRRA (https://www.amazon.com/gp/product/B000XTJRRA)
X2 :-)
X3 👌
That's fine and dandy if you're just buying the sensor, but then you've got to put it on the PCB. Don't know about you guys, but mounting that tiny, tiny sensor is waaay above my pay grade. And buying 10 from Ryan ready to go, as much as he'd like it, I ain't shelling out that kind of money for a crap shoot.If you want an SHT31 that goes to 100% then you have to play the lottery. Buy a pack of 10 sensors, test and hope you win by getting one sensor that will reach 100%.Hitting 100% on the SHT-31 is not really part of the spec. At 100% humidity it's considered in calibration at >96.5%. If you really want to see 100% when it's 100% humidity then you will have to get into the pro level sensors and they start around $400 each.
Hmm... That hurts my feelings. Lol
The one I have at my friend’s farm has reported 100% for the second time in a row. This is after he received 2” of rain yesterday. My main station with FARS is currently reporting 97%
Well I've decided to pull the ISS and see what I see. The monsoon is in town so I'm not sure when I'll get out to it, I would MUCH prefer cloud cover, possibly tomorrow. At least we can see if the desert hypothesis holds any water with a two year old 31 vs five months.Weather cooperated with overcast skies so I pulled the ISS and did my comparisons, which are at ideal conditions now. Simply put, I found absolutely no noticeable difference between the 31 that has 2 years of service vs the 5 month old one. Temp, dew, humidity were basically exactly the same. Now, one could say they've drifted the exact same amount, perhaps.
Think of me when I'm pulling cacti hypo's outta my legs in the interest of science. :-({|=
Issue isn't linear at all.I get that. I supplied info on what's going on with my conditions now, and regarding issues, baseless or not, that have been brought up with this sensor, simple as that. Not saying there isn't a problem, merely sharing what I observed. My ISS will be accessible til I decide to put it back out to pasture, and I'll continue testing, if nothing else but for myself. If I find something that may be relevant, I'll share.
That's the issue.
Issue isn't linear at all. Everything is hunky dory just a nice typical summer day mid 88 and DP 67° on average with heat index only 91° around here.
It's always near high heat index advisor levels above 100° the issue arises for me.
Once temps get into 90's and dewpoint 70-80.
Example Actual T93°, DP 75, Hum 56% ,Heat Index 103°
SHT31 will show T93°, DP 78, Hum 62% Heat index 109°
That's the issue.
Issue isn't linear at all. Everything is hunky dory just a nice typical summer day mid 88 and DP 67° on average with heat index only 91° around here.
It's always near high heat index advisor levels above 100° the issue arises for me.
Once temps get into 90's and dewpoint 70-80.
Example Actual T93°, DP 75, Hum 56% ,Heat Index 103°
SHT31 will show T93°, DP 78, Hum 62% Heat index 109°
That's the issue.
Yes! That was the issue I was having and like I said in an earlier post the humidity down on the Gulf Coast is unbearable but when you start noticing the heat index becoming outrageous and laughable (close to 120°) when around the area it's between 100°-108° I knew that something wasn't right, then I came across this topic. My new sensor I received Friday showed better results than my 2+ year old sensor, instead of mid 60s-low 70s humidity percentage while in the low to mid 90s it has been showing mid 50s to low 60s percent range. As far as the 100% issue in 2 days it's topped out at 97% which I hadn't seen with the old sensor in almost a year. It's just very frustrating.
I get that. I supplied info on what's going on with my conditions now, and regarding issues, baseless or not, that have been brought up with this sensor, simple as that. Not saying there isn't a problem, merely sharing what I observed. My ISS will be accessible til I decide to put it back out to pasture, and I'll continue testing, if nothing else but for myself. If I find something that may be relevant, I'll share.
Well, considering the monsoon is here..... As I look at this very moment comparing my dews with the "local gang" there's two 64F's and two 66F's. BTW, I'm using the 2 year old sensor at the moment. ;)I get that. I supplied info on what's going on with my conditions now, and regarding issues, baseless or not, that have been brought up with this sensor, simple as that. Not saying there isn't a problem, merely sharing what I observed. My ISS will be accessible til I decide to put it back out to pasture, and I'll continue testing, if nothing else but for myself. If I find something that may be relevant, I'll share.but come summer and high dew points, watchout...
Issue isn't linear at all. Everything is hunky dory just a nice typical summer day mid 88 and DP 67° on average with heat index only 91° around here.
It's always near high heat index advisor levels above 100° the issue arises for me.
Once temps get into 90's and dewpoint 70-80.
Example Actual T93°, DP 75, Hum 56% ,Heat Index 103°
SHT31 will show T93°, DP 78, Hum 62% Heat index 109°
That's the issue.
I noticed the same thing with the Airport that’s 15 milesnorth of me. Think I only seen 1 Airport station ever report 99% humidity.
I noticed the same thing with the Airport that’s 15 milesnorth of me. Think I only seen 1 Airport station ever report 99% humidity.
Even the vaisala. I realize these are 5 minute averages but still, no 98 and 99 very suspect. I went back and downloaded 60 days of KVTN data and nothing.
Well, not to be one to rush things...
I bought a new Sensiron SHT31 sensor from Ryan back in April of 2016. It's been enjoying a dark, cool existence in a closet ever since. :roll:
I'm getting ready to replace the old sensor (and the rain gauge) and have been following this thread. I've seen my heat indexes go out of sight for a while now, just not sure how long it's really been doing that. My records only go back a year and supposedly the latest readings are the highest so maybe(?) this started since last year(?). It seems I don't really remember the super-high heat index numbers (120'ish) until this year.
Anyhow, it will be interesting to see how things compare with the new(er) sensor installed...when I get it installed. #-o
A question here (yeah, I need someone to hold my hand)... What is the "Davis filter cap"???
Thanks!
Hi guys. Don't post here a lot but have been following this thread closely the last day or two since I have been a loyal Davis customer since 1993 when I got a WMII. Still miss that thing sometimes!
I am also a Contract Weather Observer at KCLT so I have a good bit of experience with ASOS. The reason you do not see 98 or 99 percent readings with ASOS is that it directly measures the DP then calculates RH values using ambient temp where Davis directly measures RH then calculates DP. For example if ASOS measures 70/69 it calculates a RH of 97%. IF the DP moves up to 70 then of course the calculated RH is 100%. You've got to take the differences in the method of measurement into account when comparing your readings to airports. As for the sensors reading up to 100% even the expensive ones like the HMP155 can have issues. Back a few years ago our ASOS would rarely hit 100% even in fog with visibilities of 1/4mi. Then they changed the sensor and it hits 100% with relative ease. I used to obsess about getting to 100% too but don't anymore especially when I can adjust the higher readings using Weather Display.
As for the SHT31 is was initially excited about its improved accuracy but quickly learned it suffered from the same amount if not more drift towards a wet bias as its predecessors. I think its more of a moisture problem than a dust problem. I bought several sensors and when I first installed them I would track about 1-2 degrees higher than surrounding ASOS stations two if which are within 5-7 miles of me (KCLT, KAKH). I do have a lot of vegetation around my house so I take that into account when comparing DP readings to other places. I also have a Viasala HM46 probe I do spot checks with. RH values would be generally the same < 3% difference. However I would notice after the first few very humid spells where we would have a day or two of RH values remain 90% or above the sensor would never quite come back to its reading prior to that. Differences in RH between the SHT31 and the Vaisala would be anywhere from 4-8% with the SHT31 higher. I would buy another sensor and the same thing.
Doing a little research I learned this is really a technological problem. Electronics and weather specifically moisture do not mix. Therefore when using electronics to measure moisture there are a lot of problems to overcome to get accurate readings over the long term of say more than two years. The DTS1 ASOS uses to measure DP comes with features to increase sensor longevity. Its heated in high RH environments to protect it from condensation. It also undergoes a high heat cycle I believe once a day to cleanse any chemical vapors that it may encounter. Even so, as has been mentioned prior in this thread the NWS replaces this very expensive sensor every 18 months. I have recently come across a memo that NWS is looking to upgrade a few sensors for ASOS and the dew point sensor is on that list.
Anyway, bottom line is that if you really want to keep accurate readings in humid climates you need to replace these sensors every year to 18months. I actually went back to the sht75 as they are very easy to switch out and actually seem to drift slightly less than the board mounted sensors. I wired in a female connector then mounted it through a slot I cut into the sensor plate in the FARS unit. Now when I change out the sensors I simply pull out the old one and replace it with the new about every 18 months. I still use the Davis filter and replace that every year. Senserion is phasing out the SHT75 however so I think I'm going to use Jerryg's idea and buy a 31 and replace the Davis filter with the SF2 using plumbers putty to see how that works out.
You might consider just doubling the Davis filter to avoid any chemical fumes that can damage sensor. SF2 filters are very small so whatever putty or glue used will surely get into sensor while drying.
Hi guys. Don't post here a lot but have been following this thread closely the last day or two since I have been a loyal Davis customer since 1993 when I got a WMII. Still miss that thing sometimes!
I am also a Contract Weather Observer at KCLT so I have a good bit of experience with ASOS. The reason you do not see 98 or 99 percent readings with ASOS is that it directly measures the DP then calculates RH values using ambient temp where Davis directly measures RH then calculates DP. For example if ASOS measures 70/69 it calculates a RH of 97%. IF the DP moves up to 70 then of course the calculated RH is 100%. You've got to take the differences in the method of measurement into account when comparing your readings to airports. As for the sensors reading up to 100% even the expensive ones like the HMP155 can have issues. Back a few years ago our ASOS would rarely hit 100% even in fog with visibilities of 1/4mi. Then they changed the sensor and it hits 100% with relative ease. I used to obsess about getting to 100% too but don't anymore especially when I can adjust the higher readings using Weather Display.
As for the SHT31 is was initially excited about its improved accuracy but quickly learned it suffered from the same amount if not more drift towards a wet bias as its predecessors. I think its more of a moisture problem than a dust problem. I bought several sensors and when I first installed them I would track about 1-2 degrees higher than surrounding ASOS stations two if which are within 5-7 miles of me (KCLT, KAKH). I do have a lot of vegetation around my house so I take that into account when comparing DP readings to other places. I also have a Viasala HM46 probe I do spot checks with. RH values would be generally the same < 3% difference. However I would notice after the first few very humid spells where we would have a day or two of RH values remain 90% or above the sensor would never quite come back to its reading prior to that. Differences in RH between the SHT31 and the Vaisala would be anywhere from 4-8% with the SHT31 higher. I would buy another sensor and the same thing.
Doing a little research I learned this is really a technological problem. Electronics and weather specifically moisture do not mix. Therefore when using electronics to measure moisture there are a lot of problems to overcome to get accurate readings over the long term of say more than two years. The DTS1 ASOS uses to measure DP comes with features to increase sensor longevity. Its heated in high RH environments to protect it from condensation. It also undergoes a high heat cycle I believe once a day to cleanse any chemical vapors that it may encounter. Even so, as has been mentioned prior in this thread the NWS replaces this very expensive sensor every 18 months. I have recently come across a memo that NWS is looking to upgrade a few sensors for ASOS and the dew point sensor is on that list.
Anyway, bottom line is that if you really want to keep accurate readings in humid climates you need to replace these sensors every year to 18months. I actually went back to the sht75 as they are very easy to switch out and actually seem to drift slightly less than the board mounted sensors. I wired in a female connector then mounted it through a slot I cut into the sensor plate in the FARS unit. Now when I change out the sensors I simply pull out the old one and replace it with the new about every 18 months. I still use the Davis filter and replace that every year. Senserion is phasing out the SHT75 however so I think I'm going to use Jerryg's idea and buy a 31 and replace the Davis filter with the SF2 using plumbers putty to see how that works out.
You might consider just doubling the Davis filter to avoid any chemical fumes that can damage sensor. SF2 filters are very small so whatever putty or glue used will surely get into sensor while drying.
I don't really think doubling up that filter material will keep water off the sensor. That'd be like installing overlapping bug screens with 1-inch holes hoping that will keep the skeeters out. We're talking about tiny coagulates of water vapor that form when the air is near or at saturation.
I will investigate the possibility of mounting it with the clips when my caps arrive by drilling two very small holes in the board. That would be the ideal solution, but probably not possible. If not, then jerryg's solution might be the only one that's been field tested to work.
You shouldn't be getting water on sensor anyway...
You shouldn't be getting water on sensor anyway...
No, I'm not talking about sucking rain into the shield. I'm talking about some combination of very high humidity events that seem to knock the sensor out of spec. That moist air WILL enter the shield either passively or actively. Air nearing saturation becomes like a cloud where tiny water vapor droplets collide, combine and grow in size, even inside the cap. It's got nowhere to go. The SF2 rejects anything over a certain size from getting to the sensor and building up on it. Doubled up, oversized screens aren't going to prevent that situation.
I think its more of a moisture problem than a dust problem.Concur.
If that were the case my strongly aspirated ISS and dirty two year old 31 would not have hit and stayed at both 99% and 1%. I'm sure the filter is there to help protect from dirt/dust, but it's becoming much more evident moisture is the culprit in sensor degradation, not aspiration. As a matter of fact, I'm using the two year old 31 now and it's just as good as the newer one.Well, not to be one to rush things...
I bought a new Sensiron SHT31 sensor from Ryan back in April of 2016. It's been enjoying a dark, cool existence in a closet ever since. :roll:
I'm getting ready to replace the old sensor (and the rain gauge) and have been following this thread. I've seen my heat indexes go out of sight for a while now, just not sure how long it's really been doing that. My records only go back a year and supposedly the latest readings are the highest so maybe(?) this started since last year(?). It seems I don't really remember the super-high heat index numbers (120'ish) until this year.
Anyhow, it will be interesting to see how things compare with the new(er) sensor installed...when I get it installed. #-o
A question here (yeah, I need someone to hold my hand)... What is the "Davis filter cap"???
Thanks!
It's the stock filter Davis uses. The thinking is because of aspiration the sensor gets dirty and makes sensor less accurate.
If that were the case my strongly aspirated ISS and dirty two year old 31 would not have hit and stayed at both 99% and 1%. I'm sure the filter is there to help protect from dirt/dust, but it's becoming much more evident moisture is the culprit in sensor degradation, not aspiration. As a matter of fact, I'm using the two year old 31 now and it's just as good as the newer one.Well, not to be one to rush things...
I bought a new Sensiron SHT31 sensor from Ryan back in April of 2016. It's been enjoying a dark, cool existence in a closet ever since. :roll:
I'm getting ready to replace the old sensor (and the rain gauge) and have been following this thread. I've seen my heat indexes go out of sight for a while now, just not sure how long it's really been doing that. My records only go back a year and supposedly the latest readings are the highest so maybe(?) this started since last year(?). It seems I don't really remember the super-high heat index numbers (120'ish) until this year.
Anyhow, it will be interesting to see how things compare with the new(er) sensor installed...when I get it installed. #-o
A question here (yeah, I need someone to hold my hand)... What is the "Davis filter cap"???
Thanks!
It's the stock filter Davis uses. The thinking is because of aspiration the sensor gets dirty and makes sensor less accurate.
Daughters WMII pegged out all night long at 100% humidity in the fog. I really like this weather station. Too bad you can't get parts for it. I'd really like to know what brand the humidity sensor is. It tracks pretty well with my Vaisala HMT337. Either that or she just got lucky with this one.
Do you know what sensors the NWS will upgrade too?
Humidity sensor aspiration has been shown to accelerate sensor aging. Is this guaranteed to happen 100% of the time? No! However, you have to consider it when troubleshooting your issue. If you have eliminated aspiration as the cause of your sensor problem, then move on to the next thing.Not doubting this. However, considering my ISS setup and climate and apparently still good 2 year old sensor, the fan and dirt ain't the problem (at least for me), being in a wet climate is. That being said, I think it more likely a fan in a wet climate would exacerbate the aging process.
I think you are probably dealing with a moisture problem unrelated to aspiration. As Sensirion even states in their documentation, the sensor will show a wet bias after a high humidity event. However, they also say the sensor should slowly recover from it over time. I don't think the recovery is happening as it should.
Mine just came in the mail. Now the fun part..... #-oYou shouldn't be getting water on sensor anyway...The SF2 rejects anything over a certain size from getting to the sensor and building up on it.
Victoria Emergency Operations Center 91/72
Victoria Regional 91/70 at 4:15p
Victoria (jerryg) 91/76
Ok lets put this in locations, the station at at the 911 center is on the roof of a brick building surrounded by a parking lot and road, the metar at the air port is located off a runway and they put gravel around the site so as not to get stuck, heck with the good readings and mine is located over grass and ground that just got through with 15 inches of rain in the last 4 weeks.
Humidity sensor aspiration has been shown to accelerate sensor aging. Is this guaranteed to happen 100% of the time? No! However, you have to consider it when troubleshooting your issue. If you have eliminated aspiration as the cause of your sensor problem, then move on to the next thing.Not doubting this. However, considering my ISS setup and climate and apparently still good 2 year old sensor, the fan and dirt ain't the problem (at least for me), being in a wet climate is. That being said, I think it more likely a fan in a wet climate would exacerbate the aging process.
I think you are probably dealing with a moisture problem unrelated to aspiration. As Sensirion even states in their documentation, the sensor will show a wet bias after a high humidity event. However, they also say the sensor should slowly recover from it over time. I don't think the recovery is happening as it should.
Mine just came in the mail. Now the fun part..... #-oYou shouldn't be getting water on sensor anyway...The SF2 rejects anything over a certain size from getting to the sensor and building up on it.
It sure would be nice if we had a picture of every location reporting weather info so we could weed out the really poor sited stations and cheap stations that are never even close to the correct readings. It is not just the amateur weather stations but a lot of the "official" stations are poorly sited and maintained also. How can a asos station put gravel around all the gear? My goodness don't they follow their own instructions lol.
I bought five, just in case..... #-oMine just came in the mail. Now the fun part..... #-oYou shouldn't be getting water on sensor anyway...The SF2 rejects anything over a certain size from getting to the sensor and building up on it.
Let us know how the “fun” was so we can determine whether to join you in SF2 land. Where did you order them from and how much are they?
It sure would be nice if we had a picture of every location reporting weather info so we could weed out the really poor sited stations and cheap stations that are never even close to the correct readings. It is not just the amateur weather stations but a lot of the "official" stations are poorly sited and maintained also. How can a asos station put gravel around all the gear? My goodness don't they follow their own instructions lol.
I think they did that because it would help the DP sensor to report actual DP instead of the DP influenced by transpiration from the grass.
Which explains why I come back with battle scars every time I go fetch the ISS. All in the name of science. :grin:It sure would be nice if we had a picture of every location reporting weather info so we could weed out the really poor sited stations and cheap stations that are never even close to the correct readings. It is not just the amateur weather stations but a lot of the "official" stations are poorly sited and maintained also. How can a asos station put gravel around all the gear? My goodness don't they follow their own instructions lol.
I think they did that because it would help the DP sensor to report actual DP instead of the DP influenced by transpiration from the grass.
(which would be desert in Tucson, for example).
It sure would be nice if we had a picture of every location reporting weather info so we could weed out the really poor sited stations and cheap stations that are never even close to the correct readings. It is not just the amateur weather stations but a lot of the "official" stations are poorly sited and maintained also. How can a asos station put gravel around all the gear? My goodness don't they follow their own instructions lol.
That web site's well sited Stevenson screen is over gravel.....It sure would be nice if we had a picture of every location reporting weather info so we could weed out the really poor sited stations and cheap stations that are never even close to the correct readings. It is not just the amateur weather stations but a lot of the "official" stations are poorly sited and maintained also. How can a asos station put gravel around all the gear? My goodness don't they follow their own instructions lol.
This has been done, at least to some degree, and the report filed at http://surfacestations.org/ (http://surfacestations.org/). If you examine their findings you'll realize that only a minority of official stations don't have significant siting issues. If you haven't visited that website before, buckle up.
That web site's well sited Stevenson screen is over gravel.....
No sir, bottom left, two pics, one good siting (according to them), one bad. Frankly, the gravel is white and I'd think of minimal effect.That web site's well sited Stevenson screen is over gravel.....Maybe you're referring to one of the pictures (upper right of home page, for instance) showing examples of what NOT to do when siting a weather station?
No sir, bottom left, two pics, one good siting (according to them), one bad. Frankly, the gravel is white and I'd think of minimal effect.
wu id is KTXVICTO6
Aight gang, I’m going to try something on both of my stations. One being a passive shield with a month old SHT 31 and another one with a year old SHT-31 inside of a 24hr FARS. Both stations are around 6miles apart from each other.With that distance, you'll need to study obs for quite a while to get a "feel" for what and how you're comparing, probably days at least.
If that were the case my strongly aspirated ISS and dirty two year old 31 would not have hit and stayed at both 99% and 1%. I'm sure the filter is there to help protect from dirt/dust, but it's becoming much more evident moisture is the culprit in sensor degradation, not aspiration. As a matter of fact, I'm using the two year old 31 now and it's just as good as the newer one.
420 opinions so far, One question? Have you determined the reliability of the humidity sensor and have you the psychometer in possession for that?
420 opinions so far, One question? Have you determined the reliability of the humidity sensor and have you the psychometer in possession for that?
A drive by question deserves a drive by answer. The humidity sensor is unreliable and there are only a few decent psychrometers. If you want to know more than that you're going to have to EXPEND EFFORT like the rest of us did.
I would assume then, if one sensor is fer-cocked, then the whole unit might be similar. I'd then send the whole dang thing back and buy something more professional and accurate.
However... I must have been blessed, born under a happy cloud, lived right, prayed harder , danced the Wautse better than anyone else in my prime, because my VP2 is spot on. I check it often and it is spot on.
Yup, I'd save my pennies and buy something around the quality of a WeatherHawk 620 Wireless Weather Station. Now for the price, I'd assume it has to be accurate.
I did. I suggested a sling psychrometer. Inexpensive and works fine .I would assume then, if one sensor is fer-cocked, then the whole unit might be similar. I'd then send the whole dang thing back and buy something more professional and accurate.
However... I must have been blessed, born under a happy cloud, lived right, prayed harder , danced the Wautse better than anyone else in my prime, because my VP2 is spot on. I check it often and it is spot on.
Yup, I'd save my pennies and buy something around the quality of a WeatherHawk 620 Wireless Weather Station. Now for the price, I'd assume it has to be accurate.
If only we could trade your assumptions for something valuable!
No, people CAN'T just send it back for a refund. That's not how it works anywhere except for a short period after purchase.
And, no, just because something is expensive doesn't make it better. Spec sheets don't always reflect reality as this thread demonstrates.
Got any more cheap wise cracks, or are you ready to contribute to the thread? Perhaps start by telling us how you verify your VP2 is accurate. Maybe you have a psychrometer or hygrometer you trust? And, if so, how do you know that device is accurate?
I did. I suggested a sling psychrometer. Inexpensive and works fine .
...
Yes, I suggested that early on.
I am done offering any suggestion.
This was back on 2/16, we were WOXOF (super rare here), I hit 99% starting at 10pm and stayed there til, wait for it.......
If that were the case my strongly aspirated ISS and dirty two year old 31 would not have hit and stayed at both 99% and 1%. I'm sure the filter is there to help protect from dirt/dust, but it's becoming much more evident moisture is the culprit in sensor degradation, not aspiration. As a matter of fact, I'm using the two year old 31 now and it's just as good as the newer one.
I'm having a hard time finding 99% when did this occur? Last 30 days which includes the humid season monson highest is low 90's.
I just ordered a nist sensor so i will have a calibrated reference to check my working sensor. Ryan over at Scaled Inst. now has the sensor with calibration pricing on his site.Ryan has good things at a reasonable price.
I'm testing three of these evaluation boards right now. RH spec: 1.5%
https://www.idt.com/products/sensor-products/humidity-sensors (https://www.idt.com/products/sensor-products/humidity-sensors)
I'll run them against my three SHT-31 evaluation boards as well.
Ok just to put some info out there for those who want some accuracy in their sensor i asked Ryan over at Scaled Inst. about a calibrated sensor and he got word back from Davis they offer an nist traceable with paperwork for 100 dollars plus the price of a sensor. That would be the best way to have a known reference to work with.
I’m getting the feeling that it doesn’t matter if you have the SF2 filter or not, the SHT-31 is going to have a wet bias during the daytime hours.
The only other idea I have is to calibrate the humidity on the console. That will work fairly well until the humidities get closer to 100% (late 80s & 90s).
After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).
So basically I have 2 new sensors both now reach 98%.. Whoopie! I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.
After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).
So basically I have 2 new sensors both now reach 98%.. Whoopie! I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.
I guess a key question is the temp at which Sensirion tests the sensors' humidity spectrum. My guess would be 25C (77F) since I see mention of it along with 63% in the notes on their datasheet. If they aren't testing beyond that, then, indeed, there could be discrepancies elsewhere.
After 4 days with 2 new sensors, my conclusion they aren't much better than the old still running high on DP at those critical levels when its important to be most accurate (high heat index).
So basically I have 2 new sensors both now reach 98%.. Whoopie! I'm beginning to think these sensors are just off. They surely don't come close to meeting the claimed specs when it counts.
I guess a key question is the temp at which Sensirion tests the sensors' humidity spectrum. My guess would be 25C (77F) since I see mention of it along with 63% in the notes on their datasheet. If they aren't testing beyond that, then, indeed, there could be discrepancies elsewhere.
I guess we should’ve paid attention to the “maximum accuracy” on Sensirion’s spec sheet. Lol
They surely don't come close to meeting the claimed specs when it counts.
perhaps bringing in the station to test it in a controlled environment to determine the difference between the sensor and the standard.
How much of a difference if the sensor is removed from the chamber and tested vs. one of the current 3 prime locations in the chamber.
Would you please leave me alone. Why do you seem to think you are in charge here. I have reported you to the moderators and definitely they need to step in and quell your hatred toward me and anything I ask . Just leave me alone. Stop harassing me.perhaps bringing in the station to test it in a controlled environment to determine the difference between the sensor and the standard.
How much of a difference if the sensor is removed from the chamber and tested vs. one of the current 3 prime locations in the chamber.
This is why I bark at you for parachuting into the thread and not bothering to do the least bit of reading. If you had read page 14, for instance, you'd see that Ron had run extensive tests in his humidity chamber and reproduced the wet bias. Then again, Ron's results from his laboratory-grade instrument are just another of 420 "opinions" right?
Look, lots of people have given freely of their time, expertise and money to try to understand and solve a problem that's not their fault. Some of us have thousands invested in a company that, apparently, thinks it can bait and switch us with impunity.
Given the circumstances, it's not a straight line to the answer. We don't have the same testing facilities as the manufacturer. We have to do our best with what we have. The situation, unfortunately, is still evolving on a trial and error basis.
Look, lots of people have given freely of their time, expertise and money to try to understand and solve a problem that's not their fault. Some of us have thousands invested in a company that, apparently, thinks it can bait and switch us with impunity.
Given the circumstances, it's not a straight line to the answer. We don't have the same testing facilities as the manufacturer. We have to do our best with what we have. The situation, unfortunately, is still evolving on a trial and error basis.
Yep can't even calculate the time and money I've put in and continue to put in to try to figure it out. Seems like until Davis ditches this Digital Sbus protocol for the I2C they have us by the you know what. Unless someone here wants to try to build there own ISS transmitter that has a I2C microcontroller I don't see a whole lot of other options other than switching these sensors out every year or so.
Would love to try these sensors out as they look promising but alas, wrong protocol.
https://www.ist-ag.com/en-us/products/hyt-221-calibrated-and-temperature-compensated
Look, lots of people have given freely of their time, expertise and money to try to understand and solve a problem that's not their fault. Some of us have thousands invested in a company that, apparently, thinks it can bait and switch us with impunity.
Given the circumstances, it's not a straight line to the answer. We don't have the same testing facilities as the manufacturer. We have to do our best with what we have. The situation, unfortunately, is still evolving on a trial and error basis.
Yep can't even calculate the time and money I've put in and continue to put in to try to figure it out. Seems like until Davis ditches this Digital Sbus protocol for the I2C they have us by the you know what. Unless someone here wants to try to build there own ISS transmitter that has a I2C microcontroller I don't see a whole lot of other options other than switching these sensors out every year or so.
Would love to try these sensors out as they look promising but alas, wrong protocol.
https://www.ist-ag.com/en-us/products/hyt-221-calibrated-and-temperature-compensated
Looks like this one might work best in high humidity environments.
Here is the data sheet- https://www.ist-ag.com/sites/default/files/DHHYT221_E.pdf
Application notes- https://www.ist-ag.com/sites/default/files/AHHYTM_E.pdf
Look, lots of people have given freely of their time, expertise and money to try to understand and solve a problem that's not their fault. Some of us have thousands invested in a company that, apparently, thinks it can bait and switch us with impunity.
Given the circumstances, it's not a straight line to the answer. We don't have the same testing facilities as the manufacturer. We have to do our best with what we have. The situation, unfortunately, is still evolving on a trial and error basis.
Yep can't even calculate the time and money I've put in and continue to put in to try to figure it out. Seems like until Davis ditches this Digital Sbus protocol for the I2C they have us by the you know what. Unless someone here wants to try to build there own ISS transmitter that has a I2C microcontroller I don't see a whole lot of other options other than switching these sensors out every year or so.
Would love to try these sensors out as they look promising but alas, wrong protocol.
https://www.ist-ag.com/en-us/products/hyt-221-calibrated-and-temperature-compensated
Looks like this one might work best in high humidity environments.
Here is the data sheet- https://www.ist-ag.com/sites/default/files/DHHYT221_E.pdf
Application notes- https://www.ist-ag.com/sites/default/files/AHHYTM_E.pdf
Actually mentions one of the typical applications for the HYT221 for measuring humidity in saunas lol! Wonder how it recovers afterwards though?
FWIW the published literature shows most capacitive sensors go WET above about 90ºF DP...so, asking for "exactness" might be futile...for now.And when is the last time you saw a dew point AOA 90F? :shock: I know I sure as hell wouldn't live there.
Ok new info on the nist calibration check on the 31, that previous info was old stuff and Ryan got an email from Davis and the new info is a 3 point check of +/- 1% at 33% and 80% and +/-2% at 90%. Looks a little better but i think they should have included one around 97%. When you look at a lot of the sensors most of the really good readings are confined to 30 to 90%, not many give much in the way of a good shot of accuracy about 90%.
Ahhh, that sounds better! I guess I should feel fortunate that I have a sensor that'll hit 1% as well as 99.Ooops, (typo) that should've been 90%RH! :oops:FWIW the published literature shows most capacitive sensors go WET above about 90ºF DP...so, asking for "exactness" might be futile...for now.And when is the last time you saw a dew point AOB 90F? :shock: I know I sure as hell wouldn't live there.
FWIW the published literature shows most capacitive sensors go WET above about 90ºF DP...so, asking for "exactness" might be futile...for now.And when is the last time you saw a dew point AOB 90F? :shock: I know I sure as hell wouldn't live there.
No doubt! I have no idea how those people deal with that stuff all-summer-long.FWIW the published literature shows most capacitive sensors go WET above about 90ºF DP...so, asking for "exactness" might be futile...for now.And when is the last time you saw a dew point AOB 90F? :shock: I know I sure as hell wouldn't live there.
You mean Houston :shock:
Got 2 new SHT31's in handled by a different company lets see if they do any better. I just happen to have passive shield I may try. Getting data could be an issue however they do record high and lows however.Randy if I were you, I'd just look for some shade, or make your own.
Good point was brought up why rainwise sensors seem better using the SHT15 on mid to high dp temps in 60-80 range.
Something was brought to my attention by someone not on this thread the molding process Davis uses to mount sensor could be contamination source dooming sensor from getgo. Maybe that's why the reckless handling.
The sensor looks embedded in rubber or plastic which would be against all handling procedures.
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Got 2 new SHT31's in handled by a different company lets see if they do any better. I just happen to have passive shield I may try. Getting data could be an issue however they do record high and lows however.Randy if I were you, I'd just look for some shade, or make your own.
Good point was brought up why rainwise sensors seem better using the SHT15 on mid to high dp temps in 60-80 range.
Something was brought to my attention by someone not on this thread the molding process Davis uses to mount sensor could be contamination source dooming sensor from getgo. Maybe that's why the reckless handling.
The sensor looks embedded in rubber or plastic which would be against all handling procedures.
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Got 2 new SHT31's in handled by a different company lets see if they do any better. I just happen to have passive shield I may try. Getting data could be an issue however they do record high and lows however.
Good point was brought up why rainwise sensors seem better using the SHT15 on mid to high dp temps in 60-80 range.
Something was brought to my attention by someone not on this thread the molding process Davis uses to mount sensor could be contamination source dooming sensor from getgo. Maybe that's why the reckless handling.
The sensor looks embedded in rubber or plastic which would be against all handling procedures.
[ You are not allowed to view attachments ]
Doubtful.Got 2 new SHT31's in handled by a different company lets see if they do any better. I just happen to have passive shield I may try. Getting data could be an issue however they do record high and lows however.
Good point was brought up why rainwise sensors seem better using the SHT15 on mid to high dp temps in 60-80 range.
Something was brought to my attention by someone not on this thread the molding process Davis uses to mount sensor could be contamination source dooming sensor from getgo. Maybe that's why the reckless handling.
The sensor looks embedded in rubber or plastic which would be against all handling procedures.
[ You are not allowed to view attachments ]
Or perhaps RW manipulates the raw readings with software??
Rainwise sensors ain't gonna be cheap. Look at these "Government" (GSA) prices!!!At least the feds got a 29.25% discount. What's there to whine about? :roll:
https://www.gsaadvantage.gov/ref_text/GS07F5342R/GS07F5342R_online.htm (https://www.gsaadvantage.gov/ref_text/GS07F5342R/GS07F5342R_online.htm)
Even with the discount, the prices are ludicrous.We ain't the Feds (nor the Federale's either). :roll:Rainwise sensors ain't gonna be cheap. Look at these "Government" (GSA) prices!!!At least the feds got a 29.25% discount. What's there to whine about? :roll:
https://www.gsaadvantage.gov/ref_text/GS07F5342R/GS07F5342R_online.htm (https://www.gsaadvantage.gov/ref_text/GS07F5342R/GS07F5342R_online.htm)
This morning with humidity up the new acurite with sht31's both peaked at 95% same as the new Davis aspirated. The 2 year old Davis peaked at 93% while the handheld Extech 96% this morning just to complete how these sensors compare.
They do appear to run substantially lower 8% daytime and much closer with airport ASOS yesterday afternoon and evening, along with reaching the upper end of humidity scale 95%, airport also was 94% today. This makes everything really frustrating knowing the 31's can perform just as data sheet says but the Davis Units don't.
Why the Davis sensors run so high I can only conjecture molding into board process contamination.
This is very aggravating after seeing the Acurite $15 sensor work so much better. This probably goes to why the rainwise sensors are much closer and don't seem to suffer like the Davis sensors. They don't destroy sensor before consumer gets them.
I'll let you guys continue but I've seen enough to know the Davis units are junk.
This morning with humidity up the new acurite with sht31's both peaked at 95% same as the new Davis aspirated. The 2 year old Davis peaked at 93% while the handheld Extech 96% this morning just to complete how these sensors compare.
They do appear to run substantially lower 8% daytime and much closer with airport ASOS yesterday afternoon and evening, along with reaching the upper end of humidity scale 95%, airport also was 94% today. This makes everything really frustrating knowing the 31's can perform just as data sheet says but the Davis Units don't.
Why the Davis sensors run so high I can only conjecture molding into board process contamination.
This is very aggravating after seeing the Acurite $15 sensor work so much better. This probably goes to why the rainwise sensors are much closer and don't seem to suffer like the Davis sensors. They don't destroy sensor before consumer gets them.
I'll let you guys continue but I've seen enough to know the Davis units are junk.
Randy would you consider switching back to the SHT15?
This morning with humidity up the new acurite with sht31's both peaked at 95% same as the new Davis aspirated. The 2 year old Davis peaked at 93% while the handheld Extech 96% this morning just to complete how these sensors compare.Try a 75...tiny thermal mass, preinstalled to a board by Sensirion, and plug and play after a little soldering or 1.27mm 4-pin connector.
They do appear to run substantially lower 8% daytime and much closer with airport ASOS yesterday afternoon and evening, along with reaching the upper end of humidity scale 95%, airport also was 94% today. This makes everything really frustrating knowing the 31's can perform just as data sheet says but the Davis Units don't.
Why the Davis sensors run so high I can only conjecture molding into board process contamination.
This is very aggravating after seeing the Acurite $15 sensor work so much better. This probably goes to why the rainwise sensors are much closer and don't seem to suffer like the Davis sensors. They don't destroy sensor before consumer gets them.
I'll let you guys continue but I've seen enough to know the Davis units are junk.
I just logged in yesterday for the first time in awhile so maybe you've addressed this, but have you tried a NIST certified sensor?
I'm pretty sure in his recent posts he was doing experiments with 2 newer acurite sensors and a 5 day old SHT31.I just logged in yesterday for the first time in awhile so maybe you've addressed this, but have you tried a NIST certified sensor?
I hesitate to intrude again on this long-running thread, but isn't the issue here more one of drift from the initial specification over a period of time, whether shorter or longer?
All a NIST sensor from Davis is going to tell you is that when brand new (unless it's a subsequent retest) the RH is confirmed as within ±3% of the reading of some NIST-traceable reference instrument (apparently a General Eastern M4-RH Dew Point Monitor but presumably with some intrinsic error of its own) at 33%; 80% and 90% RH only. Does that really help a lot?
More details in attached PDF. This is the document currently downloadable from Davis but I can't see its original date. Conceivably the tests specs have been tightened since the introduction of SHT31 but there's nothing to indicate that.
I'm pretty sure in his recent posts he was doing experiments with 2 newer acurite sensors and a 5 day old SHT31.
I'm pretty sure in his recent posts he was doing experiments with 2 newer acurite sensors and a 5 day old SHT31.
That would be the shorter period then. :grin: But obviously there may be issues over short-term and then long-term drift, though that's a separate issue. The main point I was aiming at was that NIST certification probably doesn't add much over a random unchecked SHT31, other than to rule out one that was way out of spec, which really shouldn't happen.
What is most irritating is I, and many other folks posting in this Forum, thought by purchasing Davis equipment we were buying the best available in the consumer market.
....
In short, I wish Davis would address these issues or a decent competitor would arrive on the scene.
Thank-you for the well written post johnd, I agree with you. In most manufactured products, the price increase vs quality increase is non-linear. (A station that is .5% more accurate may cost 20 times as much.) When providing feedback to Davis I think we should convey one of the following points: I as a customer/potential customerWhat is most irritating is I, and many other folks posting in this Forum, thought by purchasing Davis equipment we were buying the best available in the consumer market.
....
In short, I wish Davis would address these issues or a decent competitor would arrive on the scene.
But what is the evidence that a VP2 is not 'the best available in the consumer market'? (At least in the sense that there's no better all-round station for performance and capability even if, arguably, some other device may offer better accuracy or whatever in some specific respect - though even there I think hard evidence is lacking, except possibly in respect of rainfall accuracy.)
I'm not particularly looking to defend Davis here, but more making the - fairly obvious - point that it's surely unrealistic to expect higher-end drift-free accuracy at the price-point of a VP2. If a potential competitor felt that there was money to be made from introducing a new range of stations with better all-round performance but at the VP2 price point then surely they would have done so.
But to date this simply hasn't happened, which tends to suggest that it's just not an attractive commercial proposition. VP2-type weather station volumes are in the several thousands per year, not the millions which make innovative mass production much more appealing.
Davis manufactures stations at VP2 prices because it makes it makes some initial design decisions and then sticks with them over extended production periods, with only limited design evolution along the way until a complete new model is released. Anything else would push up the price further.
Don't get me wrong. I think a strong competitor to Davis would be excellent news to drive innovative features and and overall performance of VP2-class station onwards at a faster pace, but equally I can understand the commercial reasons as to why there's no real sign of it happening at present. (Maybe there'll be an announcement of some new wonder station tomorrow even, but I somehow doubt it.) For now, the VP2 IMO represents what is commercially possible at its price point. For users willing to pay substantially more there are other options.
Last update on the Acurite sensor passive in shade still running 8% lower humidity.
Acurite:82-45%
Davis 82-53%
I agree with the above on price point but for anyone living in high heat and high humidity regions getting heat indexes in excess of 120° when it's actually much lower doesn't matter what the price point without reliability.
I don't believe the issue is whether Davis is longer than the other short straws in its segment. It's that they market the station with tight specs.
* What actually is the Sensirion spec for RH drift over time eg 2 years with the SHT31?
I'm north of the 46th parallel. You don't have to get beyond 25C to really notice the issue.
England itself doesn't have deserts, but the UK et.al. does for sure...in Australia!
... I'm still not upgrading until the 3 comes out or I die, ...When/if the 3 comes out I would still wait some time until it has a proven track record. Just look at how a few days or so ago the SHT 31 was being pushed and praised as if it was one of the greatest things ever by the same people who are complaining most vocally now. Even if the 3 comes out, why upgrade if the equipment you have is still working fine? I'm not one who sees every change as being a must-have upgrade.
I guess I don't live around 96+% humidity much, so I really don't care.My view may also be "fogged" by my cool, dry climate.
This is very good news Davis is going to take a serious look.
From Davis tech support:
Hello Randy,
This is of serious concern to us and our engineering team is actively looking in to this. I really appreciate you pushing so hard on this issue. It’s only going to make us better.
I need to give them time to quantify the problem/drift, determine root cause and come up with a solution.
Hmmm. Ok, seems the Davis implementation of the Sht31 sensor isn't optimal and has it's deficiencies. Rather disappointing to find out. :-| As I've mentioned elsewhere, I'm the king of procrastinators and have a 2-year-old Sht31 sensor still in the bubble wrap that I intended to install soon. Now I'm wondering if I should just wait and see what Davis comes up with. Over the last year or so I've noticed the heat indexes have "seemed" elevated more than I recalled them being when the station was newer.
Yesterday I measured (old circa 2013 sensor still in place) a high temperature of 91.5F, looking at a graph the humidity appeared to be 55%...this calculates to a heat index of ~100F. My Davis station reported a heat index of 111.4F. So, even going with the discredited SHT31 assembly, I suppose I should see "some" improvement regarding these numbers...???
My station is now a touch over five years old, so I guess it's expected that the temp/humidity sensor is questionable. I'm one of those living in a high-temperature/high humidity area as are most folks in the southeast part of the USA where the heat index can be fairly important.
Strange that in all the years Davis have been using Sensiron they would not have seen this problem with the stations they have on test at Hayward and out in the field :?
The sensor shows best performance when operated within recommended normal temperature and humidity range of 5 –
60 °C and 20 – 80 %RH, respectively. Long term exposure to conditions outside normal range, especially at high humidity,
may temporarily offset the RH signal (e.g. +3%RH after 60h at >80%RH). After returning into the normal temperature and
humidity range the sensor will slowly come back to calibration state by itself. Prolonged exposure to extreme conditions
may accelerate ageing. To ensure stable operation of the humidity sensor, the conditions described in the document
“SHTxx Assembly of SMD Packages”, section “Storage and Handling Instructions” regarding exposure to volatile organic
compounds have to be met. Please note as well that this does apply not only to transportation and manufacturing, but also
to operation of the SHT3x-ARP.
For exposure to extreme conditions with regards to humidity and temperature please consult the datasheet of respective product. Please make sure that exposure time of the sensor to maximum range of operating conditions is limited as given in datasheet. Exposure to volatile organic compounds at high concentration and long exposure time is critical not only in assembly but also in the field. Such application needs to be carefully tested and qualified.
Reconditioning Procedure
As stated above extreme conditions or exposure to solvent vapors may offset the sensor. The following reconditioning procedure may bring the sensor back to calibration state:
Baking: 100 – 105°C at < 5%RH for 10h
Re-Hydration: 20 – 30°C at ~ 75%RH for 12h 1.
Here's the Gladstone for KHWD.Maybe they just don't look, these aren't necessarily all weather geeks like us watching closely especially me and many on this forum do.
Strange that in all the years Davis have been using Sensiron they would not have seen this problem with the stations they have on test at Hayward and out in the field :?
They were running about +3 DP last time I looked over airport and currently same temperature and + 10% humidity from nearby airport. Really classic example without the high heat. I really don't know exactly where both are located other than Davis is near the water.
Put this in high heat index content and they may have noticed.
I don't recall if all of this has been mentioned... Sensirion has some specific info in their literature and datasheets that is pertinent.
From the datasheet for my analog SHT3x
From their handling instructions PDF:QuoteFor exposure to extreme conditions with regards to humidity and temperature please consult the datasheet of respective product. Please make sure that exposure time of the sensor to maximum range of operating conditions is limited as given in datasheet. Exposure to volatile organic compounds at high concentration and long exposure time is critical not only in assembly but also in the field. Such application needs to be carefully tested and qualified.
My last Acurite check early this morning max humidity at 97%, Davis 96% aspirated so both looking normal.
At 12:40 CT I did a passive shade check against new Davis sensor with 5mph breeze running 7-9% lower humidity so really nothing changed from yesterday.
Not keeping acurite saturated in high humidity outside 24/7 so can't really determine how much drift if any is taking place toward wet side. Max exposure time has been around 2 hours in early morning allowing it to record highest humidity.
My last Acurite check early this morning max humidity at 97%, Davis 96% aspirated so both looking normal.
At 12:40 CT I did a passive shade check against new Davis sensor with 5mph breeze running 7-9% lower humidity so really nothing changed from yesterday.
Not keeping acurite saturated in high humidity outside 24/7 so can't really determine how much drift if any is taking place toward wet side. Max exposure time has been around 2 hours in early morning allowing it to record highest humidity.
Im guessing you’re like me. DPs are 3-4 degrees off being wet in bias
Thread has went about as far as it can go unless anyone has something we didn't cover. Let Davis do their thing and see what they come up with.
Conditions outside the recommended range may
temporarily offset the RH signal up to ±3%RH. After return
to normal conditions it will slowly return close to calibration
state by itself.
To accelerate this process we recommend the following
reconditioning procedure:
90°C at <5%RH for 24h followed by
20-30°C at >74%RH for 48h
Excellent, Randy!!!
This sounds much like renewing silica desiccant, though at a higher temperature. :-k It will be interesting to see whether this improves performance. If it does then it poses the question, for me, of whether I should do this before I install my new/old SHT31.
Thanks for taking the initiative!
Yes, Randy, thank you for running this experiment.
However, the handling and reconditioning instructions prompt me to ask two questions:
1) Why would 2 sensors less than a couple weeks old need "reconditioning"?
2) Why would Davis choose a sensor in which normal environmental conditions for most of its customers would knock it out of calibration not long after purchase (within a year) and require a complicated procedure to remain accurate?
Based on Sensirion's literature, it would appear these sensors are designed for indoor use.
As discussed in several posts before, it is believed Davis has not done a very good job packaging the SHT31 when it leaves the Davis facility and secondly, the white cap that encases the sensor is not very effective in keeping dirt, etc. away from the sensor. Both reasons, if accurate, may give rise to a short life of the SHT31 requiring recalibration.
The sensor shows best performance when operated within recommended normal temperature and humidity range of 5 –
60 °C and 20 – 80 %RH, respectively.
Prolonged exposure to extreme conditions may accelerate ageing.
Only 212F sounds like a plan. I have some of the correct bags non gaseous for Re-Hydration and wet rag.
Reconditioning Procedure
As stated above extreme conditions or exposure to solvent vapors may offset the sensor. The following reconditioning procedure may bring the sensor back to calibration state:
Baking: 100 – 105°C at < 5%RH for 10h
Re-Hydration: 20 – 30°C at ~ 75%RH for 12h 1.
After returning into the normal temperature and humidity range the sensor will slowly come back to calibration state by itself.
Can you pick which option you want to do or do you have to do both for recalibration to take place (if it does)?
I'm in the rehydration phase now maybe I should skip, it may not be necessary because once outside it will get all the moisture it needs plus.
Question: does Acurite have any outdoor weather stations with the SHT31 installed?
Now why would Acurite recently release the Atlas to compete against the VP2 and have a less accurate temperature sensor? It's billed as a "professional" station. Specs I've seen claim +/- 1F. Davis, of course, is +/- 0.5F. Humidity specs are, supposedly, the same. See: https://www.acurite.com/media/documents/AcuRite-Atlas-Elite-Specifications.pdf (https://www.acurite.com/media/documents/AcuRite-Atlas-Elite-Specifications.pdf)
They obviously know about the Sensirion sensor. They put it in their much cheaper indoor-only product. So awareness or cost cannot be the issue.
I would think they'd want to be at least as accurate as their competitor(s) in a certain product segment. They are not. But maybe they decided they didn't want all the warranty headaches that come from putting a sensor best suited for indoor conditions in an outdoor unit. I'm sure there are other considerations as well.
I have the atlas. I also have the 5n1. The humidity is spot on with the Atlas. The temperature is within 1 degree for sure. I hope you guys will try it when it starts being sold. I think you will be very happy with the hardware. I hope the software will continue to offer more, like CWOP uploads because everything is much improved, compared to the 5in1.
For what it's worth, I just took my Belfort 566 psychrometer outside. We are showing 97% RH on my Davis ISS and 95% on the Davis Temp/Hum station. I believe that these are both SHT-11 (or -15) and definitely not SHT-31.
Using distilled water I got 65°F dry bulb and 64°F wet bulb.
The slide rule shows about 94% RH a web calculator gives 94.88% RH. http://linricsoftw.web701.discountasp.net/webpsycalc.aspx (http://linricsoftw.web701.discountasp.net/webpsycalc.aspx)
I ordered one of those Sensirion SHT-31 eval boards from Mouser.
Greg H.
Reconditioning I'm seeing no change so I'm scrapping that idea.
Davis units still running +9% humidity and +4dp vs Acurite.
The directions on Acurite say you can manually calibrate but pulling batteries and reinstall resets calibration. I've never messed with any calibration. I don't know if Acurite has asked for different calibration vs the Davis from factory or if it's even possible, but dp temps on Acurite run very close to airport.
test results after recondition dp temps were as follows
all 3-sht31's -69°
Acurite -65°
ASOS 1.3 miles away -65°
I just don't know #-o.
To be fair, the humidity is currently running around 90-91% here after some rain. That's not where the Davis sensors tend to be problematic. The true test in performance will be once humidity drops below 70%.Maybe Davis should market the 31 as an arid climate only sensor as both my 31's have no issues here, or really anywhere for that matter.
Reconditioning I'm seeing no change so I'm scrapping that idea.
Davis units still running +9% humidity and +4dp vs Acurite.
The directions on Acurite say you can manually calibrate but pulling batteries and reinstall resets calibration. I've never messed with any calibration. I don't know if Acurite has asked for different calibration vs the Davis from factory or if it's even possible, but dp temps on Acurite run very close to airport.
test results after recondition dp temps were as follows
all 3-sht31's -69°
Acurite -65°
ASOS 1.3 miles away -65°
I just don't know #-o.
Bummer. Thank you for trying it out and letting us know. But if you take the rehydration part out of the equation and just install the unit back outside, would it make any difference?
I posted this earlier and I'm sure I got a :roll: from every member here, but I use this to clean my sensors and always have. Just did both of them a few days ago. Probably won't help, but who knows? Whatta ya got to lose, an already bad sensor??
http://www.acehardware.com/product/index.jsp?productId=1451535
I posted this earlier and I'm sure I got a :roll: from every member here, but I use this to clean my sensors and always have. Just did both of them a few days ago. Probably won't help, but who knows? Whatta ya got to lose, an already bad sensor??
http://www.acehardware.com/product/index.jsp?productId=1451535
I posted this earlier and I'm sure I got a :roll: from every member here, but I use this to clean my sensors and always have. Just did both of them a few days ago. Probably won't help, but who knows? Whatta ya got to lose, an already bad sensor??
http://www.acehardware.com/product/index.jsp?productId=1451535
Wonder if Sensirion approves? Here's it's MSDS: http://s7d9.scene7.com/is/content/GenuinePartsCompany/683483pdf?$PDF$ (http://s7d9.scene7.com/is/content/GenuinePartsCompany/683483pdf?$PDF$)
Don't care.....I posted this earlier and I'm sure I got a :roll: from every member here, but I use this to clean my sensors and always have. Just did both of them a few days ago. Probably won't help, but who knows? Whatta ya got to lose, an already bad sensor??
http://www.acehardware.com/product/index.jsp?productId=1451535
Wonder if Sensirion approves? Here's it's MSDS: http://s7d9.scene7.com/is/content/GenuinePartsCompany/683483pdf?$PDF$ (http://s7d9.scene7.com/is/content/GenuinePartsCompany/683483pdf?$PDF$)
Yeah, that's how I killed my SHT11, 15 and two 31's that work, that all have been getting the treatment for 10 years.I posted this earlier and I'm sure I got a :roll: from every member here, but I use this to clean my sensors and always have. Just did both of them a few days ago. Probably won't help, but who knows? Whatta ya got to lose, an already bad sensor??
http://www.acehardware.com/product/index.jsp?productId=1451535
WE can always just subtract 6-9% humidity and be normal. But will read really low in the morning when it's near 100% almost daily. Or :idea: kill the sensor with chemical spray.. Let's see which one... :-(
I had to remove a post I just made. Sorry about that if you came here to read it. It contained some incorrect information.I'm gonna guess that the ONLY differences between SHT-11, -15, and -31 are tighter & better production and quality control during fabrication because the basic "science" of mylar polyester capacitive sensors has NOT changed much since mylar was invented back in the 1950's.
I just found that the SHT1x datasheet has the same language about optimal operating conditions and premature aging as the SHT3x. Although, that might explain the anomalous results posted by Stephen Burt in his 2009 review of the humidity sensor for the VP2 (running the SHT11). Looks like his unit, that was less than a year old, was running high by 5-6% in the middle ranges pretty consistently. I've got the 15 set up now and I'm just waiting for humidity to come down so I can see if it's still in calibration after over a year of wear & tear not to mention 18 months in storage.
I had to remove a post I just made. Sorry about that if you came here to read it. It contained some incorrect information.I'm gonna guess that the ONLY differences between SHT-11, -15, and -31 are tighter & better production and quality control during fabrication...the basic "science" of mylar polyester capacitive sensors has NOT changed much since mylar was invented back in the 1950's.
I just found that the SHT1x datasheet has the same language about optimal operating conditions and premature aging as the SHT3x. Although, that might explain the anomalous results posted by Stephen Burt in his 2009 review of the humidity sensor for the VP2 (running the SHT11). Looks like his unit, that was less than a year old, was running high by 5-6% in the middle ranges pretty consistently. I've got the 15 set up now and I'm just waiting for humidity to come down so I can see if it's still in calibration after over a year of wear & tear not to mention 18 months in storage.
The weather station market is so small that companies are not going to manufacture a humidity sensor with specs just for weather stations. Most humidity sensors are designed for indoor use. One of their biggest uses is for HVAC duct testing. That includes the Sensirion sensors.Let me edit that: "If Davis were to use it in the VP2 the
As I said earlier in the thread, the SHT-31 was not designed for meteorological use and that should be obvious by its limited normal operating temperature and humidity ranges. But those limited operating ranges are normal for humidity sensors because again, they are not designed for meteorological applications. Davis must have felt that this was the best sensor to do the job even though it was not designed for meteorological applications.
I only know of one humidity sensor that is designed for meteorological applications. That is the one I use at home, the Vaisala HMT337. From the Vaisala literature it states:
HMT337 Configurations
Vaisala HUMICAP Humidity and Temperature Transmitter
HMT337 is ideal for the most demanding process and meteorological measurements in high-humidity condensing environments.
It is a rock solid sensor across the board. If Davis were to use it in the VP2 the cost of the station would probably double.
The weather station market is so small that companies are not going to manufacture a humidity sensor with specs just for weather stations. Most humidity sensors are designed for indoor use. One of their biggest uses is for HVAC duct testing. That includes the Sensirion sensors.
As I said earlier in the thread, the SHT-31 was not designed for meteorological use and that should be obvious by its limited normal operating temperature and humidity ranges. But those limited operating ranges are normal for humidity sensors because again, they are not designed for meteorological applications. Davis must have felt that this was the best sensor to do the job even though it was not designed for meteorological applications.
I only know of one humidity sensor that is designed for meteorological applications. That is the one I use at home, the Vaisala HMT337. From the Vaisala literature it states:
HMT337 Configurations
Vaisala HUMICAP Humidity and Temperature Transmitter
HMT337 is ideal for the most demanding process and meteorological measurements in high-humidity condensing environments.
It is a rock solid sensor across the board. If Davis were to use it in the VP2 the cost of the station would probably double.
The only other option that Davis has (in terms of using a cheap chip) is this sensor that was mentioned by hwcorder (which is supposedly designed for high humidities).
https://www.ist-ag.com/en-us/products/hyt-221-calibrated-and-temperature-compensated
The only other option that Davis has (in terms of using a cheap chip) is this sensor that was mentioned by hwcorder (which is supposedly designed for high humidities).
https://www.ist-ag.com/en-us/products/hyt-221-calibrated-and-temperature-compensated
How would they marry that to Sensibus? Also, it's listed as "currently not in stock" by the manufacturer.
The weather station market is so small that companies are not going to manufacture a humidity sensor with specs just for weather stations. Most humidity sensors are designed for indoor use. One of their biggest uses is for HVAC duct testing. That includes the Sensirion sensors.
As I said earlier in the thread, the SHT-31 was not designed for meteorological use and that should be obvious by its limited normal operating temperature and humidity ranges. But those limited operating ranges are normal for humidity sensors because again, they are not designed for meteorological applications. Davis must have felt that this was the best sensor to do the job even though it was not designed for meteorological applications.
I only know of one humidity sensor that is designed for meteorological applications. That is the one I use at home, the Vaisala HMT337. From the Vaisala literature it states:
HMT337 Configurations
Vaisala HUMICAP Humidity and Temperature Transmitter
HMT337 is ideal for the most demanding process and meteorological measurements in high-humidity condensing environments.
It is a rock solid sensor across the board. If Davis were to use it in the VP2 the cost of the station would probably double.
Saw this on Sparkfun today.
Hygrometers: A Cautionary Tale
Our (kinda) epic journey about learning the proper way to handle humidity sensors.
https://www.sparkfun.com/news/1090
Humidity Sensors make use of a conductive polymer to measure relative humidity. If that polymer
gets too dry (or over-saturated) the sensor won't function properly, but that can be reversed.
Whenever we use one of these sensors on our designs, we put them through a re-conditioning
procedure to ensure that they keep their factory calibration. If you expose your sensor to a really dry
environment for a prolonged period of time (or saturate it with water) you may have to run it through
the same process.
https://cdn.sparkfun.com/datasheets/Sensors/Weather/Hygrometer_ReCon.pdf
How did your reconditioned humidity sensor do this morning?
The weather station market is so small that companies are not going to manufacture a humidity sensor with specs just for weather stations. Most humidity sensors are designed for indoor use. One of their biggest uses is for HVAC duct testing. That includes the Sensirion sensors.
As I said earlier in the thread, the SHT-31 was not designed for meteorological use and that should be obvious by its limited normal operating temperature and humidity ranges. But those limited operating ranges are normal for humidity sensors because again, they are not designed for meteorological applications. Davis must have felt that this was the best sensor to do the job even though it was not designed for meteorological applications.
I only know of one humidity sensor that is designed for meteorological applications. That is the one I use at home, the Vaisala HMT337. From the Vaisala literature it states:
HMT337 Configurations
Vaisala HUMICAP Humidity and Temperature Transmitter
HMT337 is ideal for the most demanding process and meteorological measurements in high-humidity condensing environments.
It is a rock solid sensor across the board. If Davis were to use it in the VP2 the cost of the station would probably double.
As stated before, variablilty is the norm with the SHT31. Currently (8pm):
New station (24 hour fan)—T 71, H 84
2 year old station (daytime fan)—T 72, H 79
2.5 year old station (daytime fan)—T 72, H 82.
As stated before, variablilty is the norm with the SHT31. Currently (8pm):
New station (24 hour fan)—T 71, H 84
2 year old station (daytime fan)—T 72, H 79
2.5 year old station (daytime fan)—T 72, H 82.
So your new station runs the wettest?
If so, then Randy's 2 new out-of-spec sensors are not a fluke. That would begin to point toward a raft of defective sensors currently for sale.
Or was the point that all 3 sensors trade places in terms of accuracy?
The Atlas uses a Sensirion SHT31 temp/humidity chip. This is an upgrade from the SHT21 used in the 5n1.
Maybe using the SHT31?
Found another Atlas (https://www.wunderground.com/personal-weather-station/dashboard?ID=KOHBEDFO15 (https://www.wunderground.com/personal-weather-station/dashboard?ID=KOHBEDFO15)). It's reporting dew point of 69 and nearby airports are reporting 60-63.
Maybe using the SHT31?Would the Vaisala sensor work with a Davis?
Someone needs to find a better sensor that's accurate, I'm not sold on any of the Sensirion sensors for meteorological use now even the 15 had high bias just not as bad but also never went above 95%.
Maybe using the SHT31?
Someone needs to find a better sensor that's accurate, I'm not sold on any of the Sensirion sensors for meteorological use now even the 15 had high bias just not as bad but also never went above 95%.
Maybe using the SHT31?Would the Vaisala sensor work with a Davis?
Someone needs to find a better sensor that's accurate, I'm not sold on any of the Sensirion sensors for meteorological use now even the 15 had high bias just not as bad but also never went above 95%.
Maybe using the SHT31?
Someone needs to find a better sensor that's accurate, I'm not sold on any of the Sensirion sensors for meteorological use now even the 15 had high bias just not as bad but also never went above 95%.
So...MAYBE...we're gonna have to chose between:
- top-end limited, somewhat accurate, SHT-15
- top-end capable, somewhat accurate, SHT-31
I'm wondering if some software can't fix this issue.
I don't know enough about how they put code in sensor but I've got 2-SHT31's by Acurite that doesn't display the high bias just the opposite almost right with the airport all the time.
What did they do different with these $15 dollar units vs their new Atlas running high also? Maybe they didn't realize there was an issue. Looks like they are following Davis even having aspiration by fan, maybe they thought everything was good.
Yes, I was thinking the same thing. Maybe a software update would correct the wet bias.
Another thought. I wonder how the Visalia probe would perform in the 24 hour FARS?
I'm wondering if some software can't fix this issue.
I don't know enough about how they put code in sensor but I've got 2-SHT31's by Acurite that doesn't display the high bias just the opposite almost right with the airport all the time.
What did they do different with these $15 dollar units vs their new Atlas running high also? Maybe they didn't realize there was an issue. Looks like they are following Davis even having aspiration by fan, maybe they thought everything was good.
Maybe that’s what RW did. They probably pregammed the console to correct the inaccuracies of the SHT-15 in certain humidity ranges.
Maybe that’s what RW did. They probably pregammed the console to correct the inaccuracies of the SHT-15 in certain humidity ranges.
Randy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
Randy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
YesRandy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
Correct me if I'm wrong, Randy, but didn't you say that your 15s were fried too when it came to humidity?
This is interesting...drier air moved into central Alabama today.
Airport that is 15 miles N of me. 88/64
Acurite Temp/Hum sensor with lightning detector 89/65.5
Davis VP 2 with -8% offset 88/67.7
This is interesting...drier air moved into central Alabama today.
Airport that is 15 miles N of me. 88/64
Acurite Temp/Hum sensor with lightning detector 89/65.5
Davis VP 2 with -8% offset 88/67.7
This is interesting...drier air moved into central Alabama today.
Airport that is 15 miles N of me. 88/64
Acurite Temp/Hum sensor with lightning detector 89/65.5
Davis VP 2 with -8% offset 88/67.7
So chasing humidity too.... :sad:
The 75 is basically a 15 with slightly better RH specs between 10-90% (1.8% versus 2.0%). The difference is that it is presoldered by Sensirion. Solder the correct wires to an old 6-conductor Davis temp/hum and it becomes plug and play. With your FARS the temp response will be through the roof because of the low thermal mass...especially if you run it with the filter off.Randy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
So remove sht15 chip and solder SHT75 in its place? How is the 75 with humidity? Does it have the same high bias even after reconditioning the 31 nothing really changed.
YesRandy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
Correct me if I'm wrong, Randy, but didn't you say that your 15s were fried too when it came to humidity?
Yes it's not much better.
This is interesting...drier air moved into central Alabama today.
Airport that is 15 miles N of me. 88/64
Acurite Temp/Hum sensor with lightning detector 89/65.5
Davis VP 2 with -8% offset 88/67.7
So chasing humidity too.... :sad:
Dewpoint (DP) is calculated from the TEMP and RH values, so if either one is off, so too will be the calculated DP value. However, TEMP is usually far more accurate than RH, so DP errors can usually be traced back to the errant RH values more than TEMP values.
This is interesting...drier air moved into central Alabama today.
Airport that is 15 miles N of me. 88/64
Acurite Temp/Hum sensor with lightning detector 89/65.5
Davis VP 2 with -8% offset 88/67.7
Yikes! By my calculations that's a >20% absolute humidity error, assuming the dew point of 67.7 is actually 75.7 without the offset.
I forgot to put in my little acurite is showing 86/64 humidity is way off for a 31 sensor chip.
I forgot to put in my little acurite is showing 86/64 humidity is way off for a 31 sensor chip.
Because it's not reading high? My 2 acurite units are normal on humidity.
No because it is reading lower than all the other sensors i have, by 5% or more. I guess i will have to put it in the bag and see how close it comes to 75%.
I forgot to put in my little acurite is showing 86/64 humidity is way off for a 31 sensor chip.
Because it's not reading high? My 2 acurite units are normal on humidity.
Have you thought about, perhaps, leaving one of them outside in the shade during days without precipitation? I wonder how long it would stay in calibration?
I put mine out when light fog was expected and it pegged out at 99 and main station was reporting 97 and that was the general high for around the area. Not too impressed with my cheap meter, i might have to take it apart and see if it does have a 31 and how it is mounted.
From my testing the Davis sensors all read high. I didn't use a bag but going from my other instruments and ASOS the acurite is correct.
That was my point how can I have 2 acurite sht31's read normal with instruments and ASOS and then have 3 Davis sensors all high.
That's where the idea of contamination came in with 2 different companies mounting differently onto boards.
The 75 is basically a 15 with slightly better RH specs between 10-90% (1.8% versus 2.0%). The difference is that it is presoldered by Sensirion. Solder the correct wires to an old 6-conductor Davis temp/hum and it becomes plug and play. With your FARS the temp response will be through the roof because of the low thermal mass...especially if you run it with the filter off.Randy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
So remove sht15 chip and solder SHT75 in its place? How is the 75 with humidity? Does it have the same high bias even after reconditioning the 31 nothing really changed.
YesRandy...
I brought it up before, but have you ever tried an SHT75? If you're really suspicious about Davis' handling of the sensors it may be worth giving a sensor soldered at the Sensirion factory a try. I'm sure you have an old Davis SHTxx that you can sacrifice to solder directly to the 75 pins or insert into an acceptable connector.
Correct me if I'm wrong, Randy, but didn't you say that your 15s were fried too when it came to humidity?
Yes it's not much better.
http://www.wxforum.net/index.php?topic=14175.msg189484#msg189484
http://www.mouser.com/ds/2/682/Sensirion_Humidity_SHT7x_Datasheet_V5-469726.pdf
I have a few of these and a new 75 coming in tomorrow from Newark. They should work. We'll find out tomorrow. No soldering required.
http://www.newark.com/harting/14310410301000/receptacle-4way-1row-1-27mm-har/dp/53X2803
I know this may be getting off subject a little but for those interested in switching software from WL or Cumulus over to Weather Display.... WD has a nice slope adjustment that would work. I just downloaded and impressed, my biggest problem I have 4 years of data on Cumulus and website data all using Cumulus lot's of work to change over.
Anyway the slope adjustment at -3% looks like it would work, here's the PDF. I tried it out and works.
There is a setting for decreasing slope as humidity drops lower end of scale also which I have checked. It doesn't show on PDF however.
Read the first few pages of this thread...specifically this post.I know this may be getting off subject a little but for those interested in switching software from WL or Cumulus over to Weather Display.... WD has a nice slope adjustment that would work. I just downloaded and impressed, my biggest problem I have 4 years of data on Cumulus and website data all using Cumulus lot's of work to change over.
Anyway the slope adjustment at -3% looks like it would work, here's the PDF. I tried it out and works.
There is a setting for decreasing slope as humidity drops lower end of scale also which I have checked. It doesn't show on PDF however.
Nice! Personally don’t care for WD. I personally don’t want to keep doing calibration offsets etc. I’m thinking about giving the 75 a try if I can set everything up without soldering. I’m hoping someone on here can tell me how to install the SHT-75. And I’m also curious too if the 75 needs a filter cap?
Read the first few pages of this thread...specifically this post.I know this may be getting off subject a little but for those interested in switching software from WL or Cumulus over to Weather Display.... WD has a nice slope adjustment that would work. I just downloaded and impressed, my biggest problem I have 4 years of data on Cumulus and website data all using Cumulus lot's of work to change over.
Anyway the slope adjustment at -3% looks like it would work, here's the PDF. I tried it out and works.
There is a setting for decreasing slope as humidity drops lower end of scale also which I have checked. It doesn't show on PDF however.
Nice! Personally don’t care for WD. I personally don’t want to keep doing calibration offsets etc. I’m thinking about giving the 75 a try if I can set everything up without soldering. I’m hoping someone on here can tell me how to install the SHT-75. And I’m also curious too if the 75 needs a filter cap?
http://www.wxforum.net/index.php?topic=14175.msg138241#msg138241
Sensirion makes a filter for it, but you need a way to make it fit and stay secure. I have run mine no filter, but that will obviously degrade performance with time. I don't have much time this morning...maybe more later.
Ok got to try make this short lol. After 12 hrs in the bag the acurite, as expected, showed 71% which is 4 low. I calibrated to 75 and put it outside in the light fog at the time. My main station was showing 98% the acurite went up slowly to 98 and stayed there for some time before going to 99. Looks pretty good. Now i put the acurite in unused room and let it settle in to 62% and steady and put the 3 old 31 and the new 31 and let them settle in. One read 1% low, two of them read 3% high and one was right on. So i took the one that was showing 1 low and bagged it for a while and it showed to be 73.7% which is right at 1 low and right now is showing 61% next to acurite which still shows 62%. I bagged the one right on an it showed 75.3% and it shows the same as the acurite. I have not check the two that have 3% high but probably will check one though it sure looks like they will be high on the bag test. 3% high is not within specs.
Right now i am looking at comparing readings at a given calibration point. I have a 33% packet for testing and i also have potassium sulfate for a 97% reference. My real pain is that the brand new 31 is 3% high to start.
Ok. Thanks!Just remember that you don't need the capacitor for the SHT75 since it's preinstalled. That post I referenced was for the SHT15. You just need to worry about the proper wiring.
I dug my old Weather Monitor II station out few days ago to hook up the temp/hum sensor to compare to my sht31 vp2.
Even after all these years the dewpoints last few days were constantly close to those of nearby weather service station than the vp2.
Finally today the humidity fell below 70% and I was able to test the midrange on the SHT15. Not good. I'm seeing an average dew point error of about 2-3 degrees F (54F on my good 31 vs 57F on my bad 15). That's a 5-7% humidity difference. So, it appears my 15 has succumbed to the same problem as other Davis sensors. It reads wetter with time (it's about 3 years old now). My guess, based on past experience with this problem, is that as humidity descends toward 50% and/or the air temp goes up the errors will worsen.
Finally today the humidity fell below 70% and I was able to test the midrange on the SHT15. Not good. I'm seeing an average dew point error of about 2-3 degrees F (54F on my good 31 vs 57F on my bad 15). That's a 5-7% humidity difference. So, it appears my 15 has succumbed to the same problem as other Davis sensors. It reads wetter with time (it's about 3 years old now). My guess, based on past experience with this problem, is that as humidity descends toward 50% and/or the air temp goes up the errors will worsen.
I’m now curious how a new SHT-75 will perform overall. Are you thinking about getting the 75?
Read the first few pages of this thread...specifically this post.I know this may be getting off subject a little but for those interested in switching software from WL or Cumulus over to Weather Display.... WD has a nice slope adjustment that would work. I just downloaded and impressed, my biggest problem I have 4 years of data on Cumulus and website data all using Cumulus lot's of work to change over.
Anyway the slope adjustment at -3% looks like it would work, here's the PDF. I tried it out and works.
There is a setting for decreasing slope as humidity drops lower end of scale also which I have checked. It doesn't show on PDF however.
Nice! Personally don’t care for WD. I personally don’t want to keep doing calibration offsets etc. I’m thinking about giving the 75 a try if I can set everything up without soldering. I’m hoping someone on here can tell me how to install the SHT-75. And I’m also curious too if the 75 needs a filter cap?
http://www.wxforum.net/index.php?topic=14175.msg138241#msg138241
Sensirion makes a filter for it, but you need a way to make it fit and stay secure. I have run mine no filter, but that will obviously degrade performance with time. I don't have much time this morning...maybe more later.
I'm still doing fine. Just throwing the disclaimer out there.Read the first few pages of this thread...specifically this post.I know this may be getting off subject a little but for those interested in switching software from WL or Cumulus over to Weather Display.... WD has a nice slope adjustment that would work. I just downloaded and impressed, my biggest problem I have 4 years of data on Cumulus and website data all using Cumulus lot's of work to change over.
Anyway the slope adjustment at -3% looks like it would work, here's the PDF. I tried it out and works.
There is a setting for decreasing slope as humidity drops lower end of scale also which I have checked. It doesn't show on PDF however.
Nice! Personally don’t care for WD. I personally don’t want to keep doing calibration offsets etc. I’m thinking about giving the 75 a try if I can set everything up without soldering. I’m hoping someone on here can tell me how to install the SHT-75. And I’m also curious too if the 75 needs a filter cap?
http://www.wxforum.net/index.php?topic=14175.msg138241#msg138241
Sensirion makes a filter for it, but you need a way to make it fit and stay secure. I have run mine no filter, but that will obviously degrade performance with time. I don't have much time this morning...maybe more later.
Just wondering cause I'm all about accuracy, how would you really know the sensor is degrading, slower response times? Also, I know you run a 40 cfm fan, but with no filter that has really got to be doing a huge number on your sensor without the filter on. You probably have to change out your sensor about every month, no?
I don't own any Davis SHT31 sensors, but have a few I2C SHT3x sensors in operation in various fan aspirated shields. I haven't done any scientific comparisons, but I am not seeing any significant difference in the humidity readings.
Yesterday the lowest humidity for the day was around 17:40.
SHT31, 22 months old, no protective cover: 41.90%
SHT35, 15 months old, Davis cap: 41.97%
3kms away I have another station:
SHT35, 5 months old, SF2 cap: 41.26%
At this time the closest meteorology bureau station was reading 41%.
So maybe the analog versions of the sensors are the bad ones?
How does the 35 & 31 compare when it comes to humidities in the upper 90 percentile? How do they compare in terms of air temp?
I have followed this forum for years, but never registered or even really considered posting. I have learned a great deal from following all of your comments and experiences over the years. So let me start by saying thank you. This particular topic, however, has brought me out of the shadows …
I have owned Davis equipment since 2005. I bought a VP2. In 2006, I moved to south Texas and upgraded to a 24hr FARS and this is where my frustration with the dew point readings of the VP2 began. My new sensor would never hit 100% humidity and the rest of the scale had a wet bias, but my VP2 from 2005 never had these issues. My 2006 VP2 with FARS had an SHT11 and my 2005 had the old "analog" sensor.
I am no expert obviously, just another guy with a borderline unhealthy obsession with this stuff, but bottom line: my opinion and experience strongly supports that despite the inherent limitation of the Sensirion sensors, there is something about Davis' manufacturing process that causes an offset toward a wet bias.
I have been obsessed with trying to fix and find the source of this bias as well as trying to find a sensor that consistently hits 100% RH. The SHT11 had these issues and disappointingly so did the SHT31. I have moved around a bunch, so I have tested these things from anywhere from Texas to Maine to DC and to the Pacific Northwest. The result has always been the same. I have spent hours over the years with my sensors within 10 feet from the HO-1088 and DTS1 of an ASOS. I have purchased a psychro-dyne for quality checking. I have had the sensors in the -20sF in Maine and Vermont and over 100F in DC and Texas. Here are the main points of what I have learned:
-Outgassing of silicon and glue offsets the Sensirion sensor. The offset seems irreversible. Silicon offsets to the high side. Some glues to the low side. (I discovered this trying to use Sensirion's own filters instead of Davis' filter.)
-The Davis filter may increase response time, but is not responsible for the wet bias.
-The Sensirion sensors do seem to have a slight wet bias as has been documented in some studies, but this wet bias is some how exacerbated by how Davis mounts the sensor.
-The wet bias for Sensirion sensors in prolonged periods near saturation as mentioned in their datasheet is a separate issue from the wet bias created by the Davis mounting.
-The SHT75 straight from the manufacturer without any filter is superior to the Davis mounted SHT31 in terms of dew point and humidity.
-The SHT75 will hit up to 99%, with random very short lived jumps to 100%.
-I miss the old analog sensor
I currently run my station with an SHT75 with no filter at all. I've been doing it for about 6mos. The first 5 of those months were in a stock Davis 24hr FARS. Now it is in the Davis 7714, which is a surprisingly good passive shield (much better than the VP2 stock passive shield) (sometimes a degree or two cooler than the FARS, sometimes a degree or two warmer, at least in the north latitudes of the Seattle area...) I am concerned with contamination and dust, but after trying to put a filter on it with silicon and other glues, I have ruined a fair number of SHT75s with seemingly irreversible offsets. So far I have not seen any evidence of poor performance for lack of a filter.
I run a calibration in Cumulus for the SHT75 (1.041x-3) and field check it with the psychro-dyne. It generally is very close. The psychro-dyne is surprisingly accurate compared side by side to ASOS. I set Cumulus to report 98% as 100% and the calibration I set ensures 99% is reported as 100% too.
This is the best I have been able to do given the limitations of these sensors. I really hope the efforts here will force Davis to look at their process as I'd be happy to have an accurate Davis stock sensor that is engineered to last.
Hope this helps...
I don't *believe* that the Davis sensor is analog. I've inquired about this before because I, too, assumed it must be using one of Sensirion's analog solutions and was told by someone knowledgeable that Sensibus is a digital-only platform. johnd should know.
I have followed this forum for years, but never registered or even really considered posting. I have learned a great deal from following all of your comments and experiences over the years. So let me start by saying thank you. This particular topic, however, has brought me out of the shadows …Nice first post. My observations tend to align with yours. We have fairly close CWOP IDs so we both got our VP2s when the Davis analog sensor was nearing its final days. That thing hit 100% so often that I was afraid it was hitting it too much. On a radiational cooling night I'd hit 100% around 9pm and it would flatline there until about 8-9am.
I have owned Davis equipment since 2005. I bought a VP2. In 2006, I moved to south Texas and upgraded to a 24hr FARS and this is where my frustration with the dew point readings of the VP2 began. My new sensor would never hit 100% humidity and the rest of the scale had a wet bias, but my VP2 from 2005 never had these issues. My 2006 VP2 with FARS had an SHT11 and my 2005 had the old "analog" sensor.
I am no expert obviously, just another guy with a borderline unhealthy obsession with this stuff, but bottom line: my opinion and experience strongly supports that despite the inherent limitation of the Sensirion sensors, there is something about Davis' manufacturing process that causes an offset toward a wet bias.
I have been obsessed with trying to fix and find the source of this bias as well as trying to find a sensor that consistently hits 100% RH. The SHT11 had these issues and disappointingly so did the SHT31. I have moved around a bunch, so I have tested these things from anywhere from Texas to Maine to DC and to the Pacific Northwest. The result has always been the same. I have spent hours over the years with my sensors within 10 feet from the HO-1088 and DTS1 of an ASOS. I have purchased a psychro-dyne for quality checking. I have had the sensors in the -20sF in Maine and Vermont and over 100F in DC and Texas. Here are the main points of what I have learned:
-Outgassing of silicon and glue offsets the Sensirion sensor. The offset seems irreversible. Silicon offsets to the high side. Some glues to the low side. (I discovered this trying to use Sensirion's own filters instead of Davis' filter.)
-The Davis filter may increase response time, but is not responsible for the wet bias.
-The Sensirion sensors do seem to have a slight wet bias as has been documented in some studies, but this wet bias is some how exacerbated by how Davis mounts the sensor.
-The wet bias for Sensirion sensors in prolonged periods near saturation as mentioned in their datasheet is a separate issue from the wet bias created by the Davis mounting.
-The SHT75 straight from the manufacturer without any filter is superior to the Davis mounted SHT31 in terms of dew point and humidity.
-The SHT75 will hit up to 99%, with random very short lived jumps to 100%.
-I miss the old analog sensor
I currently run my station with an SHT75 with no filter at all. I've been doing it for about 6mos. The first 5 of those months were in a stock Davis 24hr FARS. Now it is in the Davis 7714, which is a surprisingly good passive shield (much better than the VP2 stock passive shield) (sometimes a degree or two cooler than the FARS, sometimes a degree or two warmer, at least in the north latitudes of the Seattle area...) I am concerned with contamination and dust, but after trying to put a filter on it with silicon and other glues, I have ruined a fair number of SHT75s with seemingly irreversible offsets. So far I have not seen any evidence of poor performance for lack of a filter.
I run a calibration in Cumulus for the SHT75 (1.041x-3) and field check it with the psychro-dyne. It generally is very close. The psychro-dyne is surprisingly accurate compared side by side to ASOS. I set Cumulus to report 98% as 100% and the calibration I set ensures 99% is reported as 100% too.
This is the best I have been able to do given the limitations of these sensors. I really hope the efforts here will force Davis to look at their process as I'd be happy to have an accurate Davis stock sensor that is engineered to last.
Hope this helps...
Nice post, CW7491! This is why the thread exists - so people can share their experiences and knowledge.I just wiretie the cord to the temp/hum mounting plate.
Couple questions:
1) How do you mount the 75 to the shield if you don't use glue or silicon?
2) Approximately how long did your previous 75s last before they went off the rails?
I don't *believe* that the Davis sensor is analog. I've inquired about this before because I, too, assumed it must be using one of Sensirion's analog solutions and was told by someone knowledgeable that Sensibus is a digital-only platform. johnd should know.
No, I don't know with 100% certainty I'm afraid - that level of detail would only be known within Davis Engineering.
But to the absolute best of my knowledge, Davis have only ever used (what seems to be referred to as) Sensibus or Sbus - ie digital - versions of the SHT series of T/H sensors in eg the post 2006 VP2 stations. So any thought of analogue would be - I strongly suspect - completely wide of the mark.
I've never been bothered to look into it in sufficient detail, but don't the markings on the sensor reveal its type/subtype etc? They're tiny and you probably need to take a good photo and enlarge appropriately and then cross-check with the detailed Sensirion documentation.
SHT3x-LSS datasheetI don't *believe* that the Davis sensor is analog. I've inquired about this before because I, too, assumed it must be using one of Sensirion's analog solutions and was told by someone knowledgeable that Sensibus is a digital-only platform. johnd should know.
No, I don't know with 100% certainty I'm afraid - that level of detail would only be known within Davis Engineering.
But to the absolute best of my knowledge, Davis have only ever used (what seems to be referred to as) Sensibus or Sbus - ie digital - versions of the SHT series of T/H sensors in eg the post 2006 VP2 stations. So any thought of analogue would be - I strongly suspect - completely wide of the mark.
I've never been bothered to look into it in sufficient detail, but don't the markings on the sensor reveal its type/subtype etc? They're tiny and you probably need to take a good photo and enlarge appropriately and then cross-check with the detailed Sensirion documentation.
I’ve heard that the version of the SHT-31 that Davis uses is the “analog.” That’s why I said it but I’m probably not correct in calling it analog.
If someone on here knows how alter the Davis transmitter so that it can take a SHT-35 would be awesome! I also might add that I would be willing to buy a SHT-35 from someone who knows how to make the SHT-35 sensor that will fit into the Davis 24hr FARS & passive shields.
SHT3x-LSS datasheetI don't *believe* that the Davis sensor is analog. I've inquired about this before because I, too, assumed it must be using one of Sensirion's analog solutions and was told by someone knowledgeable that Sensibus is a digital-only platform. johnd should know.
No, I don't know with 100% certainty I'm afraid - that level of detail would only be known within Davis Engineering.
But to the absolute best of my knowledge, Davis have only ever used (what seems to be referred to as) Sensibus or Sbus - ie digital - versions of the SHT series of T/H sensors in eg the post 2006 VP2 stations. So any thought of analogue would be - I strongly suspect - completely wide of the mark.
I've never been bothered to look into it in sufficient detail, but don't the markings on the sensor reveal its type/subtype etc? They're tiny and you probably need to take a good photo and enlarge appropriately and then cross-check with the detailed Sensirion documentation.
I’ve heard that the version of the SHT-31 that Davis uses is the “analog.” That’s why I said it but I’m probably not correct in calling it analog.
If someone on here knows how alter the Davis transmitter so that it can take a SHT-35 would be awesome! I also might add that I would be willing to buy a SHT-35 from someone who knows how to make the SHT-35 sensor that will fit into the Davis 24hr FARS & passive shields.
https://www.glynshop.com/erp/owweb/Daten/Datenblaetter/Sensirion/SHT3x_LSS_V0.94.pdf
SHT3x-LSS datasheetI don't *believe* that the Davis sensor is analog. I've inquired about this before because I, too, assumed it must be using one of Sensirion's analog solutions and was told by someone knowledgeable that Sensibus is a digital-only platform. johnd should know.
No, I don't know with 100% certainty I'm afraid - that level of detail would only be known within Davis Engineering.
But to the absolute best of my knowledge, Davis have only ever used (what seems to be referred to as) Sensibus or Sbus - ie digital - versions of the SHT series of T/H sensors in eg the post 2006 VP2 stations. So any thought of analogue would be - I strongly suspect - completely wide of the mark.
I've never been bothered to look into it in sufficient detail, but don't the markings on the sensor reveal its type/subtype etc? They're tiny and you probably need to take a good photo and enlarge appropriately and then cross-check with the detailed Sensirion documentation.
I’ve heard that the version of the SHT-31 that Davis uses is the “analog.” That’s why I said it but I’m probably not correct in calling it analog.
If someone on here knows how alter the Davis transmitter so that it can take a SHT-35 would be awesome! I also might add that I would be willing to buy a SHT-35 from someone who knows how to make the SHT-35 sensor that will fit into the Davis 24hr FARS & passive shields.
https://www.glynshop.com/erp/owweb/Daten/Datenblaetter/Sensirion/SHT3x_LSS_V0.94.pdf
Quoted from page 8:
"Heater: An on chip heating element can be addressed
by writing a command into status register. The heater
may increase the temperature of the sensor by 5 – 10°C8
beyond ambient temperature. The heater draws roughly
25 mW @ 5V supply voltage.
For example the heater can be helpful for functionality
analysis: Humidity and temperature readings before and
after applying the heater are compared. Temperature
shall increase while relative humidity decreases at the
same time. Dew point shall remain the same."
[red emphasis mine]
Anybody know if DAVIS utilize this function within the ISS?
I was considering making some kind of "electronic wet/dry bulb" setup, and I found that SLOWeather already did it.
In California, dealing with the water source for the wet bulb sock would be better for more of the year than here in northern Michigan. I would have to take it down for winter. (or at least empty it)
Has anyone tried this setup?
It is an old thread but is still a valid and timely idea WRT this SHT-31 subject.
https://www.wxforum.net/index.php?topic=4844.0 (https://www.wxforum.net/index.php?topic=4844.0)
Greg H.
The SHT35 will be out in a pin form later this year. It'd be nice if someone could find a simple way to adapt it to a Davis ISS.
Quoted from page 8:
"Heater: An on chip heating element can be addressed
by writing a command into status register. The heater
may increase the temperature of the sensor by 5 – 10°C8
beyond ambient temperature. The heater draws roughly
25 mW @ 5V supply voltage.
For example the heater can be helpful for functionality
analysis: Humidity and temperature readings before and
after applying the heater are compared. Temperature
shall increase while relative humidity decreases at the
same time. Dew point shall remain the same."
[red emphasis mine]
Anybody know if DAVIS utilize this function within the ISS?
As noted in my posts in that thread, it's certainly doable. However, as also noted, using Davis wireless stations on a VP2 console limits you to whole degrees, which I found to be too constraining.
For instance...
Dry Wet RH at 1013 mb
70 60 55.5
71 60 52.1
70 61 59.5
69 60 58.9
Find a way to run matched sensors with at least 0.1° resolution, and it would work.
Here's an equation for it that leaves out BP:
(http://www.1728.org/relhum.png)
In another thread here I proposed building a chilled mirror dew point detector from an Arduino, Peltier device and a stainless steel camping mirror, but have yet to attempt it.I was considering making some kind of "electronic wet/dry bulb" setup, and I found that SLOWeather already did it.
In California, dealing with the water source for the wet bulb sock would be better for more of the year than here in northern Michigan. I would have to take it down for winter. (or at least empty it)
Has anyone tried this setup?
It is an old thread but is still a valid and timely idea WRT this SHT-31 subject.
https://www.wxforum.net/index.php?topic=4844.0 (https://www.wxforum.net/index.php?topic=4844.0)
Greg H.
Do we know if the ISS applies the two correction values for humidity non-linearity and temperature compensation?
I just double checked and I am getting temperatures to 0.1°F increments using meteobridge and meteohub. This might be a workaround for the Davis console integer degrees issue.
Good, in the ISS or the console?Quote
Do we know if the ISS applies the two correction values for humidity non-linearity and temperature compensation?
It does......
Well the sun came out and the wind has been1 to 5 mph a really good test for my dfars test and i am surprised so far that the dfars has been running cooler than both 24 hr fars readings by as much as .5f to 1.0f. I am shocked that so far the high volume fan is working well and if it keeps going like this then it will be really interesting tonight when i turn off the fan an use it as a regular shield and if it works out then that might solve the humidity problem at night. Stay tuned for further updates :grin:Get one of those "daylight/nitelight" sensors to automatically shut off fan at dusk and then turn it back on at dawn?
Quote
Do we know if the ISS applies the two correction values for humidity non-linearity and temperature compensation?
It does......
Good, in the ISS or the console?
Nice post, CW7491! This is why the thread exists - so people can share their experiences and knowledge.
Couple questions:
1) How do you mount the 75 to the shield if you don't use glue or silicon?
2) Approximately how long did your previous 75s last before they went off the rails?
That's good news hope it proves out in the long term. =D>
I've been thinking and have an idea, (which I know is going against proper placement of sensors), but how about raising your ISS higher away from the ground? As I recall, when I had my 5n1, (which uses sensiron) higher at like 25 feet, it read lower on humidity. Would raising the station to say 15 feet help possibly? Just a thought... ? Or try placing the sensor near pavement? (crazy I know for temp)
I've been thinking and have an idea, (which I know is going against proper placement of sensors), but how about raising your ISS higher away from the ground? As I recall, when I had my 5n1, (which uses sensiron) higher at like 25 feet, it read lower on humidity. Would raising the station to say 15 feet help possibly? Just a thought... ? Or try placing the sensor near pavement? (crazy I know for temp)
Think you are right especially those over lawns. I've had so much rain still haven't watered except early spring 1 time after weed and feed. I do believe some moisture is always on grass because you see dew until about 1 pm many days. Only mow late afternoons or grass gets stuck under carriage and plugs becoming pia to clean out.
Somebody Is Lying to me :evil: And there initials are M.A.D.I.S.All CQ's are done by comparing yourself to neighboring stations, be they good or be they bad. All you can do is what you've done, use common sense and understand your data.
Oh and MADIS ?...I'm not re-calibrating anything so you can shove it. \:D/
Somebody Is Lying to me :evil: And there initials are M.A.D.I.S.All CQ's are done by comparing yourself to neighboring stations, be they good or be they bad. All you can do is what you've done, use common sense and understand your data.
Oh and MADIS ?...I'm not re-calibrating anything so you can shove it. \:D/
No one knows your PWS better than you.
I want to preface this by saying, I have only read the first half of this thread (~14 pages or so). So if my account is no longer germane, then sorry. :-P
I have a Davis VP2. Iv'e been getting errors on Dew point from MADIS since I switched to a fan aspirated SHT31 sensor. This particular sensor is only a week old. This and my last SHT31 sensor has shown RH of +8 and Dewpoint of +3-4 degrees according to MADIS and it concerned me.
I live in Louisiana and RH is HIGH as most know. Also, Local airports are showing the same or higher dew points & RH than me almost daily. I've read many people here have little regard for the MADIS ratings and I'll address that too.
I found this thread and decided ..enough is enough!
So today I grabbed 2 Bacharach sling psychs from work. One is a Mercury and about 10 years old (maybe used twice) the other is red spirit and is brand new. Both wet & dry bulb match exactly when dry on both psychrometers.
At test, console shows 39%RH and 66 deg dew point. Temp 95 degrees. It's rather dry here today (Rare) due to a deep trough in the Gulf. Winds have been out of the NNE since yesterday (again, Very rare for July) so measuring mid-range humidity was just lucky timing.
First sling (Mercury) Psych showed 95 Dry and 76 wet worked out to 68 Deg DP , 41.5% RH.
Second (Spirit) showed 93 Dry and 74 Wet worked out to 65 Deg DP 40% RH.
This was done several times as the Temp dropped, and the readings were consistent.
Somebody Is Lying to me :evil: And there initials are M.A.D.I.S.
If anything, I'm reading a bit dry. So, so far, I trust my station's data. I live in a heavily forested rural area with a Lake 2 miles west of me. I'm satisfied that my reading are correct. Oh and MADIS ?...I'm not re-calibrating anything so you can shove it. \:D/
The vast amount of information here on this humidity bias and temp/humidity sensors in general is stunning. Most here have forgotten more than I'll ever learn about all this. Iv'e learned a lot and hope to learn more. Keep up the great discussions everyone.
Ha! Get in an unfortunate line....I guess what got lost in my post (my fault) was that this thread was exacerbating my doubts that 'maybe my sensors are wrong'.Somebody Is Lying to me :evil: And there initials are M.A.D.I.S.All CQ's are done by comparing yourself to neighboring stations, be they good or be they bad. All you can do is what you've done, use common sense and understand your data.
Oh and MADIS ?...I'm not re-calibrating anything so you can shove it. \:D/
No one knows your PWS better than you.
All I can say this is abnormal. I would like to look into it further what CWOP station and airport do you compare to?
Thanks for the location...Really not interested in MADAS but looking at your nearby airport Dewpoint is running about 4° higher. Which is the norm with these sensors.
Can't say anything about the sling readings you got, but they are notorious for giving different readings for different individuals. #1 reason for erratic results was finding appropriate shade. Back in the day ERT training we broke several units with 25 firefighters slinging up next to pumper truck where the only shade was. :lol:
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KAEX
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=D5212&unit=0&timetype=LOCAL
I can't say anything other than it does appear you are wetter.
Could be you have a good sensor and local geography makes it wetter.
I've just never seen it out of 8 different 31's they all act the same with exception some hit 100% others only 96%.
I'm on my 3rd and final batch of baking 31's for reconditioning but out of the sensors I've tested the wet bias is still present.
I purchased all my sensors after the fact (not with station) could very well be there's a bad batch.
It's good you posted results, gives hope just maybe not all are bad and those complaining just have a bad batch.
Bobvelle where did you purchase the new 31?
Bobvelle where did you purchase the new 31?
The latest and the older one both came from Ryan at Scaled Instruments. The newest is the 25ft cabled version though. Which I doubt makes any difference.
I can't say anything other than it does appear you are wetter.
Could be you have a good sensor and local geography makes it wetter.
I've just never seen it out of 8 different 31's they all act the same with exception some hit 100% others only 96%.
I'm on my 3rd and final batch of baking 31's for reconditioning but out of the sensors I've tested the wet bias is still present.
I purchased all my sensors after the fact (not with station) could very well be there's a bad batch.
It's good you posted results, gives hope just maybe not all are bad and those complaining just have a bad batch.
Understood. The first 31 I had, about 2 years now, read 100% on only 2 or 3 occasions. The first time It happened, It was the first foggy night and I was watching it like a hawk. It took about 6 or 8 hours to go from 99% to 100% but it finally did hit it. This one is only a week old and conditions haven't been humid enough yet.
Edit to add: Now that I think about it, it was a passive shield setup at that time too. Nothing inferred with that just full disclosure. And also, on those 2 or 3 occasions it was early in its life. Haven't seen that in a while.
I have followed this forum for years, but never registered or even really considered posting. I have learned a great deal from following all of your comments and experiences over the years. So let me start by saying thank you. This particular topic, however, has brought me out of the shadows …
I have owned Davis equipment since 2005. I bought a VP2. In 2006, I moved to south Texas and upgraded to a 24hr FARS and this is where my frustration with the dew point readings of the VP2 began. My new sensor would never hit 100% humidity and the rest of the scale had a wet bias, but my VP2 from 2005 never had these issues. My 2006 VP2 with FARS had an SHT11 and my 2005 had the old "analog" sensor.
I am no expert obviously, just another guy with a borderline unhealthy obsession with this stuff, but bottom line: my opinion and experience strongly supports that despite the inherent limitation of the Sensirion sensors, there is something about Davis' manufacturing process that causes an offset toward a wet bias.
I have been obsessed with trying to fix and find the source of this bias as well as trying to find a sensor that consistently hits 100% RH. The SHT11 had these issues and disappointingly so did the SHT31. I have moved around a bunch, so I have tested these things from anywhere from Texas to Maine to DC and to the Pacific Northwest. The result has always been the same. I have spent hours over the years with my sensors within 10 feet from the HO-1088 and DTS1 of an ASOS. I have purchased a psychro-dyne for quality checking. I have had the sensors in the -20sF in Maine and Vermont and over 100F in DC and Texas. Here are the main points of what I have learned:
-Outgassing of silicon and glue offsets the Sensirion sensor. The offset seems irreversible. Silicon offsets to the high side. Some glues to the low side. (I discovered this trying to use Sensirion's own filters instead of Davis' filter.)
-The Davis filter may increase response time, but is not responsible for the wet bias.
-The Sensirion sensors do seem to have a slight wet bias as has been documented in some studies, but this wet bias is some how exacerbated by how Davis mounts the sensor.
-The wet bias for Sensirion sensors in prolonged periods near saturation as mentioned in their datasheet is a separate issue from the wet bias created by the Davis mounting.
-The SHT75 straight from the manufacturer without any filter is superior to the Davis mounted SHT31 in terms of dew point and humidity.
-The SHT75 will hit up to 99%, with random very short lived jumps to 100%.
-I miss the old analog sensor
I currently run my station with an SHT75 with no filter at all. I've been doing it for about 6mos. The first 5 of those months were in a stock Davis 24hr FARS. Now it is in the Davis 7714, which is a surprisingly good passive shield (much better than the VP2 stock passive shield) (sometimes a degree or two cooler than the FARS, sometimes a degree or two warmer, at least in the north latitudes of the Seattle area...) I am concerned with contamination and dust, but after trying to put a filter on it with silicon and other glues, I have ruined a fair number of SHT75s with seemingly irreversible offsets. So far I have not seen any evidence of poor performance for lack of a filter.
I run a calibration in Cumulus for the SHT75 (1.041x-3) and field check it with the psychro-dyne. It generally is very close. The psychro-dyne is surprisingly accurate compared side by side to ASOS. I set Cumulus to report 98% as 100% and the calibration I set ensures 99% is reported as 100% too.
This is the best I have been able to do given the limitations of these sensors. I really hope the efforts here will force Davis to look at their process as I'd be happy to have an accurate Davis stock sensor that is engineered to last.
Hope this helps...
I have followed this forum for years, but never registered or even really considered posting. I have learned a great deal from following all of your comments and experiences over the years. So let me start by saying thank you. This particular topic, however, has brought me out of the shadows …
I have owned Davis equipment since 2005. I bought a VP2. In 2006, I moved to south Texas and upgraded to a 24hr FARS and this is where my frustration with the dew point readings of the VP2 began. My new sensor would never hit 100% humidity and the rest of the scale had a wet bias, but my VP2 from 2005 never had these issues. My 2006 VP2 with FARS had an SHT11 and my 2005 had the old "analog" sensor.
I am no expert obviously, just another guy with a borderline unhealthy obsession with this stuff, but bottom line: my opinion and experience strongly supports that despite the inherent limitation of the Sensirion sensors, there is something about Davis' manufacturing process that causes an offset toward a wet bias.
I have been obsessed with trying to fix and find the source of this bias as well as trying to find a sensor that consistently hits 100% RH. The SHT11 had these issues and disappointingly so did the SHT31. I have moved around a bunch, so I have tested these things from anywhere from Texas to Maine to DC and to the Pacific Northwest. The result has always been the same. I have spent hours over the years with my sensors within 10 feet from the HO-1088 and DTS1 of an ASOS. I have purchased a psychro-dyne for quality checking. I have had the sensors in the -20sF in Maine and Vermont and over 100F in DC and Texas. Here are the main points of what I have learned:
-Outgassing of silicon and glue offsets the Sensirion sensor. The offset seems irreversible. Silicon offsets to the high side. Some glues to the low side. (I discovered this trying to use Sensirion's own filters instead of Davis' filter.)
-The Davis filter may increase response time, but is not responsible for the wet bias.
-The Sensirion sensors do seem to have a slight wet bias as has been documented in some studies, but this wet bias is some how exacerbated by how Davis mounts the sensor.
-The wet bias for Sensirion sensors in prolonged periods near saturation as mentioned in their datasheet is a separate issue from the wet bias created by the Davis mounting.
-The SHT75 straight from the manufacturer without any filter is superior to the Davis mounted SHT31 in terms of dew point and humidity.
-The SHT75 will hit up to 99%, with random very short lived jumps to 100%.
-I miss the old analog sensor
I currently run my station with an SHT75 with no filter at all. I've been doing it for about 6mos. The first 5 of those months were in a stock Davis 24hr FARS. Now it is in the Davis 7714, which is a surprisingly good passive shield (much better than the VP2 stock passive shield) (sometimes a degree or two cooler than the FARS, sometimes a degree or two warmer, at least in the north latitudes of the Seattle area...) I am concerned with contamination and dust, but after trying to put a filter on it with silicon and other glues, I have ruined a fair number of SHT75s with seemingly irreversible offsets. So far I have not seen any evidence of poor performance for lack of a filter.
I run a calibration in Cumulus for the SHT75 (1.041x-3) and field check it with the psychro-dyne. It generally is very close. The psychro-dyne is surprisingly accurate compared side by side to ASOS. I set Cumulus to report 98% as 100% and the calibration I set ensures 99% is reported as 100% too.
This is the best I have been able to do given the limitations of these sensors. I really hope the efforts here will force Davis to look at their process as I'd be happy to have an accurate Davis stock sensor that is engineered to last.
Hope this helps...
I can say I've always been told the Davis 7714 was a good passive shield and yes it blows the VP2 stock passive shield away. I just installed one today mid July at 43° near South Dakota border and running a full degree below both FARS shields and this is with very light winds.
This is over cut grass and 75-80F range currently with very high sun angle (straight up) July. Whether this changes once the sun is low will wait and see this winter.
I'll never say a passive shield shouldn't be used again after testing this unit. I did paint the inside bottom where sensor mounts and top inside flat black because I can never keep anything fully stock. It's just an issue I have. :oops:
All the solar radiation 'reflection' plates in our YPG tank-testing ambient air thermal-couple sensors had WHITE tops and flat-BLACK bottoms.
I can say I've always been told the Davis 7714 was a good passive shield and yes it blows the VP2 stock passive shield away. I just installed one today mid July at 43° near South Dakota border and running a full degree below both FARS shields and this is with very light winds.
This is over cut grass and 75-80F range currently with very high sun angle (straight up) July. Whether this changes once the sun is low will wait and see this winter.
I'll never say a passive shield shouldn't be used again after testing this unit. I did paint the inside bottom where sensor mounts and top inside flat black because I can never keep anything fully stock. It's just an issue I have. :oops:
The SRS100LX has 9 plates spaced over 10.75-inches. That's a little over 1-inch spacing between each plate and the plate "lips" are deeper than each plate-to-plate spacing, so there's LOTS of air flow capability. Years ago I used one with my LaCrosse WS-8610U system once I figured out that their crappy unit was totally worthless.I can say I've always been told the Davis 7714 was a good passive shield and yes it blows the VP2 stock passive shield away. I just installed one today mid July at 43° near South Dakota border and running a full degree below both FARS shields and this is with very light winds.
This is over cut grass and 75-80F range currently with very high sun angle (straight up) July. Whether this changes once the sun is low will wait and see this winter.
I'll never say a passive shield shouldn't be used again after testing this unit. I did paint the inside bottom where sensor mounts and top inside flat black because I can never keep anything fully stock. It's just an issue I have. :oops:
Questions & observations.
First, you couldn't get a more basic "Gill" type shield. Ambient Weather has their own version (SRS100LX).
What did Davis do so wrong with their stock passive shield that it can't beat something that looks like it was designed and constructed in 8th grade science class?
Did you mount an SHTxx sensor in there? If so, how?
You recently modified the FARS shield to make it passive. You said it had amazing performance. How's it holding up?
The SRS100LX has 9 plates spaced over 10.75-inches. That's a little over 1-inch spacing between each plate and the plate "lips" are deeper than each plate-to-plate spacing, so there's LOTS of air flow capability. Years ago I used one with my LaCrosse WS-8610U system once I figured out that their crappy unit was totally worthless.
The SRS100LX has 9 plates spaced over 10.75-inches. That's a little over 1-inch spacing between each plate and the plate "lips" are deeper than each plate-to-plate spacing, so there's LOTS of air flow capability. Years ago I used one with my LaCrosse WS-8610U system once I figured out that their crappy unit was totally worthless.
The problem out this way with more spacing is it makes it easier for wind-driven snow to get in and sit on the sensor.
I can say I've always been told the Davis 7714 was a good passive shield and yes it blows the VP2 stock passive shield away. I just installed one today mid July at 43° near South Dakota border and running a full degree below both FARS shields and this is with very light winds.
This is over cut grass and 75-80F range currently with very high sun angle (straight up) July. Whether this changes once the sun is low will wait and see this winter.
I'll never say a passive shield shouldn't be used again after testing this unit. I did paint the inside bottom where sensor mounts and top inside flat black because I can never keep anything fully stock. It's just an issue I have. :oops:
Questions & observations.
First, you couldn't get a more basic "Gill" type shield. Ambient Weather has their own version (SRS100LX).
What did Davis do so wrong with their stock passive shield that it can't beat something that looks like it was designed and constructed in 8th grade science class? I tested the VP2 stock couple years ago and was running very warm +3 at times.
Did you mount an SHTxx sensor in there? If so, how? Yes, same place designed for a metal probe in middle but just used 1 screw and not bracket for metal probe
You recently modified the FARS shield to make it passive. You said it had amazing performance. How's it holding up? It did really well until it got calm and then was running +2°. Still better than the stock VP2 I would say.
What did Davis do so wrong with their stock passive shield that it can't beat something that looks like it was designed and constructed in 8th grade science class? I tested the VP2 stock couple years ago and was running very warm +3 at times.
Thanks for the info!Many folks are under the impression that a FARS only benefits hot climates. I got to the point where I quit trying. ](*,)What did Davis do so wrong with their stock passive shield that it can't beat something that looks like it was designed and constructed in 8th grade science class? I tested the VP2 stock couple years ago and was running very warm +3 at times.I've seen worse over fresh snow (6F+ compared to my FARS).
I personally think the Davis stock shield does well. There is lagging but as along as you sited over grass and have a nice breeze on a consistent basis, it does good.Problem is, you can control the siting, not the breeze, especially on a consistent basis.
I personally think the Davis stock shield does well. There is lagging but as along as you sited over grass and have a nice breeze on a consistent basis, it does good.Problem is, you can control the siting, not the breeze, especially on a consistent basis.
I ordered a Davis DFARS "kit" and will DIY'ing it to be my "secondary/back-up" TEMP/RH system using an "old" spare ISS I have. Plan is for easy (hopefully) sensor access/change-out; it'll be mounted on same pole as current VP2, only pointing North so as NOT to physically interfere with the VP2. Should enable me to simultaneously test/play with older SHT-15 and current SHT-31 sensors (old & new) that I have stock-piled.
No more FARS for me if these 7714's work out. I really hope we get some hot weather before slipping into fall. Seems like all of a sudden only 70-80 & no 90's in sight so hard to confirm what I'm seeing. For sure I'll continue side by side test even into winter. Once the grass has turned and all leaves are gone, with different sun angles results could differ but very encouraging now in my heavy foliage humid environment.
No more FARS for me if these 7714's work out. I really hope we get some hot weather before slipping into fall. Seems like all of a sudden only 70-80 & no 90's in sight so hard to confirm what I'm seeing. For sure I'll continue side by side test even into winter. Once the grass has turned and all leaves are gone, with different sun angles results could differ but very encouraging now in my heavy foliage humid environment.
No way I'm giving up FARS. Even though I 'm frustrated to no end over the wet bias, the temperature is spot on. I will just have to wait for Davis to come up with a solution to the humidity issues we've all been experiencing.
Thanks for the link. I didn't mean to stray from the topic. I personally don't believe the FARS is the culprit here. My personal feeling is the 31 sensor is the problem, not temperature, just humidity.
In my best Cuba Gooding, Jr imitation voice, "...ShowYou had my data at hello.meUS themoneyDATA..." (ha,ha)!
I've been dealing with a stomach bug and a cold turkey, coffee quitting, caffeine withdrawal migraine so my new toys aren't getting installed until this weekend. I got a couple of new 12V FARS fans, new rad plates, aerocone, new uv/solar covers, new SHT75, and new connectors to make the 12 y/o VP2 look somewhat new again. I'll post some graphs later Sunday if I can get everything installed Saturday morning (or tonight if I'm up for it). I'll be able to show you the difference in my response times between the SHT31 (no cover) and SHT75 (no cover) with the same 40 CFM fan. We'll see how high the new 75's RH can reach too.
Would I be correct to say that the SHT-75 doesn’t have the wet bias like the SHT-31? Because I don’t see it with the comparison with these two stations...I don't have the 75 in right now...that's the uncovered 31 with the 40CFM fan. LCI is an AWOS and I'm not sure what they're using for dewpoint sensing right now. Maybe someone else here knows if it's the Vaisala PTU307 or something else. CON is about 20 miles south of me and that's an ASOS.
https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=KLCI&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
SHT-75. https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=C7324&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
Would I be correct to say that the SHT-75 doesn’t have the wet bias like the SHT-31? Because I don’t see it with the comparison with these two stations...
https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=KLCI&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
SHT-75. https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=C7324&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
I wouldn’t compare my station to LCI. They’re on the water and I’m on a hill. There’s a lot of terrain effects out here so I gave up comparing to other stations.Would I be correct to say that the SHT-75 doesn’t have the wet bias like the SHT-31? Because I don’t see it with the comparison with these two stations...
https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=KLCI&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
SHT-75. https://mesowest.utah.edu/cgi-bin/droman/meso_table_mesowest_m.cgi?stn=C7324&unit=0&time=&hours=24&hour1=23&day1=26&month1=07&year1=2018&radius=25&past=0&order=1
Ambient temperature is so different 6°, I hesitate to compare. Even DP will fluctuate some with temperature I've noticed and C7324 is 2° higher with ambient 6° lower so I think the wet bias is still there.
I have the 75 almost ready to go. Here it is next to a Davis sensor for size comparison.
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Ran a little experiment over night and today, i put a sensor in a damp wash cloth an let it sit over night showing 98%. This am i removed it from the cloth and put it in a fars to see how it would respond, well it was running around 2% high to start and as the day went on the humidity on main station was running around 39 to 45% but the test sensor was running between 5 to 7% higher. So i removed the sensor and baked it for several hours and the error corrected itself and after awhile was checking with the other station. So what they say about prolonged exposure to high humidity sure showed up and with a fan running at night in high humidity you can image the error that shows up until it dries out. One thing it does correct itself but it takes awhile and your reported readings are going to be really screwed up for awhile. I had noticed for a long time that the humidity reading was slow to come down in the am after a humid night, sometimes taking two to three hours to get dried out.
Ran a little experiment over night and today, i put a sensor in a damp wash cloth an let it sit over night showing 98%. This am i removed it from the cloth and put it in a fars to see how it would respond, well it was running around 2% high to start and as the day went on the humidity on main station was running around 39 to 45% but the test sensor was running between 5 to 7% higher. So i removed the sensor and baked it for several hours and the error corrected itself and after awhile was checking with the other station. So what they say about prolonged exposure to high humidity sure showed up and with a fan running at night in high humidity you can image the error that shows up until it dries out. One thing it does correct itself but it takes awhile and your reported readings are going to be really screwed up for awhile. I had noticed for a long time that the humidity reading was slow to come down in the am after a humid night, sometimes taking two to three hours to get dried out.
So what they say about prolonged exposure to high humidity sure showed up and with a fan running at night in high humidity you can image the error that shows up until it dries out.I'm still trying to wrap my head around how a fan could possibly keep a sensor "wetter" than a passive shield. Evaporation or saturation is merely expedited by the fan, how could that not be desirable??
I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air.I don't see it. All a fan does is take ambient air and draw it across the sensor, evaporating or saturating certainly more efficient than any passive shield.
Which exposed wires? I have some silicone conformal coating I may put on the pin end of the 75 PCB and up to where it meets the connector. Maybe I'll put a little on the wire end of the connector too.I have the 75 almost ready to go. Here it is next to a Davis sensor for size comparison.
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Oh wow! You didn’t have to solder right? How are you going to protect the exposed wires?
I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air.I don't see it. All a fan does is take ambient air and draw it across the sensor, evaporating or saturating certainly more efficient than any passive shield.
Not saying your observations are wrong, but my physics don't see your physics. :???:
I used an 11 that i have and i don't know why things work the way they do i just know in a side by side comparison the fars takes longer to dry out than the standard shield. I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air. I took a fars apart early in the am while still high humidity and the inside of the sensor chamber was really damp with beads of moisture and it takes awhile for the fan to pull enough dry air through the chambers and tubes to dry everything out so no false readings by the sensor. Just my thoughts on the matter, i am no expert on this stuff but i believe what i see with my own eyes.
I would certainly think the small area in the chamber would negate sensor placement. The filter also keeps the "full force" of the air off the sensor.but its seems to me that being in that area actually keeps the full force of the air from blowing directly on the sensor, while at the same time still 'saturated' in the air pulled in from below.I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air.I don't see it. All a fan does is take ambient air and draw it across the sensor, evaporating or saturating certainly more efficient than any passive shield.
Not saying your observations are wrong, but my physics don't see your physics. :???:
Which exposed wires? I have some silicone conformal coating I may put on the pin end of the 75 PCB and up to where it meets the connector. Maybe I'll put a little on the wire end of the connector too.I have the 75 almost ready to go. Here it is next to a Davis sensor for size comparison.
[ You are not allowed to view attachments ]
Oh wow! You didn’t have to solder right? How are you going to protect the exposed wires?
And no, no soldering. It's an IDC connector so slide the wires in all the way and close it up tight. I think the Davis wires are 26 AWG and the connector accepts 26-28 AWG.
Good deal. Will probably end up doing that.
I would certainly think the small area in the chamber would negate sensor placement. The filter also keeps the "full force" of the air off the sensor.but its seems to me that being in that area actually keeps the full force of the air from blowing directly on the sensor, while at the same time still 'saturated' in the air pulled in from below.I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air.I don't see it. All a fan does is take ambient air and draw it across the sensor, evaporating or saturating certainly more efficient than any passive shield.
Not saying your observations are wrong, but my physics don't see your physics. :???:
You put the sensor where you believe is the most beneficial. That being said, I think you're waaay over thinking this. Whether the sensor receives more or less of a laminar flow is irrelevant.I would certainly think the small area in the chamber would negate sensor placement. The filter also keeps the "full force" of the air off the sensor.but its seems to me that being in that area actually keeps the full force of the air from blowing directly on the sensor, while at the same time still 'saturated' in the air pulled in from below.I think the fars with the big chamber it has has a lot more area to retain condensed moisture than the standard shield with the sensor located at the bottom so is more readily exposed to the drier air with all the plates being open to the air.I don't see it. All a fan does is take ambient air and draw it across the sensor, evaporating or saturating certainly more efficient than any passive shield.
Not saying your observations are wrong, but my physics don't see your physics. :???:
I disagree. The baffle at the bottom of the chamber produces a small area semi-stagnate air. The sensor can be placed near this area. Above that small area is a turbulence zone ...and near the top by the fan, faster and straighter moving air. Plenty of room for all that to take place.
Also, there would be no sense in adding the SF2 Sensirion filter cap if the air is not directly hitting the sensor. According to you, the cap will block this air.
By the way, my choice of the term 'full force of air' was hyperbole. We all know there is no 'force' when air is being drawn through the chamber with the typical fan.
Yeah. I may add the silicone conformal coating around those holes where the wires enter to make sure no moisture finds its way in. With this connector I didn't even have to strip the wires...just a clean straight cut across. When you close the connector it slices into the wire to make the insulated connection, but better to be safe than sorry when it comes to moisture.Which exposed wires? I have some silicone conformal coating I may put on the pin end of the 75 PCB and up to where it meets the connector. Maybe I'll put a little on the wire end of the connector too.I have the 75 almost ready to go. Here it is next to a Davis sensor for size comparison.
[ You are not allowed to view attachments ]
Oh wow! You didn’t have to solder right? How are you going to protect the exposed wires?
And no, no soldering. It's an IDC connector so slide the wires in all the way and close it up tight. I think the Davis wires are 26 AWG and the connector accepts 26-28 AWG.
Good deal. Will probably end up doing that.
Between where you spliced the wires and the connector.
However, based on what we are seeing across the board, we recommend client configurations of temperature sensor in FARS and humidity sensor in an open passive shield (non-gill plate) to maintain optimum performance and calibration.
However, based on what we are seeing across the board, we recommend client configurations of temperature sensor in FARS and humidity sensor in an open passive shield (non-gill plate) to maintain optimum performance and calibration.
What is "an open passive shield (non-gill plate)"? What would that look like? Just a Bell or Cone shaped shelter?
However, based on what we are seeing across the board, we recommend client configurations of temperature sensor in FARS and humidity sensor in an open passive shield (non-gill plate) to maintain optimum performance and calibration.
What is "an open passive shield (non-gill plate)"? What would that look like? Just a Bell or Cone shaped shelter?
Image near top of thread Kcidwx posted of the ASOS sensor was open shield. Basically has a umbrella and fully exposed underneath.
So then I get asked, "What should I do since I have a combined temperature and humidity sensor?" I say put it in a FARS for temperature accuracy and hope your humidity sensor holds up. If not, replace the sensor. If you don't have the means to properly test the humidity side of the sensor and you are concerned about its accuracy long term, just get on a schedule to replace it every 12 to 18 months.
My last Acurite check early this morning max humidity at 97%, Davis 96% aspirated so both looking normal.
At 12:40 CT I did a passive shade check against new Davis sensor with 5mph breeze running 7-9% lower humidity so really nothing changed from yesterday.
Not keeping acurite saturated in high humidity outside 24/7 so can't really determine how much drift if any is taking place toward wet side. Max exposure time has been around 2 hours in early morning allowing it to record highest humidity.
Im guessing you’re like me. DPs are 3-4 degrees off being wet in bias
+4° dp when I did the afternoon check. Thread has gone about as far as it can go unless anyone has something we didn't cover. Let Davis do their thing and see what they come up with.
My last Acurite check early this morning max humidity at 97%, Davis 96% aspirated so both looking normal.
At 12:40 CT I did a passive shade check against new Davis sensor with 5mph breeze running 7-9% lower humidity so really nothing changed from yesterday.
Not keeping acurite saturated in high humidity outside 24/7 so can't really determine how much drift if any is taking place toward wet side. Max exposure time has been around 2 hours in early morning allowing it to record highest humidity.
Im guessing you’re like me. DPs are 3-4 degrees off being wet in bias
+4° dp when I did the afternoon check. Thread has gone about as far as it can go unless anyone has something we didn't cover. Let Davis do their thing and see what they come up with.
This quote is from post 475 and we thought we were done until Davis replied! Has Davis done its thing yet? I certainly haven’t heard anything and I doubt anyone else has including the resellers of the world, like Johnd and Ryan Wilhour.
This quote is from post 475 and we thought we were done until Davis replied! Has Davis done its thing yet? I certainly haven’t heard anything and I doubt anyone else has including the resellers of the world, like Johnd and Ryan Wilhour.
So then I get asked, "What should I do since I have a combined temperature and humidity sensor?" I say put it in a FARS for temperature accuracy and hope your humidity sensor holds up. If not, replace the sensor. If you don't have the means to properly test the humidity side of the sensor and you are concerned about its accuracy long term, just get on a schedule to replace it every 12 to 18 months.
OK fair enough, Ron.
But when the official parts suppliers only carry sensors with wet biases "preinstalled", what then? Davis had BETTER be working on a solution.
After a couple of PM's on this, let me address the issue of "best practice". So where does the best practice come from about not aspirating humidity sensors. It comes from us field techs. It's frustrating when I tell people in a PM what we are seeing in the field and they come back with, "but the sensor manufacturer says this" or "the manufacturers document says that". I like to use the car analogy here. Who would you trust more in getting information about minor problems being experienced with a particular type of GM car? GM or the local independent mechanic that works on their cars everyday? Us meteorological field techs are the independent mechanics.
Just like the wet bias I discovered over a year ago with the SHT-31. Did Davis know about it? Nope! A year later someone on this forum finally told them about it. My test proved that the field techs are aware of many sensor issues that the manufacturers aren't. Not everything gets back to the manufacturers and even if it does they may not think it's a big enough problem to do anything about it. From our experiences, we develop our own best practices when it comes to sensors.
So now back to the humidity sensor best practice and where it comes from. We recycle humidity sensors on average every 18 months. We lab test the sensors when they are new right before they are put in service. They are also spot checked right after being put in service and tested in more detail every 90 days thereafter. That test data gets logged by sensor serial number. That sensor is spot checked again at the 18 month recycle time before it is pulled out of service. We lab test it again right after it is pulled out of service. What we are seeing is that we have a much higher number of sensors that we pull out of FARS installations that are right on the edge of the spec or are already slightly out of spec versus those we pull out of passive shields. Unfortunately none of us field techs has taken the time to try and fully understand why this is happening. Those nearly out of spec or out of spec sensors all show a wet bias. They often fail other sensor metrics we test as well. Getting to travel all over the country to work on different installations, it's a much bigger problem in humid regions.
Again this is not happening to ALL humidity sensors in a FARS. We pull many humidity sensors that show no ill effects after 18 months of being in a FARS. However, based on what we are seeing across the board, we recommend client configurations of temperature sensor in FARS and humidity sensor in an open passive shield (non-gill plate) to maintain optimum performance and calibration. FARS is great for humidity response time and a few other positives but what good is that if we check the sensor during the 18 month in service period and it's out of spec or fails one of the other metrics we test.
Just an FYI, I don't do any work with Davis sensors. My SHT-31 tests I did were done on the side and for my own curiosity.
So then I get asked, "What should I do since I have a combined temperature and humidity sensor?" I say put it in a FARS for temperature accuracy and hope your humidity sensor holds up. If not, replace the sensor. If you don't have the means to properly test the humidity side of the sensor and you are concerned about its accuracy long term, just get on a schedule to replace it every 12 to 18 months.
Again, for the record, I'm not saying the FARS is causing the problem with the Davis sensors in any way shape or form. It's just one possibility that needs to be investigated.
This reported issue doesn't sound like something that can be validated, fixed and tested quickly, even assuming that any fix is possible. Add into the mix that Davis are, I suspect, very busy with other priorities right now and this issue might have to take its place in the queue (at least beyond that some bland statement that Davis are looking into the report and maybe some updated maintenance advice).
The reality could - but only could, I emphasise - be that users needing real accuracy and long-term stability in RH readings should consider buying eg a Vaisala station (and a suitable maintenance contract).
If that's the case then you are at the mercy of the vendor. However, I would not expect a quick response from them if you even get a response at all. They will need to do a lot of troubleshooting and testing to determine the cause. That can take months, even years depending on the nature and complexity of the problem. Even then the most probable cost effective solution (if this is a widespread problem) would be for Davis to publish their own set of specs for their PCB mounted SHT-31. Not uncommon for vendors to do that. The new Davis specs might look something like this.
Temperature (-40°F to +194°F) (0 - 90 %RH) 2.0 %RH
(90 - 100 %RH) 3.5 %RH
Temperature (+80°F to +120°F) (40 - 70 %RH) 4.0 %RH
Great stuff guys.
I spent the morning refurbing my VP2...new rad plates, uv/solar covers, aerocone, etc. it almost looks like I just bought it.
Anyway, I put my old SHT75 back in the FARS for now. I put silicone conformal coating on the new one so that’ll take a little time to cure at regular ambient air temps. Maybe tomorrow morning I’ll swap it out with the new one.
C7324 is my station for those who want to follow along. I wouldn’t overanalyze the readings too much until I put the new sensor in. Feel free to critique away then.
So I thought I wanted a VP2 but now I'm not so sure. Maybe I'll wait. I'm just a hobbyists with a cheap Ambient Weather WS-2902A. I think Davis needs to fix this humidity problem and soon not months or years later. Sure things take time to fix but you all have done tremendous work in less than a month. I expect Davis to put this at the top of their priority list. Well maybe just second to releasing a decent successor, the VP3, or whatever they want to call it. The VP3 is way overdue. I implore Davis to design the VP3 with separate temperature and heated humidity sensors. That solution does not break the value / price point mark. And they need to revise their manufacturing/shipping methods to ensure better quality control. But they can't forget about their loyal VP2 customers and offer them a solution too.Davis has been badgered by us (CWOP's) for years and seldom (but not never) responds, rather they listen and then eventually (maybe) responds. Unfortunately "silent" patience is NOT our virtue.
I predict that if Davis doesn't fix this problem soon and also if they don't release a VP3 within a year that there will be another manufacturer that starts to take away their sales. Already the Acurite Atlas has gotten alot of excitement and the Atlas Elite sounds like it might just be a VP2 killer.
I propose we reach out to organizations that use VP2s and let them know what you all have discovered. For example reach out to WeatherSTEM and let them know the VP2 is not all it is cracked up to be. Maybe Davis needs to see pressure from not just this forum. We need to get Davis' big customers to be informed. Anyone know any other big Davis customers?
But not just customers need to know but also resellers. Good that Scaled Instruments knows. How about letting other vendors know? Has anyone let Ed at Ambient Weather know? Or how about Scientific Sales, do they know?
If you all want this problem fixed then let's light a fire and get Davis to respond. I'm talking about getting a real response. Not some canned "we are looking at it" BS statement. They need to quickly acknowledge the issue and promise a solution. Then they need to deliver a few months later but within 6 months.
I'm not all talk. I'll be glad to reach out to whomever. Let's make a list. And let's get our messaging straight. But maybe some of you already are a better inside contact for these organizations.
So I thought I wanted a VP2 but now I'm not so sure. Maybe I'll wait. I'm just a hobbyists with a cheap Ambient Weather WS-2902A. I think Davis needs to fix this humidity problem and soon not months or years later. Sure things take time to fix but you all have done tremendous work in less than a month. I expect Davis to put this at the top of their priority list. Well maybe just second to releasing a decent successor, the VP3, or whatever they want to call it. The VP3 is way overdue. I implore Davis to design the VP3 with separate temperature and heated humidity sensors. That solution does not break the value / price point mark. And they need to revise their manufacturing/shipping methods to ensure better quality control. But they can't forget about their loyal VP2 customers and offer them a solution too.
I predict that if Davis doesn't fix this problem soon and also if they don't release a VP3 within a year that there will be another manufacturer that starts to take away their sales. Already the Acurite Atlas has gotten alot of excitement and the Atlas Elite sounds like it might just be a VP2 killer.
I propose we reach out to organizations that use VP2s and let them know what you all have discovered. For example reach out to WeatherSTEM and let them know the VP2 is not all it is cracked up to be. Maybe Davis needs to see pressure from not just this forum. We need to get Davis' big customers to be informed. Anyone know any other big Davis customers?
But not just customers need to know but also resellers. Good that Scaled Instruments knows. How about letting other vendors know? Has anyone let Ed at Ambient Weather know? Or how about Scientific Sales, do they know?
If you all want this problem fixed then let's light a fire and get Davis to respond. I'm talking about getting a real response. Not some canned "we are looking at it" BS statement. They need to quickly acknowledge the issue and promise a solution. Then they need to deliver a few months later but within 6 months.
I'm not all talk. I'll be glad to reach out to whomever. Let's make a list. And let's get our messaging straight. But maybe some of you already are a better inside contact for these organizations.
So I thought I wanted a VP2 but now I'm not so sure. Maybe I'll wait. I'm just a hobbyists with a cheap Ambient Weather WS-2902A. I think Davis needs to fix this humidity problem and soon not months or years later. Sure things take time to fix but you all have done tremendous work in less than a month. I expect Davis to put this at the top of their priority list. Well maybe just second to releasing a decent successor, the VP3, or whatever they want to call it. The VP3 is way overdue. I implore Davis to design the VP3 with separate temperature and heated humidity sensors. That solution does not break the value / price point mark. And they need to revise their manufacturing/shipping methods to ensure better quality control. But they can't forget about their loyal VP2 customers and offer them a solution too.
I predict that if Davis doesn't fix this problem soon and also if they don't release a VP3 within a year that there will be another manufacturer that starts to take away their sales. Already the Acurite Atlas has gotten alot of excitement and the Atlas Elite sounds like it might just be a VP2 killer.
I propose we reach out to organizations that use VP2s and let them know what you all have discovered. For example reach out to WeatherSTEM and let them know the VP2 is not all it is cracked up to be. Maybe Davis needs to see pressure from not just this forum. We need to get Davis' big customers to be informed. Anyone know any other big Davis customers?
But not just customers need to know but also resellers. Good that Scaled Instruments knows. How about letting other vendors know? Has anyone let Ed at Ambient Weather know? Or how about Scientific Sales, do they know?
If you all want this problem fixed then let's light a fire and get Davis to respond. I'm talking about getting a real response. Not some canned "we are looking at it" BS statement. They need to quickly acknowledge the issue and promise a solution. Then they need to deliver a few months later but within 6 months.
I'm not all talk. I'll be glad to reach out to whomever. Let's make a list. And let's get our messaging straight. But maybe some of you already are a better inside contact for these organizations.
I propose we reach out to organizations that use VP2s and let them know what you all have discovered. For example reach out to WeatherSTEM and let them know the VP2 is not all it is cracked up to be. Maybe Davis needs to see pressure from not just this forum. We need to get Davis' big customers to be informed. Anyone know any other big Davis customers?
But not just customers need to know but also resellers. Good that Scaled Instruments knows. How about letting other vendors know? Has anyone let Ed at Ambient Weather know? Or how about Scientific Sales, do they know?
If you all want this problem fixed then let's light a fire and get Davis to respond. I'm talking about getting a real response. Not some canned "we are looking at it" BS statement. They need to quickly acknowledge the issue and promise a solution. Then they need to deliver a few months later but within 6 months.
I'm not all talk. I'll be glad to reach out to whomever. Let's make a list. And let's get our messaging straight. But maybe some of you already are a better inside contact for these organizations.
I personally think the quick solution is to use the Sensirion mounted 75. Be on the process of redoing the transmitter board; so that it can take the new 35 (that’s replacing the 75) next year. Also, use Sensirion filter cap and not the one they use now.
I personally think the quick solution is to use the Sensirion mounted 75. Be on the process of redoing the transmitter board; so that it can take the new 35 (that’s replacing the 75) next year. Also, use Sensirion filter cap and not the one they use now.
Has it been determined the 75 doesn't have the wet bias?
I could live with it during summer and change to the 31 for winter.
From the side by sides I’ve done, the unmodified 75 runs consistently drier than the Davis-mounted 31 in the midrange as low as humidity in the 20s. (And I stress it is unmodified). That said, it’s not perfect and is still a Sensirion. It struggles to hit 100%, but gets there on occasion. It hits 98 and 99 regularly. It will still exhibit a wet bias if in high humidity for a prolonged period and I’d say it may have a slight wet bias generally, but it compares really closely to my psycho-dyne. I’d love to find a way to get a 31 or 35 that Davis hasn’t touched to work with my VP2, but until then, my experience is having the 75 is markedly superior to the Davis 31. Temp specs are not as good obviously and not exactly a rigorous study, but I’ve tested side by side with an ASOS at -8F and it was right on. Not trying to convince anyone, but just my experience ...
While I want better and more reliable humidity readings, accurate temperature is more important to me, so whatever “bandaid” or work around is developed, it can’t reduce temperature accuracy. Right now the SHT31 is excellent when monitoring temperature. If need be, I will just live with my SHT31 to get the temperature and accept that its humidity readings are just plain flaky. And maybe this perspective is why Davis hasn’t made humidity correction a high priority.
From the side by sides I’ve done, the unmodified 75 runs consistently drier than the Davis-mounted 31 in the midrange as low as humidity in the 20s. (And I stress it is unmodified). That said, it’s not perfect and is still a Sensirion. It struggles to hit 100%, but gets there on occasion. It hits 98 and 99 regularly. It will still exhibit a wet bias if in high humidity for a prolonged period and I’d say it may have a slight wet bias generally, but it compares really closely to my psycho-dyne. I’d love to find a way to get a 31 or 35 that Davis hasn’t touched to work with my VP2, but until then, my experience is having the 75 is markedly superior to the Davis 31. Temp specs are not as good obviously and not exactly a rigorous study, but I’ve tested side by side with an ASOS at -8F and it was right on. Not trying to convince anyone, but just my experience ...
How much of the difference is there between the 75 & psych-dyne?
While I want better and more reliable humidity readings, accurate temperature is more important to me, so whatever “bandaid” or work around is developed, it can’t reduce temperature accuracy. Right now the SHT31 is excellent when monitoring temperature. If need be, I will just live with my SHT31 to get the temperature and accept that its humidity readings are just plain flaky. And maybe this perspective is why Davis hasn’t made humidity correction a high priority.
The temp sensing 'device' in the SHt31 is an electronic PN-junction on silicon(?) wafer and is typically VERY accurate, because PN-junction electron-flow has a very specific rate-to-temperature ratio.
From the side by sides I’ve done, the unmodified 75 runs consistently drier than the Davis-mounted 31 in the midrange as low as humidity in the 20s. (And I stress it is unmodified). That said, it’s not perfect and is still a Sensirion. It struggles to hit 100%, but gets there on occasion. It hits 98 and 99 regularly. It will still exhibit a wet bias if in high humidity for a prolonged period and I’d say it may have a slight wet bias generally, but it compares really closely to my psycho-dyne. I’d love to find a way to get a 31 or 35 that Davis hasn’t touched to work with my VP2, but until then, my experience is having the 75 is markedly superior to the Davis 31. Temp specs are not as good obviously and not exactly a rigorous study, but I’ve tested side by side with an ASOS at -8F and it was right on. Not trying to convince anyone, but just my experience ...
How much of the difference is there between the 75 & psych-dyne?
Usually pretty spot on. Within 1F in dew point. Sometimes 2F. The nice thing about the 75 is you can put it right in the intake of the psychro dyne to verify temp and dew point. I know some others are using the 75 so they may be able to provide more input in terms of temp/hum accuracy of the 75 across the extreme ranges
he has applied over 40,000 hours toward perfecting our weather products and components. We believe that it is one of the many reasons our weather stations have stood the test of time
Precision matters, says Richard. We design our products to the tightest tolerances for consistent manufacturing and assembly, which results in dependable, quality products.
Hey everyone,
It is this guy's fault... Richard Anderson design engineer at Davis. Anyone know how to reach him? Well in all seriousness it probably isn't truly his fault alone. But we have a name at Davis. Maybe he has some answers.
https://www.davisinstruments.com/blog/meet-davis-design-engineer-richard-anderson/
From the link above it says,Quotehe has applied over 40,000 hours toward perfecting our weather products and components. We believe that it is one of the many reasons our weather stations have stood the test of time
Well I think we all have something to say about that.
However, he is just a foot soldier. Contacting him isn't going to move the needle as he will have to get in line behind his superiors.
But if I were him, I wouldn't want my name anywhere near this mess.
I know that his name is on the 1999 patent application for the Davis FARS design. See: https://patents.google.com/patent/US6247360B1/en (https://patents.google.com/patent/US6247360B1/en).
.
As Johnd, our reseller friend from the UK, has noted the demand for PWS is not huge so we don’t have a lot of pent-up demand for a better product so unless the Atlas device takes off, is reliable and well built, we don’t have a lot of choices. Frustrating yes, but....Could be a double-edged sword for Davis. If the market is small, Davis may have a hard time affording the resources necessary for quick research, testing, development, production, and rectifying the problems with the units already sold and produced.
From the side by sides I’ve done, the unmodified 75 runs consistently drier than the Davis-mounted 31 in the midrange as low as humidity in the 20s. (And I stress it is unmodified). That said, it’s not perfect and is still a Sensirion. It struggles to hit 100%, but gets there on occasion. It hits 98 and 99 regularly. It will still exhibit a wet bias if in high humidity for a prolonged period and I’d say it may have a slight wet bias generally, but it compares really closely to my psycho-dyne. I’d love to find a way to get a 31 or 35 that Davis hasn’t touched to work with my VP2, but until then, my experience is having the 75 is markedly superior to the Davis 31. Temp specs are not as good obviously and not exactly a rigorous study, but I’ve tested side by side with an ASOS at -8F and it was right on. Not trying to convince anyone, but just my experience ...
How much of the difference is there between the 75 & psych-dyne?
Usually pretty spot on. Within 1F in dew point. Sometimes 2F. The nice thing about the 75 is you can put it right in the intake of the psychro dyne to verify temp and dew point. I know some others are using the 75 so they may be able to provide more input in terms of temp/hum accuracy of the 75 across the extreme ranges
That’s good! Have you ever done a comparison between the 75 & 31 in regards to air temp?
How did your 31 compared to the psychro-dyne?
The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.I'm more of a leg guy anyway.
Psychro dyne is made by Belfort one of the most trusted names in meteorological instruments.
The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.
Psychro dyne is made by Belfort one of the most trusted names in meteorological instruments.
The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.
If I’m not mistaken, I’m the NWS ASOS training manual, they say to use the psychro-dyne to verify the ASOS’ DP readings.
https://training.weather.gov/nwstc/DATAACQ/d.ASOShuman/ASOSTemp.htm
Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
You can see it was more stable before and after the storm passed. When that gust front first hits it becomes a pretty dynamic situation. I come from the meteorological research side of things so I find all of these brief fluctuations fascinating. I don't think someone coming to my site is worried about a few % RH during a storm when they see a rain rate of 7"/hr and 1.25" through the tipper in a half hour, but that's just me.Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
Hmmm... a 12% swing down in humidity in 2 minutes (3:46-3:48) while it's raining? And the temp only changed 0.3F? That would drive me nuts. I already had to write a routine to compute the 5 minute rolling average for humidity & dew point read by the 31 in the FARS so that I wasn't getting wild fluctuations in data sent to the website and CWOP (NWS prefers smoothed data).
To the extent it's possible, I don't want to be reporting microscale effects. People come to my site or check one of my data feeds to see what the weather is like in the city center, not to learn when a butterfly has flapped its wings.
As always, your mileage may vary, but maybe the 75 isn't for me.
You can see it was more stable before and after the storm passed. When that gust front first hits it becomes a pretty dynamic situation. I come from the meteorological research side of things so I find all of these brief fluctuations fascinating. I don't think someone coming to my site is worried about a few % RH during a storm when they see a rain rate of 7"/hr and 1.25" through the tipper in a half hour, but that's just me.Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
Hmmm... a 12% swing down in humidity in 2 minutes (3:46-3:48) while it's raining? And the temp only changed 0.3F? That would drive me nuts. I already had to write a routine to compute the 5 minute rolling average for humidity & dew point read by the 31 in the FARS so that I wasn't getting wild fluctuations in data sent to the website and CWOP (NWS prefers smoothed data).
To the extent it's possible, I don't want to be reporting microscale effects. People come to my site or check one of my data feeds to see what the weather is like in the city center, not to learn when a butterfly has flapped its wings.
As always, your mileage may vary, but maybe the 75 isn't for me.
This is exactly what Davis hates to hear. If you think about it this thread will live on forever and it's not great for Davis advertising. You aren't the only person I'm sure with same thoughts about holding off purchase.
Best thing Davis can do is address and fix problem quickly or thread will be 100 pages long eventually and come up on every Google search for years.
I can't remember if we confirmed the SHT15 also had high bias.
The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.I'm more of a leg guy anyway.
Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
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RH on the old 75 only maxed out at 96% (31 had only been hitting 94%) last night. I put another coat of conformal coating on the new one this morning so it may not be until later tomorrow that I'll get to install it.
The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.I'm more of a leg guy anyway.
Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
[ You are not allowed to view attachments ]
RH on the old 75 only maxed out at 96% (31 had only been hitting 94%) last night. I put another coat of conformal coating on the new one this morning so it may not be until later tomorrow that I'll get to install it.
Those are some wild swings. I actually went in and took the filter off my 31 yesterday evening. I love the faster response time, tho my only main concern is the fan blowing all that air straight to the humidity sensor part. I wonder how long before it starts to dry out or just go bonkers, anyone know? I was very reluctant to for that reason, but what's done is done. I will enjoy my fast response time \:D/
My temp is still spot on. People with filters are already seeing humidity drift anyway so I don't really worry about it. We all do this for ourselves so whatever gives you the most enjoyment I say go for it. We all want the best possible accuracy, but there's so many sensors with different specs and different ways to come up with an "official" 2m ambient temp that there's always going to be some discrepancies...different shielding, different specs, different response, different smoothing/averaging algorithms, etc.The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.I'm more of a leg guy anyway.
Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
[ You are not allowed to view attachments ]
RH on the old 75 only maxed out at 96% (31 had only been hitting 94%) last night. I put another coat of conformal coating on the new one this morning so it may not be until later tomorrow that I'll get to install it.
Those are some wild swings. I actually went in and took the filter off my 31. I love the faster response time, tho my only main concern is the fan blowing all that air straight to the humidity sensor part. I wonder how long before it starts to dry out or just go bonkers, anyone know? I was very reluctant to for that reason, but what's done is done. I will enjoy my fast response time \:D/
We all want the best possible accuracy, but there's so many sensors with different specs and different ways to come up with an "official" 2m ambient temp that there's always going to be some discrepancies...different shielding, different specs, different response, different smoothing/averaging algorithms, etc.Yep, and as we strive for more accuracy we give up a little in consistency. If I can get accuracy that at least approaches that of historical records taken with manual equipment in Stevenson screens without spending hundreds extra to get a fraction of a degree accuracy, I'm happy. I just want to know what it feels like outside and keep records of highs and lows and such. Of course my "official" highs and lows may be slightly different than a neighbor with high-end equipment, but at least I'm comparing apples to apples, blissfully ignorant of any sensor drift in my uncalibrated instruments anyway. As long as it's in the ballpark with other stations in the region I don't worry. I also have a spare ISS and other equipment I can compare it to.
My temp is still spot on. People with filters are already seeing humidity drift anyway so I don't really worry about it. We all do this for ourselves so whatever gives you the most enjoyment I say go for it. We all want the best possible accuracy, but there's so many sensors with different specs and different ways to come up with an "official" 2m ambient temp that there's always going to be some discrepancies...different shielding, different specs, different response, different smoothing/averaging algorithms, etc.The very best is Assmann psychrometer which is used as reference instrument tool. A little out of my price range however.I'm more of a leg guy anyway.
Had a decent storm go through yesterday while I wasn't home. You can pick up some pretty cool microscale effects in temp/dew with the FARS, 75, and 1-min intervals. For those unfamiliar with the Davis text files, it's Temp-MaxTemp-MinTemp-RH-Dew
[ You are not allowed to view attachments ]
RH on the old 75 only maxed out at 96% (31 had only been hitting 94%) last night. I put another coat of conformal coating on the new one this morning so it may not be until later tomorrow that I'll get to install it.
Those are some wild swings. I actually went in and took the filter off my 31. I love the faster response time, tho my only main concern is the fan blowing all that air straight to the humidity sensor part. I wonder how long before it starts to dry out or just go bonkers, anyone know? I was very reluctant to for that reason, but what's done is done. I will enjoy my fast response time \:D/
I may gobble up a few 75s on Newark or Mouser before they become too hard to find. For ~$30 each, if they croak or drift too much in a year I could just swap another one in. By then we'll have a pin 35 that maybe we can adapt to a VP2.
From the side by sides I’ve done, the unmodified 75 runs consistently drier than the Davis-mounted 31 in the midrange as low as humidity in the 20s. (And I stress it is unmodified). That said, it’s not perfect and is still a Sensirion. It struggles to hit 100%, but gets there on occasion. It hits 98 and 99 regularly. It will still exhibit a wet bias if in high humidity for a prolonged period and I’d say it may have a slight wet bias generally, but it compares really closely to my psycho-dyne. I’d love to find a way to get a 31 or 35 that Davis hasn’t touched to work with my VP2, but until then, my experience is having the 75 is markedly superior to the Davis 31. Temp specs are not as good obviously and not exactly a rigorous study, but I’ve tested side by side with an ASOS at -8F and it was right on. Not trying to convince anyone, but just my experience ...
How much of the difference is there between the 75 & psych-dyne?
Usually pretty spot on. Within 1F in dew point. Sometimes 2F. The nice thing about the 75 is you can put it right in the intake of the psychro dyne to verify temp and dew point. I know some others are using the 75 so they may be able to provide more input in terms of temp/hum accuracy of the 75 across the extreme ranges
That’s good! Have you ever done a comparison between the 75 & 31 in regards to air temp?
How did your 31 compared to the psychro-dyne?
The psychro dyne is dead on next to ASOS for temp and humidity. I’ve never found a difference in temp between the 75 and 31 when I’ve run them side by side. I could maybe do some more tests to get you some numeric answers. The Davis 31 is dead on for temp with the psychrodyne, but high on dewpoint usually by up to 4F, which is consistent with the comparison to ASOS. I have had the 75 next to an ASOS from -8F up to about 90F and it’s always been exactly on. I know the specs aren’t as good, but practically it seems to be a really good performer...
Thanks to some of these guys for going to Davis so they at least know the issue with their sensor. . I purchased the Acurite with the 31 after reading about it in this thread. It is really very good. I wish Davis’ 31 performed this way on the humidity side
You have your new 75 up and running?Not yet. I decided to give it another coat of conformal coating. I'll install it tomorrow evening once the shade hits the ISS in the evening.
You have your new 75 up and running?Not yet. I decided to give it another coat of conformal coating. I'll install it tomorrow evening once the shade hits the ISS in the evening.
How much of a variance in terms of RH did the psycho-dyne showed in comparison to the SHT-31?
Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
These are the sensor update rates filter or not.
ISS Weather Variable Update Intervals
(Transmitter ID Dependent)
Wind speed: . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Wind direction: . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Accumulated rainfall: . . . . . . . . . . . . . . . 20 to 24 seconds
Rain rate: . . . . . . . . . . . . . . . . . . . . . . . . 20 to 24 seconds
Outside temperature: . . . . . . . . . . . . . . . 10 to 12 seconds
Outside humidity: . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Ultraviolet radiation: . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Solar radiation: . . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
https://www.davisinstruments.com/product_documents/weather/manuals/07395-249_IM_06152.pdf
We spoke of this quite a while back, leaving the filter off has no real benefit, but then, maybe leaving it on doesn't either. #-o :grin:perhaps not worth taking the filter off.Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
These are the sensor update rates filter or not.
ISS Weather Variable Update Intervals
(Transmitter ID Dependent)
Wind speed: . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Wind direction: . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Accumulated rainfall: . . . . . . . . . . . . . . . 20 to 24 seconds
Rain rate: . . . . . . . . . . . . . . . . . . . . . . . . 20 to 24 seconds
Outside temperature: . . . . . . . . . . . . . . . 10 to 12 seconds
Outside humidity: . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Ultraviolet radiation: . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Solar radiation: . . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
https://www.davisinstruments.com/product_documents/weather/manuals/07395-249_IM_06152.pdf
We spoke of this quite a while back, leaving the filter off has no real benefit, but then, maybe leaving it on doesn't either. #-o :grin:perhaps not worth taking the filter off.Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
These are the sensor update rates filter or not.
ISS Weather Variable Update Intervals
(Transmitter ID Dependent)
Wind speed: . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Wind direction: . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Accumulated rainfall: . . . . . . . . . . . . . . . 20 to 24 seconds
Rain rate: . . . . . . . . . . . . . . . . . . . . . . . . 20 to 24 seconds
Outside temperature: . . . . . . . . . . . . . . . 10 to 12 seconds
Outside humidity: . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Ultraviolet radiation: . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Solar radiation: . . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
https://www.davisinstruments.com/product_documents/weather/manuals/07395-249_IM_06152.pdf
Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
These are the sensor update rates filter or not.
ISS Weather Variable Update Intervals
(Transmitter ID Dependent)
Wind speed: . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Wind direction: . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Accumulated rainfall: . . . . . . . . . . . . . . . 20 to 24 seconds
Rain rate: . . . . . . . . . . . . . . . . . . . . . . . . 20 to 24 seconds
Outside temperature: . . . . . . . . . . . . . . . 10 to 12 seconds
Outside humidity: . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Ultraviolet radiation: . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Solar radiation: . . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
https://www.davisinstruments.com/product_documents/weather/manuals/07395-249_IM_06152.pdf
I know the update rates. All I'm saying is I'm seeing less change per update without the filter than when I saw the last time I had no filter. As opposed to .2-.5° or so change per update, I'm either seeing no change or mainly .1°, occasionally .2°. I suppose I just find it odd and perhaps not worth taking the filter off.
Oddly enough, after taking the filter off yesterday evening, I'm really not seeing that much better response time than with it on, even with a bit drier of air in place (48%). I remember accidentally leaving it off last summer and sometimes seeing .3-4 change in an update, but now it's almost as if I still have the filter on, and this with a 24 cfm fan so it's definitely bringing in some serious ambient air with it. Hmmm...
I should add that the humidity is changing alot more than usual, just not as much as the temp.
These are the sensor update rates filter or not.
ISS Weather Variable Update Intervals
(Transmitter ID Dependent)
Wind speed: . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Wind direction: . . . . . . . . . . . . . . . . . . . . 2.5 to 3 seconds
Accumulated rainfall: . . . . . . . . . . . . . . . 20 to 24 seconds
Rain rate: . . . . . . . . . . . . . . . . . . . . . . . . 20 to 24 seconds
Outside temperature: . . . . . . . . . . . . . . . 10 to 12 seconds
Outside humidity: . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Ultraviolet radiation: . . . . . . . . . . . . . . . . 50 seconds to 1 minute
Solar radiation: . . . . . . . . . . . . . . . . . . . 50 seconds to 1 minute
https://www.davisinstruments.com/product_documents/weather/manuals/07395-249_IM_06152.pdf
I know the update rates. All I'm saying is I'm seeing less change per update without the filter than when I saw the last time I had no filter. As opposed to .2-.5° or so change per update, I'm either seeing no change or mainly .1°, occasionally .2°. I suppose I just find it odd and perhaps not worth taking the filter off.
Were you using the Davis filter or the Sensirion filter?
Interesting that Campbell Scientific sells their version of the SHT-75...
https://www.campbellsci.com/cs215-l
Interesting that Campbell Scientific sells their version of the SHT-75...
https://www.campbellsci.com/cs215-l
Quoted from the data sheet:
"The CS215 uses the Sensirion SHT75, a combined relative humidity and temperature element, to provide accurate, stable measurements. The Sensirion SHT75 element is field-replaceable, eliminating the downtime typically required for the recalibration process. The CS215 outputs an SDI-12 signal that's measurable by many Campbell Scientific dataloggers."
What's the SDI-12 signal? Compatible with Sensibus?
What's the SDI-12 signal? Compatible with Sensibus?
For what it's worth, I just took my Belfort 566 psychrometer outside. We are showing 97% RH on my Davis ISS and 95% on the Davis Temp/Hum station. I believe that these are both SHT-11 (or -15) and definitely not SHT-31.
Using distilled water I got 65°F dry bulb and 64°F wet bulb.
The slide rule shows about 94% RH a web calculator gives 94.88% RH. http://linricsoftw.web701.discountasp.net/webpsycalc.aspx (http://linricsoftw.web701.discountasp.net/webpsycalc.aspx)
I ordered one of those Sensirion SHT-31 eval boards from Mouser.
Greg H.
Hmm. Interesting. Let us know the results using the 31
This morning the humidity was higher and I had the chance to check the Sensirion eval board. I have it placed in my NovaLynx thermometer housing and the shelter is in the shade this time of day.
Here is what I saw:
ISS Humidity: 92%
T/H Station: 88%
SHT-31 eval: 88.86% (Temp was 65.78°F)
Belfort Psychrometer Wet/Dry: 66°F Dry, 63½°F Wet giving 87.58%. Another reading was 67°F and 64°F for 85.38%
Conditions were changing, especially on the Sensirion board and Belfort. I tried to stay close to the therm shelter and the Sensirion while using the Belfort.
Dew Point per the Belfort was 62°F to 63°F and 63°F on the Davis ISS.
I have a feeling that this is one of those "measure it with a micrometer, mark it with chalk and cut it with an axe" kind of things...
Greg H.
Glad you posted that if good stuff I need something. I ordered some of those filters also primarily for the metoshield I have coming in couple weeks. Less restriction inside temperature chamber the better I would think.
I found this also. http://ecobondit.com/ecobond-products/
http://ecobondit.com/what-we-stick-too/
and this https://www.amazon.com/Supertite-Universal-Industrial-Strength-0-63oz/dp/B077KGT3K7/ref=sr_1_8?ie=UTF8&qid=1532993103&sr=8-8&keywords=Eco-Bond+Adhesives
MY THOUGHT - Use a piece of cotton string, cause cotton don't out-gas, for a mechanical attachment.
Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
How about using one of your nylon panty hose, the one with a run it. :lol: ..Just wrap the whole sensor. I've heard they make a excellent fine dust filter.Firstly...you swore you wouldn't tell.... Secondly, this might actually work if secured well enough. Hmmmm..
How about using one of your nylon panty hose, the one with a run it. :lol: ..Just wrap the whole sensor. I've heard they make a excellent fine dust filter.Firstly...you swore you wouldn't tell.... Secondly, this might actually work if secured well enough. Hmmmm..
Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
Really? No rubber... Why not?
Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
Really? No rubber... Why not?
All rubber I've been around has a strong odor. The odor is the gaseous toxins being released. Unless it isn't the type of toxin that wouldn't be harmful. Not sure :?:
Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
Really? No rubber... Why not?
All rubber I've been around has a strong odor. The odor is the gaseous toxins being released. Unless it isn't the type of toxin that wouldn't be harmful. Not sure :?:
Ahh .. I got ya.
Well if its pantyhose, better make it Silk stockings instead of nylon...just in case its an issue too. besides, the silk is a lot more durable and finer weave ..So Iv'e heard :-)
Actually, you can go on eBay and by a pillow case from some Chinese sellers for a lot cheaper. Get a low momme weight.Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
Really? No rubber... Why not?
All rubber I've been around has a strong odor. The odor is the gaseous toxins being released. Unless it isn't the type of toxin that wouldn't be harmful. Not sure :?:
Ahh .. I got ya.
Well if its pantyhose, better make it Silk stockings instead of nylon...just in case its an issue too. besides, the silk is a lot more durable and finer weave ..So Iv'e heard :-)
Real silk is expensive. https://www.stockingirl.com/product/SGSS2.html
Back to the Supertite Eco Glue
Ya know, I think I'll try a small diameter spring (like in your ball point pen, but longer) that's wraps around the sensor board. If necessary I'll cut the sensor board to accommodate it, but pretty sure I'll find an appropriate spring. At the very least I'll put notches at both ends of the board to keep the spring stationary.That's a pretty good Idea. Spring might want to roll, but if its fairly stiff it should work.
Actually, you can go on eBay and by a pillow case from some Chinese sellers for a lot cheaper. Get a low momme weight.Something like a rubber band would be the shiz nit. But the the filter cap is still so tiny, even a thin rubber band would likely block the hole. There is almost no extra surface area for any kind of mechanical fasteners i can think of.
Can't use rubber. Not sure about nylon.
Really? No rubber... Why not?
All rubber I've been around has a strong odor. The odor is the gaseous toxins being released. Unless it isn't the type of toxin that wouldn't be harmful. Not sure :?:
Ahh .. I got ya.
Well if its pantyhose, better make it Silk stockings instead of nylon...just in case its an issue too. besides, the silk is a lot more durable and finer weave ..So Iv'e heard :-)
Real silk is expensive. https://www.stockingirl.com/product/SGSS2.html
Back to the Supertite Eco Glue
Ohh and Thanks for the link. \:D/
That's what the notches are for, just make sure they're in line with the sensor.Ya know, I think I'll try a small diameter spring (like in your ball point pen, but longer) that's wraps around the sensor board. If necessary I'll cut the sensor board to accommodate it, but pretty sure I'll find an appropriate spring. At the very least I'll put notches at both ends of the board to keep the spring stationary.That's a pretty good Idea. Spring might want to roll, but if its fairly stiff it should work.
actually, I meant even with notches, if the spring was too 'flimsy' it may still want to roll off the cap. but maybe not. if you went the short distance across.That's what the notches are for, just make sure there in line with the sensor.Ya know, I think I'll try a small diameter spring (like in your ball point pen, but longer) that's wraps around the sensor board. If necessary I'll cut the sensor board to accommodate it, but pretty sure I'll find an appropriate spring. At the very least I'll put notches at both ends of the board to keep the spring stationary.That's a pretty good Idea. Spring might want to roll, but if its fairly stiff it should work.
I'm spring shopping tomorrow. With an adequate one, which shouldn't be hard to find, I think it'll work fine.
Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:Yeah, I guess so. I figured the thin, light weight or mm weight would be plenty breathable.
MY THOUGHT, Part Deux: How about a small nylon tie-wrap?I was just about to add " or monofilament line" when the stainless wire hit me. Also after realizing that the old cap mounting holes are not used, your idea about the cotton string is now looking like a possibility too. Just no way to garrantee it maintain pressure against the cap.
Interesting. SHT31 (turquoise) vs SHT11 (black) Plot shows a RH crossover point at ~86%. Between 60%-86% the SHT31 shows 3-5% higher RH. Above 86% SHT11 starts showing higher RH and continues to till 10:30 AM this morning as it's till above 95% RH here.
Disregard prior to 5pm. SHT11 Sensor just came on-line.
Note: Both Temps were tracking within .5 deg and the Temp at crossover was 78 deg F.
SHT11 is in a Passive Rad Shield, 6+ year old and just baked and re-hydrated Sunday.
SHT31 is in a FARS & is about a week old.
Good point. I didn't consider that. However, on this particular evening/afternoon there was no sun as a storm blew in around noon and it was dark overcast the rest of the day. Not sure how that affects the results either.Interesting. SHT31 (turquoise) vs SHT11 (black) Plot shows a RH crossover point at ~86%. Between 60%-86% the SHT31 shows 3-5% higher RH. Above 86% SHT11 starts showing higher RH and continues to till 10:30 AM this morning as it's till above 95% RH here.
Disregard prior to 5pm. SHT11 Sensor just came on-line.
Note: Both Temps were tracking within .5 deg and the Temp at crossover was 78 deg F.
SHT11 is in a Passive Rad Shield, 6+ year old and just baked and re-hydrated Sunday.
SHT31 is in a FARS & is about a week old.
Looks like the lines cross not long after sunset.
You might, at some point, think to reverse the shield arrangement - placing the SHT11 in the FARS and the 31 in the passive shield. Reason I say that is because a FARS is going to produce a higher temperature on many nights (except overcast and windy) because it better protects against radiational cooling. The dew point should always be the same in both shields, theoretically, assuming the sensors have no bias or an identical bias. So, all things being equal, the FARS will generally have the lower humidity reading.
Dendrite, would you be able to break down the steps involved in hooking up an SHT75 to the SIM?I used this for reference.
As I understand it, you can snip the wire off an old SHT sensor, but which wires go to which leads?
You also mentioned "conformal coating". Could you describe that process? Looks like just slathering on some silicone-like substance over the leads to insulate them.
There appears to be some kind of "jack" (for lack of a better term) that the sensor leads slip into which then attaches to the cable going to the SIM. I assume you can also procure that part from mouser.com (along with the sensor), but what is it called?
If you are busy or unavailable, no sweat.
1.2 Sockets and Soldering
For maintain high accuracy specifications the sensor shall
not be soldered. Sockets may be used such as “Preci-dip /
Mill-Max R851-83-004-20-001” or similar.
Standard wave soldering ovens may be used at maximum
235°C for 20 seconds. For manual soldering contact time
must be limited to 5 seconds at up to 350°C7.
After wave soldering the devices should be stored at
>75%RH for at least 12h to allow the polymer to rehydrate.
Alternatively the re-hydration process may be
performed at ambient conditions (>40%RH) during more
than 5 days.
In no case, neither after manual nor wave soldering, a
board wash shall be applied. In case of application with
exposure of the sensor to corrosive gases the soldering
pads of pins and PCB shall be sealed to prevent loose
contacts or short cuts.
You saved me a trip to the hardware store. I found some braided wire for hanging pictures in the house and tried it on my spare 31 and it works just fine, only one or two strands is plenty. I would say you don't really need to do the side thing, over top will be fine, especially for older eyes.Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:I realized the mounting holes for the Davis cap are not being used. Therefore... A double wrap of thin stainless wire through the old mount holes, each lying on either edge of the filter cap, twist wires together on the back and Done.
You saved me a trip to the hardware store. I found some braided wire for hanging pictures in the house and tried it on my spare 31 and it works just fine, only one or two strands is plenty. I would say you don't really need to do the side thing, over top will be fine, especially for older eyes.Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:I realized the mounting holes for the Davis cap are not being used. Therefore... A double wrap of thin stainless wire through the old mount holes, each lying on either edge of the filter cap, twist wires together on the back and Done.
Thanks!
What's good for the goose, is good for the gander. If I understand this filter correctly, it allows air to pass through, but also makes it waterproof when sealed correctly. I believe it is suppose to help the sensor from becoming saturated for you folks in the humid parts of the country. I don't think I really need this filter, as I not really experiencing problems like the others, but what the hell, can't hurt.Speaking of (sort of) You think this SF2 filter would have any advantages or disadvantages in passive shield setup?You saved me a trip to the hardware store. I found some braided wire for hanging pictures in the house and tried it on my spare 31 and it works just fine, only one or two strands is plenty. I would say you don't really need to do the side thing, over top will be fine, especially for older eyes.Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:I realized the mounting holes for the Davis cap are not being used. Therefore... A double wrap of thin stainless wire through the old mount holes, each lying on either edge of the filter cap, twist wires together on the back and Done.
Thanks!
... If I understand this filter correctly, it allows air to pass through, but also makes it waterproof when sealed correctly. I believe it is suppose to help the sensor from becoming saturated for you folks in the humid parts of the country....Speaking of (sort of) You think this SF2 filter would have any advantages or disadvantages in passive shield setup?You saved me a trip to the hardware store. I found some braided wire for hanging pictures in the house and tried it on my spare 31 and it works just fine, only one or two strands is plenty. I would say you don't really need to do the side thing, over top will be fine, especially for older eyes.Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:I realized the mounting holes for the Davis cap are not being used. Therefore... A double wrap of thin stainless wire through the old mount holes, each lying on either edge of the filter cap, twist wires together on the back and Done.
Thanks!
Thanks, dendrite! I think that will help a lot of readers, myself included.Like we were talking about before though...
Thanks, dendrite! I think that will help a lot of readers, myself included.Like we were talking about before though...
If you don't like almost instantaneous response (like raw, non-averaged ASOS data) this may not be for you. Especially if you are using a custom FARS with much more CFM passing through it than the Davis fans. If that isn't a detriment to someone, then I think that person will love the 75. Of course if you find a way to put a filter over it or use the Davis stock fan, that will knock the response down. I would think a passive shield would knock it down even further, but given the recent passive vs FARS tests, who knows?
WHAT! Waterproof :shock:
I totally missed that. I thought it was just less "obstructive" and allowed moving air closer contact to the sensor than the Big Davis Filter. Also the other reason it was looked at was to add a dust filter in addition to the Davis filter to lessen the amount of contaminates causing premature aging of the Humidity sensor.
You'd have to find another way, but doable I'd think.... If I understand this filter correctly, it allows air to pass through, but also makes it waterproof when sealed correctly. I believe it is suppose to help the sensor from becoming saturated for you folks in the humid parts of the country....Speaking of (sort of) You think this SF2 filter would have any advantages or disadvantages in passive shield setup?You saved me a trip to the hardware store. I found some braided wire for hanging pictures in the house and tried it on my spare 31 and it works just fine, only one or two strands is plenty. I would say you don't really need to do the side thing, over top will be fine, especially for older eyes.Can't be just any silk has to be breathable. Pillow cases aren't the same as pantyhose. :lol:I realized the mounting holes for the Davis cap are not being used. Therefore... A double wrap of thin stainless wire through the old mount holes, each lying on either edge of the filter cap, twist wires together on the back and Done.
Thanks!
WHAT! Waterproof :shock:
I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
Yeah, I manhandled it too, just to see how it would go. Now that I have, I'll be using latex gloves, then washing my hands with them on before handling one of the other filters I bought (5).I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
But I noticed 2 things while reading that link you provided.
1. touching the membrane can contaminate with oils and reduce the amount of humidity that can transfer to the sensor. #-o Yeah.. I touched it... like a lot. ](*,) I thought it was just a screen.
Yeah, I manhandled it too, just to see how it would go. Now that I have, I'll be using latex gloves, then washing my hands with them on before handling one of the other filters I bought (5).I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
But I noticed 2 things while reading that link you provided.
1. touching the membrane can contaminate with oils and reduce the amount of humidity that can transfer to the sensor. #-o Yeah.. I touched it... like a lot. ](*,) I thought it was just a screen.
Well, it's certainly more protective than the stock filter, but certainly more difficult to mount properly.Yeah, I manhandled it too, just to see how it would go. Now that I have, I'll be using latex gloves, then washing my hands with them on before handling one of the other filters I bought (5).I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
But I noticed 2 things while reading that link you provided.
1. touching the membrane can contaminate with oils and reduce the amount of humidity that can transfer to the sensor. #-o Yeah.. I touched it... like a lot. ](*,) I thought it was just a screen.
So, I take it this sensirion SF2 filter is now all the craze? I might just have to get me one, or two.
Well, it's certainly more protective than the stock filter, but certainly more difficult to mount properly.Yeah, I manhandled it too, just to see how it would go. Now that I have, I'll be using latex gloves, then washing my hands with them on before handling one of the other filters I bought (5).I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
But I noticed 2 things while reading that link you provided.
1. touching the membrane can contaminate with oils and reduce the amount of humidity that can transfer to the sensor. #-o Yeah.. I touched it... like a lot. ](*,) I thought it was just a screen.
So, I take it this sensirion SF2 filter is now all the craze? I might just have to get me one, or two.
Yeah, I manhandled it too, just to see how it would go. Now that I have, I'll be using latex gloves, then washing my hands with them on before handling one of the other filters I bought (5).I was noticing when putting on the filter that the rubbery substance around the sensor allows for what I think would be a good seal if the filter is smoothed off and the wire torqued down enough. At least you would avoid a sealant if it works.Agreed.
But I noticed 2 things while reading that link you provided.
1. touching the membrane can contaminate with oils and reduce the amount of humidity that can transfer to the sensor. #-o Yeah.. I touched it... like a lot. ](*,) I thought it was just a screen.
So, I take it this sensirion SF2 filter is now all the craze? I might just have to get me one, or two.
Hit 97% on the 75 this morning despite BKN/OVC skies and no fog (just some light dew). I see jerryg is up to 99% RH this morning...maybe he snuck a 100% in there between Mesowest obs.
I also note there is very little difference in specification between the SHT15 and SHT7x. My VP2 came with an SHT11 so I have ordered a couple of SHT15s and will swap out the SHT11.
All three are now in the same range of humidity, almost two hours to get there.
Didn't one of those 31s hit 100% this morning? Maybe they haven't experienced much drift yet?All three are now in the same range of humidity, almost two hours to get there.
For me this is a red flag because my 31's always run 5%+ above actual humidity (moist warm environment I assume you are in on the Gulf coast at 87°) even my new units do. And if they all are the same tells me the 75 isn't much better and running high.
All three are now in the same range of humidity, almost two hours to get there.
For me this is a red flag because my 31's always run 5%+ above actual humidity (moist warm environment I assume you are in on the Gulf coast at 87°) even my new units do. And if they all are the same tells me the 75 isn't much better and running high.
Yes, lets see if it stays near the 31 after saturation all day that would be my main concern and tells me it's just a senserion issue with all their sensors, some worse than others.
Just to inform you i am 10 miles se of kvct and 12 miles nw of port lavaca metar. Port lavaca station is located a few miles from lavaca bay and my readings very seldom agree because i am inland from the bay and on the other side i generally run wetter than kvct being in the country over grass and not over gravel. The rw station being on the roof of a building matches the runway and gravel of kvct lol. So i am on an island by myself with the closest pws about 7 miles away, i have to run my own comparisons lol. Another thing kvct is at 115 feet and port lavaca is at 27 feet and i am at 59 feet. I have always found it strange that the metar near the bay always has lower humidity readings than most, strange being near that much water. Of course the temps are higher due to the fact they get the warm air currents off of the water and keeps their temps up at night and cooler in the daytime. I don't get any cooling from the bay until the sea breeze kicks in and then the temp drops in the after noon and the humidity goes up, makes it real hard to get a handle on things. Sometimes the sea breeze doesn't make it to kvct and i have a big temp and humidity difference.
Just to inform you i am 10 miles se of kvct and 12 miles nw of port lavaca metar. Port lavaca station is located a few miles from lavaca bay and my readings very seldom agree because i am inland from the bay and on the other side i generally run wetter than kvct being in the country over grass and not over gravel. The rw station being on the roof of a building matches the runway and gravel of kvct lol. So i am on an island by myself with the closest pws about 7 miles away, i have to run my own comparisons lol. Another thing kvct is at 115 feet and port lavaca is at 27 feet and i am at 59 feet. I have always found it strange that the metar near the bay always has lower humidity readings than most, strange being near that much water. Of course the temps are higher due to the fact they get the warm air currents off of the water and keeps their temps up at night and cooler in the daytime. I don't get any cooling from the bay until the sea breeze kicks in and then the temp drops in the after noon and the humidity goes up, makes it real hard to get a handle on things. Sometimes the sea breeze doesn't make it to kvct and i have a big temp and humidity difference.
That makes good sense. Elevation can also play a role too when it comes to DP.
here is a sample of reports from victoria and port lavaca metars and mine at 1 pm victoria temp 93 dp 71 h 48 port lavaca temp 92 dp 65 h 41 and mine temp 91 dp 72 h 54 That is a lot of variations to try to compare to my dp was pretty close to victoria but way off from port lavaca just too many variations to try and compare being i am half way in between the two. I just have to trust that my 29 dollar sensor is doing as good as it can without some type of calibrated instruments to compare to on site. Heck for my site i am right and they are wrong :lol:The 65 at PKV was very brief.
Current dewpoints
Jerry 1944z 67.8°
PKV 1940z 66.9°
VCT 1940z 68°
I know. I made that same point earlier...Current dewpoints
Jerry 1944z 67.8°
PKV 1940z 66.9°
VCT 1940z 68°
You can't just take one instantaneous reading from CWOP and compare it to airports several minutes ago. When I checked earlier, it was stagnant & sunny and his DPs were bouncing around by several degrees even within a matter of seconds. He has an SHT75 loaded into a FARS. It's like a caged monkey! You have to average several of his readings. That means sitting on his website for several minutes, recording at least a couple minutes of DP readings and then deriving an average.
Of course, comparing to reference stations is only a possible indication of a problem, not confirmation. That would require a calibrated device.
I know. I made that same point earlier...Current dewpoints
Jerry 1944z 67.8°
PKV 1940z 66.9°
VCT 1940z 68°
You can't just take one instantaneous reading from CWOP and compare it to airports several minutes ago. When I checked earlier, it was stagnant & sunny and his DPs were bouncing around by several degrees even within a matter of seconds. He has an SHT75 loaded into a FARS. It's like a caged monkey! You have to average several of his readings. That means sitting on his website for several minutes, recording at least a couple minutes of DP readings and then deriving an average.
Of course, comparing to reference stations is only a possible indication of a problem, not confirmation. That would require a calibrated device.
https://www.wxforum.net/index.php?topic=34658.msg355192#msg355192
What I was getting at is that they can all be different one hour and then lined up the next. Sorry, for not clarifying what I was getting at by posting the dewpoints. :-)
:lol:
He has an SHT75 loaded into a FARS. It's like a caged monkey!
here is a sample of reports from victoria and port lavaca metars and mine at 1 pm victoria temp 93 dp 71 h 48 port lavaca temp 92 dp 65 h 41 and mine temp 91 dp 72 h 54 That is a lot of variations to try to compare to my dp was pretty close to victoria but way off from port lavaca just too many variations to try and compare being i am half way in between the two. I just have to trust that my 29 dollar sensor is doing as good as it can without some type of calibrated instruments to compare to on site. Heck for my site i am right and they are wrong :lol:
In reference to the SF2 mounting issues...Then you have the issue of finding a way to mount it to the FARS mounting plate or the VP2 Passive shield mount. So either way there is some customizing going on .. not to mention, now you gotta pull out the soldering iron...and then encapsulation/epoxy/silicone.
Why not use Closedcube Breakout SHT31 solution that includes SHT31 in small PCB with mounting holes for the SF2 filter, and includes the SF2 filter. Then all you need to do is solder the 4 leads.
Closedcube makes a very small SHT31 breakout and they have a bit larger one they call PRO. I'm not sure what the difference is. Also their is a D (digital) version and an A (Analog) version. Has anyone determined if Davis uses the Analog or the Digital?
You need to keep in mind that the break out is i2c formatted and will not work with Davis iss.
The Davis uses the SHT31-LSSYou need to keep in mind that the break out is i2c formatted and will not work with Davis iss.
Maybe the Digital version is the i2c and the Analog is the one for Davis.
I got my Barani pro passive shield in a while ago and i got it up and running for test and so far it is working great in a short test time. The wind has been calm to light so far and with it calm the pro has been running .5f lower than the fars and when the wind has been up around 4 mph or more it has been running about 1 degree lower. I sure hope this proves out in the long term i will use it and get rid of the fan problem and maybe help the sensor with the high humidity problem.
The Davis uses the SHT31-LSSYou need to keep in mind that the break out is i2c formatted and will not work with Davis iss.
Maybe the Digital version is the i2c and the Analog is the one for Davis.
Well, as much as I hate to say this, looks like I'll be jumping on the "bash the 31" wet bias bandwagon. After weeks of scrutinizing even more than usual, I've come to the conclusion that I'm suffering the same symptoms, maybe just not quite as bad as everyone else. As a generality, I'm running 3-4F in dew higher than my "official buddies". The thing is, neighboring stations tend to run wet also, so makes me dubious, but yes, most are Davis's. My 11 and 15 behaved the same way, which also makes me wonder. I guess I'll dial back the humidity 2% and see how that looks for now. Crap...
Didn't want to proclaim the sky was falling until I truly gave my particular situation a thorough evaluation. Perhaps being in a drier climate does help mitigate the bias, but from my perspective, it's there. Taking out 2% has me perfectly in-line.... for now..... ](*,)Well, as much as I hate to say this, looks like I'll be jumping on the "bash the 31" wet bias bandwagon. After weeks of scrutinizing even more than usual, I've come to the conclusion that I'm suffering the same symptoms, maybe just not quite as bad as everyone else. As a generality, I'm running 3-4F in dew higher than my "official buddies". The thing is, neighboring stations tend to run wet also, so makes me dubious, but yes, most are Davis's. My 11 and 15 behaved the same way, which also makes me wonder. I guess I'll dial back the humidity 2% and see how that looks for now. Crap...Welcome aboard and about time.
69.1°F with 98% RH already and clear skies at 9pm EDT. This should be a good night to see if the new SHT75 can hit 99% or 100%.
69.1°F with 98% RH already and clear skies at 9pm EDT. This should be a good night to see if the new SHT75 can hit 99% or 100%.
Sounds like some really FROGGY weather...you down in the Louisiana bayous?
Well, as much as I hate to say this, looks like I'll be jumping on the "bash the 31" wet bias bandwagon. After weeks of scrutinizing even more than usual, I've come to the conclusion that I'm suffering the same symptoms, maybe just not quite as bad as everyone else. As a generality, I'm running 3-4F in dew higher than my "official buddies". The thing is, neighboring stations tend to run wet also, so makes me dubious, but yes, most are Davis's. My 11 and 15 behaved the same way, which also makes me wonder. I guess I'll dial back the humidity 2% and see how that looks for now. Crap...
Welcome aboard and about time.
I can confirm Davis has made shipping changes but I'm skeptical that's the issue. Haven't figured out yet because the Acurite SHT31 version doesn't display the same high bias. I'm also testing on my NEW just built 2 days ago outdoor shaded porch and it's running close to 4-5% lower humidity all the time except in the morning dew when they all come together around 97% today. It's not the LCC version however and isn't embedded into plastic like the Davis either.
Yes.It’s frustrating and promising all at the same time.Well, as much as I hate to say this, looks like I'll be jumping on the "bash the 31" wet bias bandwagon. After weeks of scrutinizing even more than usual, I've come to the conclusion that I'm suffering the same symptoms, maybe just not quite as bad as everyone else. As a generality, I'm running 3-4F in dew higher than my "official buddies". The thing is, neighboring stations tend to run wet also, so makes me dubious, but yes, most are Davis's. My 11 and 15 behaved the same way, which also makes me wonder. I guess I'll dial back the humidity 2% and see how that looks for now. Crap...
Welcome aboard and about time.
I can confirm Davis has made shipping changes but I'm skeptical that's the issue. Haven't figured out yet because the Acurite SHT31 version doesn't display the same high bias. I'm also testing on my NEW just built 2 days ago outdoor shaded porch and it's running close to 4-5% lower humidity all the time except in the morning dew when they all come together around 97% today. It's not the LCC version however and isn't embedded into plastic like the Davis either.
Here's my 75 before I sealed it with the silicone conformal coating.
[ You are not allowed to view attachments ]
I just cut the sensor off of an old Davis temp/hum. You can see how the wiring goes in my pic. The connector I used required no soldering although you could get a connector with pins that you could solder the wires to. I just make a clean snip of the wires and insert them into the connector and then gently close it to make the connection. The 75 already comes with the 10K pull up resistor between pins 1 and 4 so you don’t need to worry about that. I sealed it with coating from that little bridge to the sensor down to the connector just to be on the safe side. The Davis cord is 6 wires, but the red and black don’t get used so you can just cut them away.Here's my 75 before I sealed it with the silicone conformal coating.
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So are there any how to make these 75's with clear precise instructions?. I've tried to follow but usually give up. :-(
I just cut the sensor off of an old Davis temp/hum. You can see how the wiring goes in my pic. The connector I used required no soldering although you could get a connector with pins that you could solder the wires to. I just make a clean snip of the wires and insert them into the connector and then gently close it to make the connection. The 75 already comes with the 10K pull up resistor between pins 1 and 4 so you don’t need to worry about that. I sealed it with coating from that little bridge to the sensor down to the connector just to be on the safe side. The Davis cord is 6 wires, but the red and black don’t get used so you can just cut them away.Here's my 75 before I sealed it with the silicone conformal coating.
[ You are not allowed to view attachments ]
So are there any how to make these 75's with clear precise instructions?. I've tried to follow but usually give up. :-(
http://www.newark.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&langId=-1&urlRequestType=Base&partNumber=53X2803&storeId=10194
I'd get a few. As openvista and I realized, they can be easy to break when you're first getting used to using them.
http://www.newark.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&langId=-1&urlRequestType=Base&partNumber=53X2803&storeId=10194
I'd get a few. As openvista and I realized, they can be easy to break when you're first getting used to using them.
Thanks I'll make up a couple and have ready for next summer for sure. I plan on continuing with the 31's this winter but may change mind if I find the 75's accurate enough as temperatures drop into -20 range. The 15's aren't great once temps go sub zero and specs show about the same is what worries me.
I never noticed an issue with my old 75 in near 0F temps during the winter I used it. Unfortunately we never had temps frigid enough (-15F or colder) to really test it out.
I had a 6470 probe from my soil station in my old 7714 passive shield from my WMII days. It only read whole numbers, but it was usually +/- 1F on those winter mornings. And yeah, the normal biases that you get used to with local stations on a day-to-day basis were still on par on those cold mornings. I have nothing scientific to give you though...just empirical. CW7491 had it testing accurately at -8F IIRC.I never noticed an issue with my old 75 in near 0F temps during the winter I used it. Unfortunately we never had temps frigid enough (-15F or colder) to really test it out.
What were you comparing too? Only way to know is have a side by side comparison. You can't trust others around you, I can't even trust the ASOS which started running +2° warm March 2017 Madis even picked the +2° jump.
Our city council members have taken notice finally after my persistence and some including me are pushing to have KVTN ASOS removed off of city property. It's actually dangerous we had multiple icing instances last winter and ASOS never reported ice formation because of warm bias.
The primary purpose of any ASOS is obviously to serve those who fly in and out of the associated airport. I assume by moving it off city property will take it well off the airport proper, no?I never noticed an issue with my old 75 in near 0F temps during the winter I used it. Unfortunately we never had temps frigid enough (-15F or colder) to really test it out.Our city council members have taken notice finally after my persistence and some including me are pushing to have KVTN ASOS removed off of city property. It's actually dangerous we had multiple icing instances last winter and ASOS never reported ice formation because of warm bias.
Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
Isn't VTN a first order station? Wouldn't that fall under the NWS?Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
If I were you and you're still not getting satisfaction, I'd give these guys a call and tell them you're concerns. If they can't help, they should be able to tell you who can. GL!
https://www.faa.gov/about/office_org/field_offices/fsdo/?state=NE
I have no idea what a "first order station" is.Isn't VTN a first order station?Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
If I were you and you're still not getting satisfaction, I'd give these guys a call and tell them you're concerns. If they can't help, they should be able to tell you who can. GL!
https://www.faa.gov/about/office_org/field_offices/fsdo/?state=NE
I may be wrong, but I think all ASOS stations up here are handled by NWS GYX. AWOS is maintained by FAA.The way I understand, ASOS's are NWS/FAA territory and AWOS's are airport management maintained. But as I said a while back on this matter, I'm sure one size doesn't fit all.
http://www.weather2000.com/1st_order_wbans.txtI have no idea what a "first order station" is.Isn't VTN a first order station?Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
If I were you and you're still not getting satisfaction, I'd give these guys a call and tell them you're concerns. If they can't help, they should be able to tell you who can. GL!
https://www.faa.gov/about/office_org/field_offices/fsdo/?state=NE
Basically your long term climatological sites.
I guess I'll dial back the humidity 2% and see how that looks for now. Crap...Granted, the air mass has changed little, but taking out 2% has put my 31 in it's wheelhouse because the readings are tracking to the point of astonishment. :shock: Shows how good this sensor should be. Too bad this can't be over the entire 0-100% range. ](*,)
Our local ASOS went haywire many years ago and stayed that way for years resulting in a +2-3 degree error. Stood out like a sore thumb. Frustrated me to no end. Finally one day out of the blue it was fixed. I inquired about it to the forecast office for our region and was told that a construction project several years before had cut the sensor bundle and never was repaired properly. They had to run a new line. Wala!
Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
If I were you and you're still not getting satisfaction, I'd give these guys a call and tell them you're concerns. If they can't help, they should be able to tell you who can. GL!
https://www.faa.gov/about/office_org/field_offices/fsdo/?state=NE
...
the sht31 temp appears to really be the strong point of the sensor and the humidity the weak point, too bad, could really be a great sensor otherwise.
If I may, lemme give you a little piece of advice; you go in "guns a blazing", they'll cut you off like a gangrenous appendage and there ain't squat you can do about it other than call your congressional rep in DC, then GL with that. You go in with "hey, I may have some safety related stuff for you guys", you're more likely to get an audience that will hear you beef. Whether they act upon it or not will be determined by how credible you're deemed, so have your ducks in a row.Who's they? I know the city owns the airport, now the question is who maintains the ASOS? If it's the city, then you're obviously on the right track.It's ongoing they ignore it so next step is getting city involved.Privately owned airport. Not sure who has the right to do what but if it was my property it would be gone.Well, I guess pilots could just rely on a windsock... ;)
If I were you and you're still not getting satisfaction, I'd give these guys a call and tell them you're concerns. If they can't help, they should be able to tell you who can. GL!
https://www.faa.gov/about/office_org/field_offices/fsdo/?state=NE
Thank you for this contact information. I'm going to contact the Orlando office of the FAA. I've been dealing with a bad ASOS at KORL Orlando Executive Airport reporting bad SLP. You can read what I've been dealing with here.
https://www.wxforum.net/index.php?topic=34821.0
...
the sht31 temp appears to really be the strong point of the sensor and the humidity the weak point, too bad, could really be a great sensor otherwise.
Yes the temperature sensor of the SHT31 is right on. Unfortunately, the humidity if off. Most people, myself included, desire accurate temperature vs. humidity accuracy. Too bad this sensor doesn’t capture both readings correctly and consistently.
...
the sht31 temp appears to really be the strong point of the sensor and the humidity the weak point, too bad, could really be a great sensor otherwise.
Yes the temperature sensor of the SHT31 is right on. Unfortunately, the humidity if off. Most people, myself included, desire accurate temperature vs. humidity accuracy. Too bad this sensor doesn’t capture both readings correctly and consistently.
I know I keep belaboring the point, but based on my experience with the home-brew SHT75 and especially the $17 Acurite SHT31, I’m not convinced this is a Sensirion issue as much as it’s a Davis issue.
...
the sht31 temp appears to really be the strong point of the sensor and the humidity the weak point, too bad, could really be a great sensor otherwise.
Yes the temperature sensor of the SHT31 is right on. Unfortunately, the humidity if off. Most people, myself included, desire accurate temperature vs. humidity accuracy. Too bad this sensor doesn’t capture both readings correctly and consistently.
I know I keep belaboring the point, but based on my experience with the home-brew SHT75 and especially the $17 Acurite SHT31, I’m not convinced this is a Sensirion issue as much as it’s a Davis issue.
...
the sht31 temp appears to really be the strong point of the sensor and the humidity the weak point, too bad, could really be a great sensor otherwise.
Yes the temperature sensor of the SHT31 is right on. Unfortunately, the humidity if off. Most people, myself included, desire accurate temperature vs. humidity accuracy. Too bad this sensor doesn’t capture both readings correctly and consistently.
I know I keep belaboring the point, but based on my experience with the home-brew SHT75 and especially the $17 Acurite SHT31, I’m not convinced this is a Sensirion issue as much as it’s a Davis issue.
So the 75 is running lower DP for sure?
Good to know I have a couple coming. Was wondering watching Jerry's.
The Acurite runs 5% lower humidity during the daytime and still manages to hit 98% in mornings like today when my almost new Davis SHT31 seems to be stuck at 97% now.
Have you guys been watching Jerry's new SHT75 dewpoint vs the airport?I've been following him on surface maps for a few days and he seems to be pretty close to what you'd expect being between VCT and the more humid PKV. You can see his dewpoint fluctuate depending on the component of onshore flow when the moisture boundary is between those 2 METAR sites.
Looks like to me the 75dp is running higher too. I would say on average 2° dp temperature.
The ASOS is only 8 miles away and recorded high temperature +2° over the SHT75 in passive shield for high yesterday which also seems excessive considering wind was well mixed with average wind speed 14 mph during high temperature period.
Correction Jerry posted another thread his high temp was 91. Uploads to cwop are spaced so missed the actual high.
Jerry https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=AT358&unit=0&timetype=LOCAL
ASOS https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVCT
I can confirm with cumulus both DP and humidity adjust with temperature sometimes every couple seconds and doesn't wait for humidity change.Not to go OT, but I’ll have to look into Cumulus more. You confused me a bit there...with Cumulus, DP and RH change every few seconds, but doesn’t wait for an RH change? Does Cumulus have faster update intervals than the VP2 console? I think I once saw someone say here that you can get temperature in tenths resolution with temp/hum stations using it?
I may of said that wrong the DP changes with temperature every update couple seconds sometimes, because both are in tenths, Rh is changing less often.Ah okay. I get that with weatherlink. But therein lies the problem. If the RH holds at say 74% for me in a 1-min update, my temp can fluctuate 1-2F during the course of that minute and the dewpoint follows it given the "frozen" RH value.
I may of said that wrong the DP changes with temperature every update couple seconds sometimes, because both are in tenths, Rh is changing less often.Ah okay. I get that with weatherlink. But therein lies the problem. If the RH holds at say 74% for me in a 1-min update, my temp can fluctuate 1-2F during the course of that minute and the dewpoint follows it given the "frozen" RH value.
What I would like to do is keep my 75 in the FARS for temp, but use a Davis 31 in a 2nd temp/hum station with my old 7714 shield. Then I would take the temp from my FARS/75 and dew from the passive/31 to calculate RH and post to my site/CWOP. I think I saw that idea mentioned here before and that Cumulus would report 2nd temp readings in tenths. Basically it would be like an ASOS setup...FARS for temp and then a separate passive shield for the dewpoint.
Scratch that. It's meteobridge/meteohub.I may of said that wrong the DP changes with temperature every update couple seconds sometimes, because both are in tenths, Rh is changing less often.Ah okay. I get that with weatherlink. But therein lies the problem. If the RH holds at say 74% for me in a 1-min update, my temp can fluctuate 1-2F during the course of that minute and the dewpoint follows it given the "frozen" RH value.
What I would like to do is keep my 75 in the FARS for temp, but use a Davis 31 in a 2nd temp/hum station with my old 7714 shield. Then I would take the temp from my FARS/75 and dew from the passive/31 to calculate RH and post to my site/CWOP. I think I saw that idea mentioned here before and that Cumulus would report 2nd temp readings in tenths. Basically it would be like an ASOS setup...FARS for temp and then a separate passive shield for the dewpoint.
Interesting. I didn't realize Cumulus could do that.
Well eating crow today, in fact several of us because we were convinced the ASOS at KVTN was off. Council member/ Coop manager here in Valentine got permission to check ASOS ourselves and the unexpected happened. It was running it's usual +2°F above my station and coop so as drove out there was thinking "we have them now proof and will take pictures for evidence".
Took the certified thermometer out up and stuck probe into vaisala shield intake and and to my #-o was dead on. Spent 20 minutes waiting for any discrepancy and it was matching 5 minute average updates every time meanwhile in town it was 2° cooler still.
No conspiracy theory it's just warmer at airport. +2°
Icing last winter probably just didn't occur at airport.
I feel better knowing. I mentioned we may have a reverse of heat island going on because of intown foliage and vegetation.
In short, life is good again!
You didn't compare any dews while you were there???????????
I would be suprised if it was a continuous 2 degree discrepancy. Even with well stirred air?
Also looks like a lot of metal around the sensor shield, could this effect the readings? Not trying to be negative, just my curiosity and observation.
It would be nice if you could place a remote setup next to the the ASOS for a few weeks just to see if any of discrepancies occur. Good luck with that idea.
Yeah...I think they generally run 1.5-2m so that would be a little low.It would be nice if you could place a remote setup next to the the ASOS for a few weeks just to see if any of discrepancies occur. Good luck with that idea.
We may be doing a full day long test soon, just record high and low with portable certified thermometer. At least can see if the temperature spikes are real. Spot checking you may miss a issue because temps took off late 5:30-6:30 pm. One thing I noticed the air intake for blower seems rather low to ground, estimate about 4.3'. Lower than my FARS intakes at home 5.0'. I always thought between 5-6' was standard.
Next time I go out there I'll tape measure the intake.
It would be nice if you could place a remote setup next to the the ASOS for a few weeks just to see if any of discrepancies occur. Good luck with that idea.
We may be doing a full day long test soon, just record high and low with portable certified thermometer. At least can see if the temperature spikes are real. Spot checking you may miss a issue because temps took off late 5:30-6:30 pm. One thing I noticed the air intake for blower seems rather low to ground, estimate about 4.3'. Lower than my FARS intakes at home 5.0'. I always thought between 5-6' was standard.
Next time I go out there I'll tape measure the intake.
No explanation on low temperature difference.If I missed this from earlier, I apologize, but is your probe inside the aspirated chamber while testing?
Was pretty sure they did. My old 67CFM doesn't look so bad now, does it? :-PThis sucker is really pulling some air.No explanation on low temperature difference.If I missed this from earlier, I apologize, but is your probe inside the aspirated chamber while testing?
I thought I’d share my experience here, this topic confirms my long-held suspicions of wet bias with Davis sensors (not just the SHT31). I've not read the entire thing though.
I'm in the UK, in a valley, where on many nights the humidity rises above 95% with radiation mist/fog quite common. My set up is a 24h FARS and an older passive ISS, running two SHT31 sensors (18 and 24 months old)
These two sensors both drifted at the top end within 6 months (and in opposite directions for a while), The first went from reaching 98-99% maximum to only 95-96% (thick fog). I thought it may be a dodgy sensor so bought the 2nd sensor, but that also drifted down while by summer 2017 the first sensor was back to reaching 98-99% lol.
Currently, they reach about 97-98%, with the 2nd sensor 1-2% wetter through the mid-range.
Concerning the mid-range, and yep.. they seem to have a wet bias. I upload to a website that allows an easy comparison between two stations. This is me compared to the nearby official Met Office station (5 miles away) yesterday (a cooler, fresher day than many this summer with a well-mixed environment until about 9pm).
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My dew point is typically 2-3C higher (x1.8 for difference in F) Of course these are only hourly observation points so brief fluctuations could skew the graph, however this is a typical story.
Humidity for August so far
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As you can see I'm usually approaching 10% more humid. We are at virtually the same elevation with similar surroundings and I can’t see any genuine reasons for this when the wind is in the direction that it was yesterday. It does seem with me at least the problem is not just with warm humid airmasses.
Not happy with that but what can I do.. I don't really have a controlled environment to recondition sensors (and if they have to be removed from the Davis board? that's a no-go for me anyway).
Nearby Davis stations do read similar to me but probably have the same issue.
Also, a brief history of the previous sensors I've used in case it's of interest:
My 1st SHT11 failed in August 2009, I think it had less of a wet bias, but only reached 95-96%.
The 2nd SHT11 had a significant wet bias in the mid-range, and reached 98-99%.
I had a SHT75 'Davis ready' sensor from a seller on Ebay. That possibly had little bias but it only reached about 95% so think I only used it in the old/backup ISS.
I also had a SHT15 (3rd party), and it reached 97-98%. It still had some degree of wet-bias.
So as you can see wet biased mid-range and no 100% readings seems to have been a general theme for me.
I still have the 15 and 75 lying around so am going to plug them into my backup ISS and see what they say compared to the SHT31.
I still like the SHT31 for temperature and prefer its humidity response to the 11's I used. If a stable 'corrected' sensor came out I'd buy that, although my records won't be consistent but they aren't anyway with those sensor changes and drift lol.
Are you using the 75 without a filter?Yup. Used the 31 without a filter too.
Just a warning for those planning to mount a 75 using the wire-to-board connector. Those things are flimsy crap. I got it working on my 4th try (after burning through 3 other connectors). I then moved the sensor, and it wouldn't read correctly after that.
For those wondering, yes, the wires were in there properly (you could pull on them and they wouldn't come out). The wire end of the connector was as seated as you could make it, but it always kinda moves, no matter what.
Even if I could seal it when it was connected properly, I have no confidence that connector would last long term.
I know dendrite got it working and that's great. I guess I'm saying I'm not sure how easily that success can be replicated.
Caveat emptor. YMMV.
Don't know if anyone else has tried compensating by dialing in what humidity you want, but six days ago I dropped mine 2%. Since then I've been between 11 and 91%, 109 and 70°F, and have been tickled with the results. Of course I'm completely aware that this is certainly no fix and haven't "challenged" the upper and lower limit to boot, but in between, I'm very pleased. At least it's better than a sharp stick in the eye til there's a fix.
I have experience soldering... just not in such tight spaces. So I spread the leads apart vertically to give myself extra space.Sensirion doesn't recommend soldering to the 75 leads. These are the ones they recommend on the data sheet.
Well... after shorting the leads with excess solder, I attempted to "fix" my mess and the sensor became too hot to touch. It's pretty fubar'd now.
And with that I'm out of the 75 project.
To those who plan to proceed, you will need good soldering skills/tools, a well-lit workspace, and some way to safely immobilize the sensor.
For the average VP2 owner who just wants accurate humidity readings, the wait continues for a viable solution.
Yeah, figured as much since "only" 2% was needed for me to get in line.Don't know if anyone else has tried compensating by dialing in what humidity you want, but six days ago I dropped mine 2%. Since then I've been between 11 and 91%, 109 and 70°F, and have been tickled with the results. Of course I'm completely aware that this is certainly no fix and haven't "challenged" the upper and lower limit to boot, but in between, I'm very pleased. At least it's better than a sharp stick in the eye til there's a fix.
Not really an option for most. Many have sensors that struggle to reach 98% with half stopping at 96% even in soupy fog so dialing back what most need around 6-8% (not 2%) would really look worse on foggy mornings and you are reporting 88-90% humidity.
If you give it a shot...Just a warning for those planning to mount a 75 using the wire-to-board connector. Those things are flimsy crap. I got it working on my 4th try (after burning through 3 other connectors). I then moved the sensor, and it wouldn't read correctly after that.
For those wondering, yes, the wires were in there properly (you could pull on them and they wouldn't come out). The wire end of the connector was as seated as you could make it, but it always kinda moves, no matter what.
Even if I could seal it when it was connected properly, I have no confidence that connector would last long term.
I know dendrite got it working and that's great. I guess I'm saying I'm not sure how easily that success can be replicated.
Caveat emptor. YMMV.
This sounds like fun. Not! I think I ordered 6 for 2 sensors. Is the issue with the wire (plug) side or sensor? If on wire side I may be able to solder a better connection.
If you give it a shot...Just a warning for those planning to mount a 75 using the wire-to-board connector. Those things are flimsy crap. I got it working on my 4th try (after burning through 3 other connectors). I then moved the sensor, and it wouldn't read correctly after that.
For those wondering, yes, the wires were in there properly (you could pull on them and they wouldn't come out). The wire end of the connector was as seated as you could make it, but it always kinda moves, no matter what.
Even if I could seal it when it was connected properly, I have no confidence that connector would last long term.
I know dendrite got it working and that's great. I guess I'm saying I'm not sure how easily that success can be replicated.
Caveat emptor. YMMV.
This sounds like fun. Not! I think I ordered 6 for 2 sensors. Is the issue with the wire (plug) side or sensor? If on wire side I may be able to solder a better connection.
Notice how the connector opens and closes. Use a little flat head precision screwdriver to gently open it all the way. There will be a subtle "click" into the fully open position. Cut the wires straight across, line them up, and insert them. They will freely and loosely go in to a certain point. Then you need to give them some extra force to push them through all the way to make the connection.
The next part is where they tend to break. When closing the connector over the wires, do it gently with even pressure. I don't recommend trying to close it all the way as there are multiple locations where the plastic can break apart. I found that out twice. Heck, just closing it with your thumb and index finger may be enough.
I have experience soldering... just not in such tight spaces. So I spread the leads apart vertically to give myself extra space.
Well... after shorting the leads with excess solder, I attempted to "fix" my mess and the sensor became too hot to touch. It's pretty fubar'd now.
And with that I'm out of the 75 project.
To those who plan to proceed, you will need good soldering skills/tools, a well-lit workspace, and some way to safely immobilize the sensor.
For the average VP2 owner who just wants accurate humidity readings, the wait continues for a viable solution.
I have experience soldering... just not in such tight spaces. So I spread the leads apart vertically to give myself extra space.
Well... after shorting the leads with excess solder, I attempted to "fix" my mess and the sensor became too hot to touch. It's pretty fubar'd now.
And with that I'm out of the 75 project.
To those who plan to proceed, you will need good soldering skills/tools, a well-lit workspace, and some way to safely immobilize the sensor.
For the average VP2 owner who just wants accurate humidity readings, the wait continues for a viable solution.
There are female pin connectors that you can solder instead of the actual sensor. You can find them at mouser or newark 14.
Also I made a bonehead mistake of not mentioning I do use the humidity offset feature on weather display then add back in the offset on the high-end to reach 100%.
The raw readings on my 75 reach 98 tops.
I have experience soldering... just not in such tight spaces. So I spread the leads apart vertically to give myself extra space.
Well... after shorting the leads with excess solder, I attempted to "fix" my mess and the sensor became too hot to touch. It's pretty fubar'd now.
And with that I'm out of the 75 project.
To those who plan to proceed, you will need good soldering skills/tools, a well-lit workspace, and some way to safely immobilize the sensor.
For the average VP2 owner who just wants accurate humidity readings, the wait continues for a viable solution.
There are female pin connectors that you can solder instead of the actual sensor. You can find them at mouser or newark 14.
Also I made a bonehead mistake of not mentioning I do use the humidity offset feature on weather display then add back in the offset on the high-end to reach 100%.
The raw readings on my 75 reach 98 tops.
I have experience soldering... just not in such tight spaces. So I spread the leads apart vertically to give myself extra space.
Well... after shorting the leads with excess solder, I attempted to "fix" my mess and the sensor became too hot to touch. It's pretty fubar'd now.
And with that I'm out of the 75 project.
To those who plan to proceed, you will need good soldering skills/tools, a well-lit workspace, and some way to safely immobilize the sensor.
For the average VP2 owner who just wants accurate humidity readings, the wait continues for a viable solution.
There are female pin connectors that you can solder instead of the actual sensor. You can find them at mouser or newark 14.
Also I made a bonehead mistake of not mentioning I do use the humidity offset feature on weather display then add back in the offset on the high-end to reach 100%.
The raw readings on my 75 reach 98 tops.
So that’s why your DPs is matching up well with the nearby airport stations?
BTW: I sent you a PM
It would be nice if Davis offered this as a fix. HINT
Yes and I would think it would not be too hard to add some kind of adjustment slope in a firmware update. Of coarse if they were to do that they would be admitting that there is a problem.
Well the wiring in my 75 seems to have developed a short somewhere so i switched it out with a new 31 I have had lying around in a stock Davis filter. Switched it out yesterday and was surprised to see it reach 100% last night with ease. We did have a heavy shower come through yesterday around sunset that put down about 1/3 of an inch followed by partly cloudy skies last night with some light fog this morning. I guess I will leave it in there for a few days to see how it tracks along with surrounding ASOS stations and to see if a substantial wet bias develops. Still using the MeteoShield Pro for those of you wondering.
Well the wiring in my 75 seems to have developed a short somewhere so i switched it out with a new 31 I have had lying around in a stock Davis filter. Switched it out yesterday and was surprised to see it reach 100% last night with ease. We did have a heavy shower come through yesterday around sunset that put down about 1/3 of an inch followed by partly cloudy skies last night with some light fog this morning. I guess I will leave it in there for a few days to see how it tracks along with surrounding ASOS stations and to see if a substantial wet bias develops. Still using the MeteoShield Pro for those of you wondering.I had problems with moisture on the PCB with my first SHT75 until I put the silicone conformal coating on it. Now only the sensor and tip of the PCB that the sensor sits on is exposed.
Well the wiring in my 75 seems to have developed a short somewhere so i switched it out with a new 31 I have had lying around in a stock Davis filter. Switched it out yesterday and was surprised to see it reach 100% last night with ease. We did have a heavy shower come through yesterday around sunset that put down about 1/3 of an inch followed by partly cloudy skies last night with some light fog this morning. I guess I will leave it in there for a few days to see how it tracks along with surrounding ASOS stations and to see if a substantial wet bias develops. Still using the MeteoShield Pro for those of you wondering.I had problems with moisture on the PCB with my first SHT75 until I put the silicone conformal coating on it. Now only the sensor and tip of the PCB that the sensor sits on is exposed.
I've been sitting at 97-98% with 1.60" of rain in 24hrs and mine is still running fine.
Speaking of soldering, I found these pin connectors on Mouser made by Mill Max. They come with solder cups where it looks as though you can insert the wire then solder it in. If it is as it looks this would be much easier for some of you who have bad luck trying to solder the 1.27mm tabs. I have left the link below.
https://www.mouser.com/ProductDetail/Mill-Max/851-13-004-10-003000?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJsOvP78LpBImemlioZUsStg%3d%3d
Speaking of soldering, I found these pin connectors on Mouser made by Mill Max. They come with solder cups where it looks as though you can insert the wire then solder it in. If it is as it looks this would be much easier for some of you who have bad luck trying to solder the 1.27mm tabs. I have left the link below.
https://www.mouser.com/ProductDetail/Mill-Max/851-13-004-10-003000?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJsOvP78LpBImemlioZUsStg%3d%3d
I'll try these. So stick wires in solder then the SHT75 plus in, is that the idea?
How are these sht75's working if interface is I2c? Thought that wouldn't work.
https://www.mouser.com/ProductDetail/Sensirion/SHT75?qs=%2fha2pyFaduhV3NYEe1MP5y%2fYDjvd38ndllSCUE15w5k%3d
How are these sht75's working if interface is I2c? Thought that wouldn't work.
https://www.mouser.com/ProductDetail/Sensirion/SHT75?qs=%2fha2pyFaduhV3NYEe1MP5y%2fYDjvd38ndllSCUE15w5k%3d
OK, after looking at a bunch of Rainwise stations, I should back up and say I only occasionally see the wet bias problem.
Whereas with Davis VP2s, well, it's uncommon to find one that's accurate in the middle range of humidity (40-70%).
Also, to be fair, the Acurite Atlases listed on Wunderground may very well be other stations at this point since the "beta" test period ended, I believe, and the product has yet to be released.
The Rainwise III uses the SHT15. I don't think they use separate temp & humidity sensors, although someone correct me if I'm wrong.
OK, after looking at a bunch of Rainwise stations, I should back up and say I only occasionally see the wet bias problem.
Whereas with Davis VP2s, well, it's uncommon to find one that's accurate in the middle range of humidity (40-70%).
Also, to be fair, the Acurite Atlases listed on Wunderground may very well be other stations at this point since the "beta" test period ended, I believe, and the product has yet to be released.
Do we know for sure that Rainwise uses Sensirion? Maybe just for humidity? I noticed their specs for temp go down to -67F and I have tried to research online what they use for temp and humidity, but came up without much info.
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxK
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
dendrite are there no worries about contamination using silicone conformal coating?
Maybe Onset hasn't figured it out? Because a quick check of one of their stations in Bryn Mawr (https://www.wunderground.com/personal-weather-station/dashboard?ID=KPAHAVER17#history (https://www.wunderground.com/personal-weather-station/dashboard?ID=KPAHAVER17#history)) shows a dew point of 72/73 when all the surrounding airports are reporting 70.
The more I observe other Sensirion sensors in other branded weather stations, the more I realize the problem isn't limited to Davis. I also see the problem in Atlas Elites and RainWise stations.
It probably goes back to what Ron (kcidwx) said about Sensirion sensors being designed for indoor use and HVAC primarily and not as meteorological instruments.
Doesn't seem like the cap matters, at least not for 11/15/31 sensors. Seems it's more about how often they've been in saturated air.
OK, after looking at a bunch of Rainwise stations, I should back up and say I only occasionally see the wet bias problem.
Whereas with Davis VP2s, well, it's uncommon to find one that's accurate in the middle range of humidity (40-70%).
Also, to be fair, the Acurite Atlases listed on Wunderground may very well be other stations at this point since the "beta" test period ended, I believe, and the product has yet to be released.
Do we know for sure that Rainwise uses Sensirion? Maybe just for humidity? I noticed their specs for temp go down to -67F and I have tried to research online what they use for temp and humidity, but came up without much info.
It looks like they may have changed sensor at sometime. The RWIII now says -40 to 60c range and use to be different like -68F. There was a forum member who lived in Alaska that would come here and brag about how his station would still work at those cold temperatures. https://www.rainwise.com/products/attachments/6801/20150710121434.pdf
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxK
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
So basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
The nearby airports (mainly philly international) have a weird dry bias that doesn’t make sense.
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxKSo basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
Anybody else notice that the 'dewpoint accuracy' graph at the bottom of page 4 [ https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf ] shows a VERY interesting anomaly: the dp 'error' suddenly kinks UPWARD at and above 90%RH.Most of them do it. They have the 31 at a steady 2% through the full range, but my hunch is it's a little higher than that in that 80/90-100% range. I mean, why would the 30 and 35 have a decrease in accuracy in high RH and not the 31?
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxKSo basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
My understanding the whole sensor fits inside waterproof case was idea. Davis encapsulates connections in plastic/rubber material on board.
Something needs to protect the connections or they won't last exposed to elements. May get by for awhile but eventually failure.
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxKSo basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
My understanding the whole sensor fits inside waterproof case was idea. Davis encapsulates connections in plastic/rubber material on board.
Something needs to protect the connections or they won't last exposed to elements. May get by for awhile but eventually failure.
Gotcha. Wonder if this casing would cause any lagging in responsiveness?
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxKSo basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
My understanding the whole sensor fits inside waterproof case was idea. Davis encapsulates connections in plastic/rubber material on board.
Something needs to protect the connections or they won't last exposed to elements. May get by for awhile but eventually failure.
Gotcha. Wonder if this casing would cause any lagging in responsiveness?
Won't know for awhile, but if Davis wants to get away from how they encapsulate on board (maybe damaging sensor) they should look into a waterproof design like this. This is how the probe sensors are designed in elongated tube fashion with waterproof enclosure. So we are just replicating that design with these.
I put the SF2 on my 31 about a week ago and have seen no difference. I would think the SF1 is similar.Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxKSo basically the SF1 filter caps are not able to protect the sensor during extreme humid conditions?
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
My understanding the whole sensor fits inside waterproof case was idea. Davis encapsulates connections in plastic/rubber material on board.
Something needs to protect the connections or they won't last exposed to elements. May get by for awhile but eventually failure.
Gotcha. Wonder if this casing would cause any lagging in responsiveness?
I think you'll find it's an option rather than a separate part, digi-key shows SHt31's with it installed https://www.digikey.com/products/en/sensors-transducers/humidity-moisture-sensors/529?k=sht31Thanks for the link. Yes, that's my point, you get the sensor and the cover and Davis has nothing to do with it. I can only hope that digi-key's handling process is as Sensirion dictates.
Are we sure these work with Davis ISS? I was under impression Davis had special protocol it's digital LLC.This is waaaay over my pay grade, but all I see is SHT31 and i2c thinking this is compatible. Merely an assumption.
Are we sure these work with Davis ISS? I was under impression Davis had special protocol it's digital LLC.This is waaaay over my pay grade, but all I see is SHT31 and i2c thinking this is compatible. Merely an assumption.
Time for those in the know....
Like I said... If no one else can give an absolute whether this will work or not, I'll be calling digi key tomorrow for their input, they may be clueless too.Are we sure these work with Davis ISS? I was under impression Davis had special protocol it's digital LLC.This is waaaay over my pay grade, but all I see is SHT31 and i2c thinking this is compatible. Merely an assumption.
Time for those in the know....
I2c is not for sure.
It will not work it has to be the sht31LS which is a sensibus format digital chipOf course it is... ](*,)
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?If Apple bought out Davis we'd have a new VP every year. ;)
As an aside, despite our problems with Davis, I am amazed at the VP2 product line. Today, I was installing a separate transmitter for my anemometer (part no. 6332) as I only get one decent wind reading from my 3 VP2s, so I consolidated to use only the one decent one. So I have used 4 of the available stations! Maybe a neighbor will take the remaining 4 transmitting stations? Considering the VP2 product line is now about 15 years old, I am amazed how it has stood the test of time with a few glitches along the way, including the SHT31.
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?If Apple bought out Davis we'd have a new VP every year. ;)
As an aside, despite our problems with Davis, I am amazed at the VP2 product line. Today, I was installing a separate transmitter for my anemometer (part no. 6332) as I only get one decent wind reading from my 3 VP2s, so I consolidated to use only the one decent one. So I have used 4 of the available stations! Maybe a neighbor will take the remaining 4 transmitting stations? Considering the VP2 product line is now about 15 years old, I am amazed how it has stood the test of time with a few glitches along the way, including the SHT31.
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?If Apple bought out Davis we'd have a new VP every year. ;)
As an aside, despite our problems with Davis, I am amazed at the VP2 product line. Today, I was installing a separate transmitter for my anemometer (part no. 6332) as I only get one decent wind reading from my 3 VP2s, so I consolidated to use only the one decent one. So I have used 4 of the available stations! Maybe a neighbor will take the remaining 4 transmitting stations? Considering the VP2 product line is now about 15 years old, I am amazed how it has stood the test of time with a few glitches along the way, including the SHT31.
Yeah and the price would double!
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
Unfortunately, CW2274, I think you are right. But if this SHT31 issue becomes the impetus for the long awaited VP3 or whatever Davis calls it, so be it. I will just have to update my equipment—unlike my cellphone—I still use an iPhone 5S! How embarrassing!
Just because it's popular sure as hell doesn't make it good. For me personally, I would never go downhill on my PWS, bad humidity 31 or not. I wonder how many WS's I would have needed to replace in the 11 years I've had my lone VP2 in this Arizona sun. Phftt, forget everything else in the VP2's favor, that's gravy.Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
- WS-2902A hit #1 in sales group on Amazon a few weeks back and is currently at #3 or #4.
[ducks and covers]
:roll:
Just because it's popular sure as hell doesn't make it good. For me personally, I would never go downhill on my PWS, bad humidity 31 or not. I wonder how many WS's I would have needed to replace in the 11 years I've had my lone VP2 in this Arizona sun. Phftt, forget everything else in the VP2's favor, that's gravy.Valentine Weather, several hundred posts ago, thought we had exhausted the points in this thread and should wait for a response from Davis. Well, I think this thread continues with great thought, but has anybody heard from Davis on the SHT31 issue?IMHO, there's no way that Davis will respond to this issue within the VP2's production lifetime. We (this forum) are a TINY portion of their sales and the other 99% are oblivious, just as we were until recent. Too much time, R&D is needed to address this issue properly to the satisfaction of us and Davis (read money). Honestly, I only see a resolution when a new model is released, and that's only IF Davis thinks it's a problem in the first place, which I'm dubious.
- WS-2902A hit #1 in sales group on Amazon a few weeks back and is currently at #3 or #4.
[ducks and covers]
:roll:
Obs from the Persian Gulf. A little off topic I know but I seriously wonder if there are any Davis VP2s around here and how they compare to official obs. I just cant imagine a dew point in the 90's with a HI of 140! My old boss who was a Weather Officer with the Navy back in the 70's used to tell me about the insane inversions they get there and how it made tacking aircraft with radar very difficult.This is an Ambient
(http://i1283.photobucket.com/albums/a541/hwcorder/persiangulfobs_zpsqy34pd0w.png) (http://s1283.photobucket.com/user/hwcorder/media/persiangulfobs_zpsqy34pd0w.png.html)
High end humidity update. I've had my VP2 for 2.5 months now. The SHT31 seems to be performing great. I regularly hit 99% humidity and this morning was stuck at 99% for 5 straight hours (no calibration adjustments made at all). https://www.wunderground.com/personal-weather-station/dashboard?ID=KPABRYNM2#history/tdata/s20180814/e20180814/mdailyI've always noticed mine starts losing the ability to reach upper RH values after the first warm season. Come the following May, 99-100% becomes a max of 97-98%.
There might be a slight wet bias in the mid ranges, but not much. Perhaps I just got lucky received a "good" temp/hum sensor. We shall see if I can continue to hit 99% in the coming months.
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Ended up using the connector I was originally going to use.
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Is that data available online?
Here they are. The post are a little more flexible that the other ones so you can spread the pins out some. Not too much though.Ended up using the connector I was originally going to use.
Which one was that?
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Is that data available online?
Thanks! Yes I upload to Wunderground and CWOP.
https://www.wunderground.com/personal-weather-station/dashboard?ID=KNCBELMO18#history
https://weather.gladstonefamily.net/site/D5686Here they are. The post are a little more flexible that the other ones so you can spread the pins out some. Not too much though.Ended up using the connector I was originally going to use.
Which one was that?
https://www.mouser.com/ProductDetail/Harwin/M50-3030442?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJmuuS%252b8ZjnXtI6OeGFBMW0g%3d%3d
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Is that data available online?
Thanks! Yes I upload to Wunderground and CWOP.
https://www.wunderground.com/personal-weather-station/dashboard?ID=KNCBELMO18#history
https://weather.gladstonefamily.net/site/D5686Here they are. The post are a little more flexible that the other ones so you can spread the pins out some. Not too much though.Ended up using the connector I was originally going to use.
Which one was that?
https://www.mouser.com/ProductDetail/Harwin/M50-3030442?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJmuuS%252b8ZjnXtI6OeGFBMW0g%3d%3d
How does the raw readings of the 75 humidity sensor compares to the airport? Why I ask is that you have done some offset stuff on WD.
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Is that data available online?
Thanks! Yes I upload to Wunderground and CWOP.
https://www.wunderground.com/personal-weather-station/dashboard?ID=KNCBELMO18#history
https://weather.gladstonefamily.net/site/D5686Here they are. The post are a little more flexible that the other ones so you can spread the pins out some. Not too much though.Ended up using the connector I was originally going to use.
Which one was that?
https://www.mouser.com/ProductDetail/Harwin/M50-3030442?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJmuuS%252b8ZjnXtI6OeGFBMW0g%3d%3d
How does the raw readings of the 75 humidity sensor compares to the airport? Why I ask is that you have done some offset stuff on WD.
The way I have it done on WD the adjusted readings and the raw readings from the sht75 are the same. But in the high end the raw readings only will reach 97-98% my adjusted reading will go to 100%. I guess the short answer would be it tracks pretty darn close to local ASOS stations.
Edit: When I say the adjusted and raw readings are the same I meant through the mid ranges <75%.
Jealous of that temperature, i got 78 degrees this am heading up to upper 90's today.
So I completed and installed my DIY probe made out of a Pilot Pin. Obviously the hardest part is getting the wires connected to socket the connector. I can tell you that those solder cup connectors I ordered from Mouser where no easier to work with and seemed more fragile. Ended up using the connector I was originally going to use. After a lot of patience I protected the connections with 4 very small heat sink wraps for each of the 4 wires and then covered that one with a larger wrap that covered the shielded part of the cable to the body of the connector itself. I then fit the connector through a slot in a piece of pcb board which of cut and shaved into a round piece that would fit into the body of the pin. All of this was done using a Dremel Tool. This was all sealed and weatherproofed with hot glue.Nice. I like the creativity there. If you had removed the clip from the pen I would've thought it was meant for holding a temp probe. :grin:
Where the sht75 (and hopefully a future 35) plugs in, fits perfectly into an Viasala HMP60 filter housing. It does not screw in but the fit is quite snug and I doubt anything could get through. At first I was using the gel grip in the pin to further seal the filter and pin housing but noticed that it was generating static charge so I removed it. I think filter is very well sealed but I might wrap some electrical tape around it just to be sure. Here are some pics. I will say it will be very nice to be able to remove and replace the probe with ease into the MeteoShield Pro which I have decided to use at least for now.
Is that data available online?
Thanks! Yes I upload to Wunderground and CWOP.
https://www.wunderground.com/personal-weather-station/dashboard?ID=KNCBELMO18#history
https://weather.gladstonefamily.net/site/D5686Here they are. The post are a little more flexible that the other ones so you can spread the pins out some. Not too much though.Ended up using the connector I was originally going to use.
Which one was that?
https://www.mouser.com/ProductDetail/Harwin/M50-3030442?qs=sGAEpiMZZMs%252bGHln7q6pm8Vn94ktop%2fJmuuS%252b8ZjnXtI6OeGFBMW0g%3d%3d
How does the raw readings of the 75 humidity sensor compares to the airport? Why I ask is that you have done some offset stuff on WD.
The way I have it done on WD the adjusted readings and the raw readings from the sht75 are the same. But in the high end the raw readings only will reach 97-98% my adjusted reading will go to 100%. I guess the short answer would be it tracks pretty darn close to local ASOS stations.
Edit: When I say the adjusted and raw readings are the same I meant through the mid ranges <75%.
So how does it do over 75%? Wet or dry bias?
I would say it continues to do very well all the way up until the mid 90% range before the dry bias shows up. Sensor seems to peek at 98%.Yeah, I think Davis and Sensirion may be a little at fault here. My new 75 has no problem with 99%-100%, but my 5 y/o one maxes out at 96%. I assume the age of yours is somewhere in between and you're maxing at 98%.
I would say it continues to do very well all the way up until the mid 90% range before the dry bias shows up. Sensor seems to peek at 98%.Yeah, I think Davis and Sensirion may be a little at fault here. My new 75 has no problem with 99%-100%, but my 5 y/o one maxes out at 96%. I assume the age of yours is somewhere in between and you're maxing at 98%.
Like you, I find both do well during the day with lower RH.
Did you see what Jerry and I ordered? I have 2 on the way may not be here until fall however. https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=a2g0s.9042311.0.0.69af4c4dlQrpxK
Others have some like https://www.emesystems.com/sht75pg/documents/SHT75PG.pdf
dendrite are there no worries about contamination using silicone conformal coating?
Very thick, prolonged radiation fog this morning. The SHT75 has been at 99% for awhile with a low of 54.2F.
CON has been running 1/4-1/8SM visibility and alternating between a dewpoint depression of 0F and 1F. So with rounding, my hunch is that they're actually around 99% RH in reality. They had a low of 53F.
LCI is coming out of the fog now, but had a similar deal. Mostly 0F, but some 1F dewpoint depressions in the 5 minute obs...probably about 99% RH. They were also 1/8-1/4SM and had a low of 54F.
Very small and very responsive. My setup really is like the raw data from an ASOS. I may move my sensor up to a full 2m (6.5ft) to pull it away from the sfc heating as much as possible without going over the 2m mark (40 CFM fan remember). Either that or I'll put a 5 minute averaging algorithm on the data. For now I'm just accepting the raw readings for what they are. If I put my hand briefly under the air intake of the shield I see a spike in temperature in my data.Very thick, prolonged radiation fog this morning. The SHT75 has been at 99% for awhile with a low of 54.2F.
CON has been running 1/4-1/8SM visibility and alternating between a dewpoint depression of 0F and 1F. So with rounding, my hunch is that they're actually around 99% RH in reality. They had a low of 53F.
LCI is coming out of the fog now, but had a similar deal. Mostly 0F, but some 1F dewpoint depressions in the 5 minute obs...probably about 99% RH. They were also 1/8-1/4SM and had a low of 54F.
Awesome! I opened my package that has the 75 sensor in it and I didn’t realize how small that sensor really was. Lol
Very small and very responsive. My setup really is like the raw data from an ASOS. I may move my sensor up to a full 2m (6.5ft) to pull it away from the sfc heating as much as possible without going over the 2m mark (40 CFM fan remember). Either that or I'll put a 5 minute averaging algorithm on the data. For now I'm just accepting the raw readings for what they are. If I put my hand briefly under the air intake of the shield I see a spike in temperature in my data.Very thick, prolonged radiation fog this morning. The SHT75 has been at 99% for awhile with a low of 54.2F.
CON has been running 1/4-1/8SM visibility and alternating between a dewpoint depression of 0F and 1F. So with rounding, my hunch is that they're actually around 99% RH in reality. They had a low of 53F.
LCI is coming out of the fog now, but had a similar deal. Mostly 0F, but some 1F dewpoint depressions in the 5 minute obs...probably about 99% RH. They were also 1/8-1/4SM and had a low of 54F.
Awesome! I opened my package that has the 75 sensor in it and I didn’t realize how small that sensor really was. Lol
Well... it happened. Looks like my good 31 just went bad on humidity.
Well... it happened. Looks like my good 31 just went bad on humidity.
So that was what? Like 2 and a half weeks old? This is the new 31 in the 7714 right?
Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?
This QC blows, and frankly is unacceptable. ](*,)
Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?
This QC blows, and frankly is unacceptable. ](*,)
Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?
This QC blows, and frankly is unacceptable. ](*,)
It probably all boils down to how Davis mounts the 31 chip into the PCB. They should’ve done at least what RW does and others by making a temp/hum probe. But who knows. All I can say is that, as of now,
Oh, absolutely not! I even confirmed with Ryan that I could return this one if it sucks, read above :roll:, and I will. He's even RMA-ing all his bubble wrapped stuff back to Davis, although it doesn't seem to matter....I'll see if he'll let me buy three or so and see if I get lucky with one and return the others.Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?don't blame SI at all.
This QC blows, and frankly is unacceptable. ](*,)
Oh, absolutely not! I even confirmed with Ryan that I could return this one if it sucks, read above :roll:, and I will. He's even RMA-ing all his bubble wrapped stuff back to Davis, although it doesn't seem to matter....I'll see if he'll let me buy three or so and see if I get lucky with one and return the others.Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?don't blame SI at all.
This QC blows, and frankly is unacceptable. ](*,)
Maybe if we swamp Davis with 31 returns they'll get the picture a little more in focus. :-x
Oh, they're aware....Has anyone had any correspondence with Davis on this issue?Oh, absolutely not! I even confirmed with Ryan that I could return this one if it sucks, read above :roll:, and I will. He's even RMA-ing all his bubble wrapped stuff back to Davis, although it doesn't seem to matter....I'll see if he'll let me buy three or so and see if I get lucky with one and return the others.Welp, so much for that. I got another new 31 today from Ryan that was properly packaged, ie, no bubble wrap. As is, my 8 month old 31 in use has a 2% humidity subtraction for the wet bias, and does a very nice job there, for now. The new (properly packaged 31, have you), is even wetter at ~1.3F higher dew and ~2% higher humidity than the old 31 in use. I brought the ISS inside for testing to stabilize the data and found that the old, drier 31 tracts right in line (with the 2% subtraction) with SHT11 in my Vue, dew and humidity. Point being, the Vue's SHT11 looks spot on with no correction. Davis obviously assembles both, why does the console not have the wet bias?don't blame SI at all.
This QC blows, and frankly is unacceptable. ](*,)
Maybe if we swamp Davis with 31 returns they'll get the picture a little more in focus. :-x
...
Has anyone had any correspondence with Davis on this issue?
I'm pretty bummed out my 10+ year monitor 2 dewpoints track local weather service station while my just over a year old sht31 has gone out of calibration with dewpoints a few degrees higher usually.
I'm running a 75 right now (Thanks Jerry) and do see dp running lower around 2 degrees vs SHT31's . This removes any wet bias. Problem is when I did the damp rag test for 2 hours max was only 97%.Yeah...give it a little time. I've routinely been hitting 98-99% every night with the brief touching of 100% some days. Have you also seen a big difference in the temp response compared to the 31...especially during the day with better mixing?
I'm testing inside the PRO meteo shield along with a 31 and plan on doing this for few days and see what I get in the morning against the SHT31 in same shield. Also want to watch temperature. They run almost identical on temps so far in the 80-90° range.
Currently the 75 is very close to airport 1.3 mi away on DP 63° https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVTN&unit=0&timetype=LOCAL/
I'm running a 75 right now (Thanks Jerry) and do see dp running lower around 2 degrees vs SHT31's . This removes any wet bias. Problem is when I did the damp rag test for 2 hours max was only 97%.
I'm testing inside the PRO meteo shield along with a 31 and plan on doing this for few days and see what I get in the morning against the SHT31 in same shield. Also want to watch temperature. They run almost identical on temps so far in the 80-90° range.
Currently the 75 is very close to airport 1.3 mi away on DP 63° https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVTN&unit=0&timetype=LOCAL/
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Main sensor E3958 and website click on globe for live data is now the SHT75 with no offset for humidity like I had for the 31.
The other sensors are not online. I'm using envoy8x and the software it comes with WDTU which is capable of exporting to excel for graphs.
5 min update to cwop here:
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=E3958&unit=0&timetype=LOCAL
If you want to compare dp with airport here:
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVTN&unit=0&timetype=LOCAL/
Looks like you're running the usual 2F cooler than the ASOS, but you've been consistently 2F cooler on dewpoint as well. You were fairly well mixed overnight though. I'm interested to see how the daytime dewpoint track.
I noticed your MADIS data is consistently staggered 1hr from the analysis. What's up with that? It looks like MADIS is lagging 1hr behind your station. Is this some kind of CDT vs CST issue? It looks like your graphs would be fine if you set your clocks back an hour.
https://weather.gladstonefamily.net/site/E3958
Looks like you're running the usual 2F cooler than the ASOS, but you've been consistently 2F cooler on dewpoint as well. You were fairly well mixed overnight though. I'm interested to see how the daytime dewpoint track.
https://weather.gladstonefamily.net/site/E3958
Been keeping track of your DP readings Randy. Been impressed so far. Seems like it’s neck to neck with the ASOS. Sometimes it’s lower.
Did a chest freezer test on sht31 vs 75 this morning for anyone considering change over living in colder climate. Results unscientific with sensors tied together. Let freezer go through 3 cooling cycles so took over an hour. Temperature difference was either .5 or .6 with the SHT75 reading warmer.
As freezer warmed up the 75 would really leave the 31 behind (+3) before compressor started again. Then on cool down it rapidly made the 3 degree difference up catching the 31 within couple minutes of compressor kicking on. The 75 does adjust rapidly to temperature change.
Below zero
SHT75 -8.2 SHT31 -8.7
SHT75 -8.1 SHT31 -8.6
SHT75 -7.9 SHT31 -8.4
The specs in that range are around +/- 1.2C for the 75 and +/- 0.25 for the 31. So yeah, only a consistent 0.5F difference isn't too bad. Heck, maybe the 31 is -0.2C and the 75 is +0.3C.Did a chest freezer test on sht31 vs 75 this morning for anyone considering change over living in colder climate. Results unscientific with sensors tied together. Let freezer go through 3 cooling cycles so took over an hour. Temperature difference was either .5 or .6 with the SHT75 reading warmer.
As freezer warmed up the 75 would really leave the 31 behind (+3) before compressor started again. Then on cool down it rapidly made the 3 degree difference up catching the 31 within couple minutes of compressor kicking on. The 75 does adjust rapidly to temperature change.
Below zero
SHT75 -8.2 SHT31 -8.7
SHT75 -8.1 SHT31 -8.6
SHT75 -7.9 SHT31 -8.4
That’s not bad at all. Rarely if Alabama gets below zero but looks like the 75 isn’t a bad performer in that range. Wonder what your calibrated thermometer would’ve read?
I may have to run that test, my calibrated meter has a calibration point of -10 degrees and is right on calibration wise. I will have to try it when i get the new sensor out of the standard shield.
How well do they all match up at a warmer temp in the fridge?I may have to run that test, my calibrated meter has a calibration point of -10 degrees and is right on calibration wise. I will have to try it when i get the new sensor out of the standard shield.
Good deal Jerry.
I'm wondering about the 31 accuracy down low now.
Added the specs to certified thermometer I used above post.
How well do they all match up at a warmer temp in the fridge?I may have to run that test, my calibrated meter has a calibration point of -10 degrees and is right on calibration wise. I will have to try it when i get the new sensor out of the standard shield.
Good deal Jerry.
I'm wondering about the 31 accuracy down low now.
Added the specs to certified thermometer I used above post.
Interesting results, calibrated meter accuracy +/- .3F meter -3.4 31-3.7 75-2.4 15-1.4 so figuring the meter between -3.1 to -3.7 it looks like the 31 is the winner which i would have expected based on specs. the 75 is pretty close to specs for it, not good on low end. The 15 is much better in the south than the north lol.Nice work from you two guys. Now I anxiously await the pin 35 and an easy way to implement it with a VP2.
I was letting them cycle all the way to bottom and record where they turn. Can't trust between because some sensors drop faster then others.Yes. Even monitoring just one sensor I always wait for it to reverse course and go from there, then you're sure.
11 below Certified is running with the SHT31 also.
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Nice obs Randy. I'll probably get a new 31 and swap it out from the 75 before we start getting well below freezing. I still like the idea of the low thermal mass pin model, but I'll have to wait for the 35. rdsman is doing good work over in that other thread with reading the data from the 35.
Well it looks to me like none of the sensors like it cold :lol:. You need to move down here where freezing temps are a rarity. The meter has been steady on -3.9 and the 31 has been holding at -2.9 no better than the 75. It looks like in cold weather areas you need to cull out the sensors to find one like the first 31. Heck you get down to that temp what difference does a degree or to make anyway, cold is cold :lol:.
Man Randy if you consider -30 weather heaven then i think you brain froze at some point :lol:Took the words right outta my mouth, then I thought about the three or four days in a row last year I was over 116F and decided to :-$.
Yes IMO the7675 is solid performer where humidity plays a big role which happens to be where most people live because of man's attraction to water which was once needed for commerce and travel.
I don't think that was a temp comparison or that it had anything to do with temp accuracy. It's his attempt to convert the I2C to sensibus. He's trying to understand how the 75 is read and adapt the 35 to that. Basically he has it down to 0.0-0.1F and 0.0-0.1% RH. IOW, what the 75 would report as say 85.4F, the 35 would read it as 85.3F or 85.4F. So there is probably some 0.05F error in there which he is trying to fine tune. Personally, a 0.0-0.1F conversion error on top of the 0.1-0.2F sensor accuracy is good enough for me.
I don't think that was a temp comparison or that it had anything to do with temp accuracy. It's his attempt to convert the I2C to sensibus. He's trying to understand how the 75 is read and adapt the 35 to that. Basically he has it down to 0.0-0.1F and 0.0-0.1% RH. IOW, what the 75 would report as say 85.4F, the 35 would read it as 85.3F or 85.4F.
For those interested in the sht75 and may not have soldering skills or any luck with the crimping version, I've found this option. Haven't done this myself however so nothing confirmed.
The plug/cord was made for the sht75.... called 3M-CABLES FOR EK-H4 made for evaluation kit.
The plug is 3 meters and rather expensive at $80. You only need 1 however as the sensors go bad just replace the SHT75.
Looks like the connector on the stock plugs is the RJ12 which has 6 gold connectors. Only 4 will be used however. You will need to figure out which 4 go where for the sensor to work and crimp plug accordingly with tool.
I referenced this video about plugs on youtube to determine what was being used. The stock sht31 plug has 6 contacts the red and black are not connected to the SHT31 sensor.
Youtube video on plugs: https://www.youtube.com/watch?v=fjNCUDrdULw
Link to sht75 plug/cord sold by digikey: https://www.digikey.com/product-detail/en/sensirion-ag/3M-CABLES-FOR-EK-H4/1649-1055-ND/5982944
Anyone with more knowledge please chime in on this.
For those interested in the sht75 and may not have soldering skills or any luck with the crimping version, I've found this option. Haven't done this myself however so nothing confirmed.
The plug/cord was made for the sht75.... called 3M-CABLES FOR EK-H4 made for evaluation kit.
The plug is 3 meters and rather expensive at $80. You only need 1 however as the sensors go bad just replace the SHT75.
Looks like the connector on the stock plugs is the RJ12 which has 6 gold connectors. Only 4 will be used however. You will need to figure out which 4 go where for the sensor to work and crimp plug accordingly with tool.
I referenced this video about plugs on youtube to determine what was being used. The stock sht31 plug has 6 contacts the red and black are not connected to the SHT31 sensor.
Youtube video on plugs: https://www.youtube.com/watch?v=fjNCUDrdULw
Link to sht75 plug/cord sold by digikey: https://www.digikey.com/product-detail/en/sensirion-ag/3M-CABLES-FOR-EK-H4/1649-1055-ND/5982944
Anyone with more knowledge please chime in on this.
According to the datasheet (https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/Humidity/Sensirion_Humidity_Sensors_EK-H4_Datasheet.pdf (https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/Humidity/Sensirion_Humidity_Sensors_EK-H4_Datasheet.pdf)), the cable terminates in an RJ45 jack. So you would need to chop that off and splice it into the end of a 31/15/11 sensor cable or the like.
Also might want to put some conformal coating over the sensor end of the cable too to prevent water ingress.
For those interested in the sht75 and may not have soldering skills or any luck with the crimping version, I've found this option. Haven't done this myself however so nothing confirmed.
The plug/cord was made for the sht75.... called 3M-CABLES FOR EK-H4 made for evaluation kit.
The plug is 3 meters and rather expensive at $80. You only need 1 however as the sensors go bad just replace the SHT75.
Looks like the connector on the stock plugs is the RJ12 which has 6 gold connectors. Only 4 will be used however. You will need to figure out which 4 go where for the sensor to work and crimp plug accordingly with tool.
I referenced this video about plugs on youtube to determine what was being used. The stock sht31 plug has 6 contacts the red and black are not connected to the SHT31 sensor.
Youtube video on plugs: https://www.youtube.com/watch?v=fjNCUDrdULw
Link to sht75 plug/cord sold by digikey: https://www.digikey.com/product-detail/en/sensirion-ag/3M-CABLES-FOR-EK-H4/1649-1055-ND/5982944
Anyone with more knowledge please chime in on this.
According to the datasheet (https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/Humidity/Sensirion_Humidity_Sensors_EK-H4_Datasheet.pdf (https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/Humidity/Sensirion_Humidity_Sensors_EK-H4_Datasheet.pdf)), the cable terminates in an RJ45 jack. So you would need to chop that off and splice it into the end of a 31/15/11 sensor cable or the like.
Also might want to put some conformal coating over the sensor end of the cable too to prevent water ingress.
So should work no problem with a crimping tool $13 and RJ12 jack?
Yesterday the SHT75 and 31 temperature were the same all day within .3F because wind speeds were up so humidity should have also followed and been the same. They weren't.Just saw this. I noticed your dewpoint charts on Gladstone are right in line and you've been running neck and neck generally with VTN.
This is graph shows humidity difference throughout day. As you can see morning and evening are the same but during critical time of day when temperatures go up the 75 runs in normal range vs the 31 averaging about 5% higher sometimes more sometimes less. DP averages about 2°F higher on 31 also.
Well i can not be sure but i think i just had a 75 fall victim to the fars, i had a new 75 running in the fars for comparison and it hit 99 a couple times but alas it now won't go over 95 percent sometimes bumps 96. We had several nights of light fog and the humidity was high for quite a while each night and now low humidity readings. I am going to try drying and hydrating it to see what happens.
Maybe i am just unlucky lol, i did put it in my tester and it maxed out at 95 so i am letting it dry in oven for most of the day and will try it again. Hope it comes alive again. It may just have been a bad sensor.
Well i can not be sure but i think i just had a 75 fall victim to the fars, i had a new 75 running in the fars for comparison and it hit 99 a couple times but alas it now won't go over 95 percent sometimes bumps 96. We had several nights of light fog and the humidity was high for quite a while each night and now low humidity readings. I am going to try drying and hydrating it to see what happens.
Maybe i am just unlucky lol, i did put it in my tester and it maxed out at 95 so i am letting it dry in oven for most of the day and will try it again. Hope it comes alive again. It may just have been a bad sensor.
Were you using the stock filter or something else?
Using the factory filter sf1.
It was in the standard Davis fars with stock fan.
For those interested in the sht75 and may not have soldering skills or any luck with the crimping version, I've found this option. Haven't done this myself however so nothing confirmed.
The plug/cord was made for the sht75.... called 3M-CABLES FOR EK-H4 made for evaluation kit.
The plug is 3 meters and rather expensive at $80. You only need 1 however as the sensors go bad just replace the SHT75.
Looks like the connector on the stock plugs is the RJ12 which has 6 gold connectors. Only 4 will be used however. You will need to figure out which 4 go where for the sensor to work and crimp plug accordingly with tool.
I referenced this video about plugs on youtube to determine what was being used. The stock sht31 plug has 6 contacts the red and black are not connected to the SHT31 sensor.
Youtube video on plugs: https://www.youtube.com/watch?v=fjNCUDrdULw
Link to sht75 plug/cord sold by digikey: https://www.digikey.com/product-detail/en/sensirion-ag/3M-CABLES-FOR-EK-H4/1649-1055-ND/5982944
Anyone with more knowledge please chime in on this.
Was it tested and working prior to sealing?
Sounds like the numbers I was getting so after I destroyed all connectors (5) gave up.
Valentine, I see where your 75 finally went up to 100%
Valentine, I see where your 75 finally went up to 100%
Actually it didn't, what you see is my SHT31 on FARS. Little disappointed in the 75's ability to go beyond 97% in passive shield.
I think it would make 98% in FARS however because there is zero wind not even whisper at ground level.
Dense fog this morning so should of been there. Truthfully these SHT75 are no better than the 31's it's a crap shoot whether sensor can reach even 98%. Where they are superior is the no high humidity bias but for cold climates inferior on temperature. Too bad we don't have a sensor that can do it all.
If sensor makes 98% Cumulus will display 100%. I have another 31 that goes to 100% every time at remote station inside a PRO shield also.
4 mornings in a row with 99/100% at my place. I guess YMMV. Anyone test a psychrometer or the acurites in those 97/98% conditions?
Something different, have the SHT75 back in service but this time inside FARS. FARS sensor chamber is big enough for the skinny 75 and big 31 at same time. So should I feel a need to swap over to 31 it will be quick and easy.
Added extension on the 75 also so can reach TX1 easily without moving transmitters around.
From my experience with any of these sensors whether it be the sht 15, 75, or 31 if it doesn't have a wet bias in the low to mid RH it will usually not read above 98%. If it does reach the 99% to 100% it tends to read too wet a lower values. Very rare does it seem like I find a sensor that does both. My preference is to have better accuracy in the mid ranges than to have a sensor that reads 100%, but that"s just me.
Something different, have the SHT75 back in service but this time inside FARS. FARS sensor chamber is big enough for the skinny 75 and big 31 at same time. So should I feel a need to swap over to 31 it will be quick and easy.
Added extension on the 75 also so can reach TX1 easily without moving transmitters around.
Has anybody tried using a short 1-2 foot RJ45 male/female extension cable between the ISS and sensor to eliminate having to open the ISS each time while changing between sensors?
If yes, where did you get it from?
Something different, have the SHT75 back in service but this time inside FARS. FARS sensor chamber is big enough for the skinny 75 and big 31 at same time. So should I feel a need to swap over to 31 it will be quick and easy.
Added extension on the 75 also so can reach TX1 easily without moving transmitters around.
Has anybody tried using a short 1-2 foot RJ45 male/female extension cable between the ISS and sensor to eliminate having to open the ISS each time while changing between sensors?
If yes, where did you get it from?
Good Idea.
PIA feeding those cables inside ISS but I'm getting good at it now.. :-)
In my case I would need to protect the unused exposed connectors from elements. Same with any extension, couldn't leave exposed unless weather proofed with something likestickyTacky tape. Wrap in wax paper andstickyTacky tape works great on camera connectors also making everything waterproof. Reason I wrap in paper first it's much easier to get off and doesn't adhere to connections making a mess.
I had the sht31 30' cable going into fars shield already which reached TX1 primary ISS. Also needed a 30' cable for sht75 to reach so spliced in 4 wire flat cable I already had on hand. (Only takes 4 wires) for temperature sensor. Now won't need to keep jocking stuff around every time. \:D/
This stuff is messier than hell, but boy do it work.
https://www.amazon.com/Gardner-Bender-LTB-400-Electrical-Waterproof/dp/B000FPAN2K
I have decided to ask Ryan for a new SHT31 to replace the one in my new 24 hour fan VP2, not because of being wet, rather temperature inaccuracies at dawn.
temperature inaccuracies at dawn.:???: How is it only inaccurate at dawn?
This stuff is messier than hell, but boy do it work.
https://www.amazon.com/Gardner-Bender-LTB-400-Electrical-Waterproof/dp/B000FPAN2K
Yikes I don't like it. I prefer any of the the self fusing electrical tapes. Doesn't have to be scotch 70 others work just as well.
Had no idea this was meant to be in the "smelling range" of the sensor. Obviously not meant for that.This stuff is messier than hell, but boy do it work.
https://www.amazon.com/Gardner-Bender-LTB-400-Electrical-Waterproof/dp/B000FPAN2K
Yikes I don't like it. I prefer any of the the self fusing electrical tapes. Doesn't have to be scotch 70 others work just as well.
Yes, the "volatiles" are probably hell on the RH% sensor!
I actually use fusing tape before the liquid stuff. Just me I guess...This stuff is messier than hell, but boy do it work.
https://www.amazon.com/Gardner-Bender-LTB-400-Electrical-Waterproof/dp/B000FPAN2K
Yikes I don't like it. I prefer any of the the self fusing electrical tapes. Doesn't have to be scotch 70 others work just as well.
temperature inaccuracies at dawn.:???: How is it only inaccurate at dawn?
Even still..... :? Don't have an obstructed SF2 on the goofy one, do ya?temperature inaccuracies at dawn.:???: How is it only inaccurate at dawn?
My typo—should be dusk not dawn.
Even still..... :? Don't have an obstructed SF2 on the goofy one, do ya?temperature inaccuracies at dawn.:???: How is it only inaccurate at dawn?
My typo—should be dusk not dawn.
From my experience with any of these sensors whether it be the sht 15, 75, or 31 if it doesn't have a wet bias in the low to mid RH it will usually not read above 98%. If it does reach the 99% to 100% it tends to read too wet a lower values. Very rare does it seem like I find a sensor that does both. My preference is to have better accuracy in the mid ranges than to have a sensor that reads 100%, but that"s just me.
Huh? It doesn't even have an outdoor ISS, or whatever acurite calls it. How would you know?From my experience with any of these sensors whether it be the sht 15, 75, or 31 if it doesn't have a wet bias in the low to mid RH it will usually not read above 98%. If it does reach the 99% to 100% it tends to read too wet a lower values. Very rare does it seem like I find a sensor that does both. My preference is to have better accuracy in the mid ranges than to have a sensor that reads 100%, but that"s just me.
The Acurite unit I have (https://www.acurite.com/rain-gauge-station-lightning-detection-01021m.html) does not have the humidity problems like the Davis SHT sensors have.
Huh? It doesn't even have an outdoor ISS, or whatever acurite calls it. How would you know?From my experience with any of these sensors whether it be the sht 15, 75, or 31 if it doesn't have a wet bias in the low to mid RH it will usually not read above 98%. If it does reach the 99% to 100% it tends to read too wet a lower values. Very rare does it seem like I find a sensor that does both. My preference is to have better accuracy in the mid ranges than to have a sensor that reads 100%, but that"s just me.
The Acurite unit I have (https://www.acurite.com/rain-gauge-station-lightning-detection-01021m.html) does not have the humidity problems like the Davis SHT sensors have.
Rocking the 100% RH tonight. I haven't seen 100% this much since my analog sensor.Please forgive me, but after fifty pages of this thread, I've forgotten what you're "rocking" with, 75, 31, fan, no fan....
75 + 40CFM fan + no filterRocking the 100% RH tonight. I haven't seen 100% this much since my analog sensor.Please forgive me, but after fifty pages of this thread, I've forgotten what you're "rocking" with, 75, 31, fan, no fan....
Fine mist water droplets drawn onto sensor is making 100% much easier I'm sure. Sooner or later sensor will fail without any protection. This was what Jerry was experiencing in humid south Texas gulf region even using filter with FARS, killing sensors so decided to go with passive unit.I had my old 75 installed this way for an entire Fall-Winter-Spring period and didn't notice any changes in readings to the naked eye. A lot of you guys have 31s failing or drifting and that's with filters and passive/stock FARS shields. It hasn't been easy to hit 100%. It was mostly 99% with occasional obs of 100% and this was after almost 2" of synoptic rain followed by 12hrs of drizzle. The local METAR reported 0F to 1F dewpoint depressions too so RH was definitely in that 98-100% range at times.
You can replace the 75 at $20 each futureelectronics link was posted above by Jerry. I ordered a few replacements myself.
I had my old 75 installed this way for an entire Fall-Winter-Spring period and didn't notice any changes in readings to the naked eye. A lot of you guys have 31s failing or drifting and that's with filters and passive/stock FARS shields. It hasn't been easy to hit 100%. It was mostly 99% with occasional obs of 100% and this was after almost 2" of synoptic rain followed by 12hrs of drizzle. The local METAR reported 0F to 1F dewpoint depressions too so RH was definitely in that 98-100% range at times.
Sure seems strange that above 80% is not normal range and can cause an error.
what kind of sensor is this? How can a manufacturer make a humidity sensor that can't take humidity over 80% for several days, sure seems like some kind of poor planning to me. Could this be what is causing the error in the 31?
It could play a role, but I think it’s the way Davis mounts the 31 chip into the pcb. But I could be wrong.
I think the version of software on the console dictates whether it'll hit 0% or not.
It could play a role, but I think it’s the way Davis mounts the 31 chip into the pcb. But I could be wrong.
I wonder if Davis didn't ask for a different calibration for desert regions so it wasn't going to 0% humidity?
I've never heard that, the 15's had dry bias issue below 10%, remember? Has a change been made to compensate, causing the wet bias we now see. The Davis versions are different from the acurite 31 is why I was saying it may be a special calibration request. These 31's with LS protocol are specifically made for Davis and not publically available as far as I know or we would be purchasing instead of the 75's.
I think the version of software on the console dictates whether it'll hit 0% or not.
Hell Randy, I can't remember what was for dinner last night. Not saying the 15 didn't, I honestly don't recall.I've never heard that, the 15's had dry bias issue below 10%, remember?
I think the version of software on the console dictates whether it'll hit 0% or not.
Does anyone knows where you can get a crossover adapter for the RJ12? If I can get a RJ 12 adapter, then I won’t have to worry about getting rid of the 45 plug that’s on the EH-4 cable.The thing is you need the wires to line up (clk, vdd, gnd, data) according to the Davis ISS requirements.
Aight. Here is what my setup currently looks like. Keep in mind that the transmitter doesn’t read anything.
My RH dropped out to 0% this morning. The 31 is going back in when I get home. I wonder if water got into the connector.I would say sensor more likely or you would of lost everything if connector shorted.
Yeah who knows. My previous 75 never had an issue and made it through an entire winter. The sensor itself should've dried out yesterday with full sun and mid 80s.My RH dropped out to 0% this morning. The 31 is going back in when I get home. I wonder if water got into the connector.I would say sensor more likely or you would of lost everything if connector shorted.
Comparison of 75 and 31 in same stock Davis Fars shield at temperatures mid range this is the difference between the two sensors.
You may be right. I'm still at 97%-98% on all sensors 10am and may not drop out of 90's for another day or so, pushing that 60 hours of saturation before rain stops.
Has anyone else had spikes in temps and dew point in such a short amount of time like that?You definitely had some kind of boundary go through there based on the temp drop and consistent rise in dewpoint. Maybe the 78F is a little inflated, but you have a consistent 75F+ there. Was there any precip during that time even if very light? It looks like some kind of weak seabreeze given the E wind and the shift the a muggier southerly component.
See the loop at 20Z.Has anyone else had spikes in temps and dew point in such a short amount of time like that?You definitely had some kind of boundary go through there based on the temp drop and consistent rise in dewpoint.
See the loop at 20Z.Has anyone else had spikes in temps and dew point in such a short amount of time like that?You definitely had some kind of boundary go through there based on the temp drop and consistent rise in dewpoint.
https://weather.cod.edu/satrad/nexrad/index.php?type=LIX-N0Q-1-200
Honestly, I'm not sure, but if so, I'd be infrequent. It's certainly possible your sensor is acting up, obviously study it closely, you'll be the best judge as whether it's going out the door or not. I posted the radar loop because you could see a 'boundary' or 'outflow' at the time of your spike move from south to north, but the Gulfport airport did not show the spike, but that's only one observation per hour compared to yours every 5 minutes.See the loop at 20Z.Has anyone else had spikes in temps and dew point in such a short amount of time like that?You definitely had some kind of boundary go through there based on the temp drop and consistent rise in dewpoint.
https://weather.cod.edu/satrad/nexrad/index.php?type=LIX-N0Q-1-200
CW2274 you live out in the desert have you ever seen your humidity spike that much in such a short time with the monsoon or the influx of Pacific moisture?
All of mine reach 99% outside in the shields :grin: i don't see why yours don't unless you are just cursed :lol:.
All of mine reach 99% outside in the shields :grin: i don't see why yours don't unless you are just cursed :lol:.Mine also has no trouble reaching 99%
Well trying another 75. Did the damp rag test for about 2.5 hours it finally hit 98% went another hour and didn't go beyond. 4.5 hours total..
So I heated some water in big pot and gave sensor so hot steam humidity just a few minutes around 138° and saw 97% once. Took out cooled down to room temperature, 40% humidity.
Did the wet rag test again and it quickly reached 98% this time followed by 99% within 10 minutes total time where its still holding now for 15 minutes.
So my question do these sensors need broke-in?
As I was getting ready to post just noticed 100%....Hee haw \:D/
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As I was getting ready to post just noticed 100%....Hee haw \:D/Not to be Debbie Downer, but I just noticed your dew is higher than your temp. So, I guess the choice is 99%, or 100% with a 'technically' too high of a dew.
\As I was getting ready to post just noticed 100%....Hee haw \:D/Not to be Debbie Downer, but I just noticed your dew is higher than your temp. So, I guess the choice is 99%, or 100% with a 'technically' too high of a dew.
=D>\As I was getting ready to post just noticed 100%....Hee haw \:D/Not to be Debbie Downer, but I just noticed your dew is higher than your temp. So, I guess the choice is 99%, or 100% with a 'technically' too high of a dew.
It came together, dewpoint is calculated so it was slower posting. I've got 8 stations so the envoy8x is behind occasionally and wasn't there why I captured the image.
Could we trouble you to try a 31 also? :-)
IIRC, back when I picked up my 15, I called Sensirion and asked about all the 'conditioning' in their technical literature and if that was necessary, I basically got a "no", perhaps that was bad info. At this point, who knows. :roll:Could we trouble you to try a 31 also? :-)
Currently fresh out of 31's but worth a try. The way these measure humidity is resistance across a little bridge so maybe a little heat and steam loosens it up. Just a guess but seemed to work that time.
IIRC, back when I picked up my 15, I called Sensirion and asked about all the 'conditioning' in their technical literature and if that was necessary, I basically got a "no", perhaps that was bad info. At this point, who knows. :roll:Could we trouble you to try a 31 also? :-)
Currently fresh out of 31's but worth a try. The way these measure humidity is resistance across a little bridge so maybe a little heat and steam loosens it up. Just a guess but seemed to work that time.
heh...my 75s have always trumped the 31s on reaching the high end too. I'm not sure I've ever had a 31 over 98%.
Heads up for anyone wanting to change over to SHT75 and not great at soldering.
Digikey is about out of the Senserion cables 10' long with the 4 prong sht75 pin adapter. These need the RJ plug changed or splice in existing Davis RJ connector.
Jerry just did a couple up for another forum member and reported the 2-outside wires need swapped on RJ to work.
Reason I'm posting these cables are no longer being made and soon the SHT75 is also out of production.
Only place I've found the cables is Digikey with 6 left today. 3 weeks ago 70+ in stock so someone or ones, snagging them up.
https://www.digikey.com/product-detail/en/sensirion-ag/3M-CABLES-FOR-EK-H4/1649-1055-ND/5982944
I had a very wet period where the humidity was over 80 for several days and my sensor was showing about 2 higher, so i replaced it and after a day i put it back out this pm and it is tracking with the others, the 2 seems to be gone. All of the sensors have that caution warning about this quirk. At least it looks like it will clear up.
I had a very wet period where the humidity was over 80 for several days and my sensor was showing about 2 higher, so i replaced it and after a day i put it back out this pm and it is tracking with the others, the 2 seems to be gone. All of the sensors have that caution warning about this quirk. At least it looks like it will clear up.
Do you guys think it's possible that Davis has addressed and corrected the problem and haven't said anything (I truly don't think they'll ever admit a problem exists), or happenstance that 31's seem playing well more so with others?
Not positive, but I think the 31 wasn't even available then. I installed my first one late 3/16 and I believe that was pretty much hot off the press.Do you guys think it's possible that Davis has addressed and corrected the problem and haven't said anything (I truly don't think they'll ever admit a problem exists), or happenstance that 31's seem playing well more so with others?Don’t know...All I know is that the nearby station with the 31 is three years old. Sensor hasn’t been replaced.
Not positive, but I think the 31 wasn't even available then. I installed my first one late 3/16 and I believe that was pretty much hot off the press.Do you guys think it's possible that Davis has addressed and corrected the problem and haven't said anything (I truly don't think they'll ever admit a problem exists), or happenstance that 31's seem playing well more so with others?Don’t know...All I know is that the nearby station with the 31 is three years old. Sensor hasn’t been replaced.
Not positive, but I think the 31 wasn't even available then. I installed my first one late 3/16 and I believe that was pretty much hot off the press.Do you guys think it's possible that Davis has addressed and corrected the problem and haven't said anything (I truly don't think they'll ever admit a problem exists), or happenstance that 31's seem playing well more so with others?Don’t know...All I know is that the nearby station with the 31 is three years old. Sensor hasn’t been replaced.
No sir. 31's weren't factory installed until last year. That doesn't mean they weren't available at that point for the retro fit on older ISS's like mine.Not positive, but I think the 31 wasn't even available then. I installed my first one late 3/16 and I believe that was pretty much hot off the press.Do you guys think it's possible that Davis has addressed and corrected the problem and haven't said anything (I truly don't think they'll ever admit a problem exists), or happenstance that 31's seem playing well more so with others?Don’t know...All I know is that the nearby station with the 31 is three years old. Sensor hasn’t been replaced.
I believe I read on here somewhere that they started being shipped on some VP2's in December 2015. I could be wrong though.
I got a new ISS and 31 from Ryan a few weeks ago and I've been liking it so far. I had been using an old late 2006 ISS that came with an analog T/H when I bought it. After switching to digital sensors I had noticed I'd get strange spikes in RH a couple of times a day...i.e. I'd have an hour of something like 83-86% RH but I'd get 1 ob in there with 95% that would really stand out. That's gone now with the new transmitter.9VDC? Obviously, that's not a stock Davis FARS fan; what brand is it?
The past few days I've been hitting 99% RH at night and the dewpoint has seemed on par during the day. I'm running it with the filter off and the fan at 9V.
I'll have to find a link later. It's one of those 12V circular Xerox drum fans. I connect it to a variable AC adapter and run it at 9V because it doesn't like to startup at 12V even though it's rated for it. I got tired of forgetting it's off when the power comes back on after an outage. At 9V, no issues.I got a new ISS and 31 from Ryan a few weeks ago and I've been liking it so far. I had been using an old late 2006 ISS that came with an analog T/H when I bought it. After switching to digital sensors I had noticed I'd get strange spikes in RH a couple of times a day...i.e. I'd have an hour of something like 83-86% RH but I'd get 1 ob in there with 95% that would really stand out. That's gone now with the new transmitter.9VDC? Obviously, that's not a stock Davis FARS fan; what brand is it?
The past few days I've been hitting 99% RH at night and the dewpoint has seemed on par during the day. I'm running it with the filter off and the fan at 9V.
This maybe should be in a new thread, but I recently found the preliminary data sheet on the new SHT85 ...\:D/ However.... The Big But....Is the protocol compatible with our ISS's???
https://www.mouser.com/catalog/specsheets/Sensirion_10022018_HT_DS_SHT85_V0.9_D1.pdf
This maybe should be in a new thread, but I recently found the preliminary data sheet on the new SHT85 ...\:D/ However.... The Big But....Is the protocol compatible with our ISS's???
https://www.mouser.com/catalog/specsheets/Sensirion_10022018_HT_DS_SHT85_V0.9_D1.pdf
I liked that the SHT85 has a built-in heater! That is new I think.
Here is my take on this:
The SHT85 is pin for pin compatible with the SHT75 (electrically) and could be simply plugged in without any rewiring . Although the SHT85 appears to be I2C only, a simple firmware upgrade for the ISS would be required. As far as I know, this could only be done by Davis.
See:
https://www.mouser.com/catalog/additional/Sensirion_HT_AN_SHT85_Transitioning_SHT7x_to_SHT85_V0.9_D1.pdf
Has anyone compared that?For years and years. The fan is there to keep ambient air flowing across the sensor at all times, no matter what the wind is doing.
I am sorry I forgot to mention that if it affects the humidity part of the sensor.So it is said. To what degree I think has much to do with what climate the 31 is exposed to.
My thinking about all of this maybe we need to add dewpoint temperature when we talk about Relative Humidity being its only relative to the ambient temperature and not a good indicator of actual moisture content in the air which IMO is the issue.
100% at 32°F (0°c) for days is still very little moisture and won't oversaturate the sensor membrane is my thinking. Now take 85% at 65°+dp the sensor membrane is absorbing lots of moisture in just hours.
I have a Vantage Pro2 with 24 hr Aspiration Fan and was wondering if with a steady air movement across the SHT 31 sensor will keep it a little lower than the shield without a fan. Has anyone compared that?
I just did a dry/wet bulb test and it showed the humidity to be 87.9 and my console reading was 88% this is with the sht 75, looks real good, i tested several times with the same results. I found a good chart to calculate this with, it uses dry/wet/barometer inputs to calculate with.
Agree, but is Davis going to listen to us and begin working on the fix? If enough people complain or care enough to voice their concerns to Davis then maybe. The bottom line is if sales of the VP2 suffer then we have a better chance.I think that the VP2 owners here on this forum are a minuscule segment of their business and not worth a "drop everything that you're doing and fix it for these whiners" type of scenario. If it was a problem that was so obvious to ALL, then it might be a different story, but I think the vast majority are oblivious, or don't care enough to voice a complaint.
Agree, but is Davis going to listen to us and begin working on the fix? If enough people complain or care enough to voice their concerns to Davis then maybe. The bottom line is if sales of the VP2 suffer then we have a better chance.I think that the VP2 owners here on this forum are a minuscule segment of their business and not worth a "drop everything that you're doing and fix it for these whiners" type of scenario. If it was a problem that was so obvious to ALL, then it might be a different story, but I think the vast majority are oblivious, or don't care enough to voice a complaint.
I very well could be and hope I'm wrong, but doubtful because I'd think there'd be a fix already.
Granted, my SHT31 is "only" set for a minus 2% correction factor, considerably less than most, but you'll not see me throwing my VP2 out the window....not even a debate.What to do.Agree, but is Davis going to listen to us and begin working on the fix? If enough people complain or care enough to voice their concerns to Davis then maybe. The bottom line is if sales of the VP2 suffer then we have a better chance.I think that the VP2 owners here on this forum are a minuscule segment of their business and not worth a "drop everything that you're doing and fix it for these whiners" type of scenario. If it was a problem that was so obvious to ALL, then it might be a different story, but I think the vast majority are oblivious, or don't care enough to voice a complaint.
I very well could be and hope I'm wrong, but doubtful because I'd think there'd be a fix already.
I don't know about everyone else but I am getting impatient waiting for Davis to come up with a solution to the infamous wet bias of the 31.
My thoughts are:
I'm curious about a couple of things here:
1. What form would that "solution" have? Would it be hardware? Software? Or...
2. If a hardware solution, then would this be "send your ISS in for replacement"? Or optionally "do it yourself"?
3. What production lots of VP2s would be involved? That is, would it be available for all ages of VP2? Cabled in addition to wireless? Etc.
4. What would be the estimated cost?
5. How many units would you expect Davis to sell?
The problem cannot be adequately addressed through software because each sensor has varying amounts of bias, and those biases can change with time. I have 3 sensors. They all behave differently. No one solution would ensure each operates within specifications.Agree. It's not a meteorological sensor.
It's clearly a hardware problem. As has been pointed out many times already, Sensirion warns explicitly in the datasheet that the sensor isn't designed for environments with humidities above 80%. I mean how asinine is it that Davis (or anyone else) thought "screw it, we're doing it anyway?!" As Ron (kcidwx) said, this is an INDOOR sensor not intended for meteorology. He's an NWS field tech who's tested and verified the problem even with non-Davis branded SHT31s. Arguing that other manufacturers have implemented this sensor outdoors "successfully" is problematic because AFAIK, those claiming that haven't tracked non-Davis SHT31s long-term (particularly not with calibrated instrumentation). Just to make matters worse, Davis uses non-approved chemicals in mounting & packaging the sensor (material safety handling). So either way you slice it, Davis blew through vendor warnings about sensor corruption and the results are predictable.
Agree. It's not a meteorological sensor.
If someone has a separate temp/hum station, the probable way to go (if you're really bothered by the wet bias) is to measure the temp with your FARS/ISS and then use a passive shield with a 2nd SHTxx with some form of supplemental heat inside of the shield to keep the RH almost always < 80%. Then apply your own calculations to determine a new RH using the ISS 2m temp and the passive 2m dewpoint. I'm not sure if you could apply a resistor to the Davis temp/hum voltage line to create a little heat without affecting the sensor performance. That would be a question better answered by one of the electrical guys here.
Speaking more generally and to no one in particular, if you think accurate humidity isn't that important, you should go ask someone who runs a decent size farm whether correct evapo-transpiration calculations matter to them. Spoiler alert: a 5+% shift in humidity during peak growing season could mean wasting thousands of gallons of water ($$$) or, worse yet, under applying irrigation to thirsty crops. Keep in mind that agriculture is one of the primary targets for Davis products. So when the VP2 OVER reports humidity, irrigation is UNDER applied and this could cost farmers real money from lost yields (especially in hot and dry years).
Speaking more generally and to no one in particular, if you think accurate humidity isn't that important, you should go ask someone who runs a decent size farm whether correct evapo-transpiration calculations matter to them. Spoiler alert: a 5+% shift in humidity during peak growing season could mean wasting thousands of gallons of water ($$$) or, worse yet, under applying irrigation to thirsty crops. Keep in mind that agriculture is one of the primary targets for Davis products. So when the VP2 OVER reports humidity, irrigation is UNDER applied and this could cost farmers real money from lost yields (especially in hot and dry years).
Which is why I say someone needs to show up to some farm convention and find the Davis booth and start handing out informative flyers to everyone around the area. I bet Davis would then care very much and they will address the issue. If you can't get in the venue then hand out flyers at the entrance.
Speaking more generally and to no one in particular, if you think accurate humidity isn't that important, you should go ask someone who runs a decent size farm whether correct evapo-transpiration calculations matter to them. Spoiler alert: a 5+% shift in humidity during peak growing season could mean wasting thousands of gallons of water ($$$) or, worse yet, under applying irrigation to thirsty crops. Keep in mind that agriculture is one of the primary targets for Davis products. So when the VP2 OVER reports humidity, irrigation is UNDER applied and this could cost farmers real money from lost yields (especially in hot and dry years).
Which is why I say someone needs to show up to some farm convention and find the Davis booth and start handing out informative flyers to everyone around the area. I bet Davis would then care very much and they will address the issue. If you can't get in the venue then hand out flyers at the entrance.
I'm all for action over words (which is why I crafted my own custom solution to this problem after spending countless hours assessing and documenting it), but that sounds like a pretty good way to get sued by Davis. I suppose if you have the cash or if you are a consumer litigator, that might work. As with anything, there's always the likelihood that the truth is irrelevant to the proceedings -- in the courtroom or the court of public opinion. What's the saying? It's easier to fool people than to convince them they've been fooled?
The sensor shows best performance when operated within recommended normal temperature and humidity range of 5 – 60 °C and 20 – 80 %RH, respectively. Long term exposure to conditions outside normal range, especially at high humidity, may temporarily offset the RH signal (e.g. +3%RH after 60h at >80%RH). After returning into the normal temperature and humidity range the sensor will slowly come back to calibration state by itself. Prolonged exposure to extreme conditions may accelerate ageing.
We already know from previous discussion up thread that the Acurite indoor units can be expected to perform quite well for a time outdoors. But no one has exposed them long term. After all, they aren't shielded from the elements whatsoever so siting them properly year round would be ill advised.
Sensirion puts the following disclaimer in the datasheet for the sensor:QuoteThe sensor shows best performance when operated within recommended normal temperature and humidity range of 5 – 60 °C and 20 – 80 %RH, respectively. Long term exposure to conditions outside normal range, especially at high humidity, may temporarily offset the RH signal (e.g. +3%RH after 60h at >80%RH). After returning into the normal temperature and humidity range the sensor will slowly come back to calibration state by itself. Prolonged exposure to extreme conditions may accelerate ageing.
"Extreme conditions" here are defined as being below 5C (41F) or above 80% humidity regularly. Notice also how they use the term "normal". Under what scenario would an environment featuring temps above 41 and humidity between 20-80% be considered "normal"? The only one I can think of would be climate controlled (home, business, lab, greenhouse, humidor, etc).
I discovered something in the specs for the sht1x and sht7x series sensors that i had not read before or just overlooked. I was wondering why all my old sensors and the new 75's stopped at 99% and the Sensirion specs state (Values higher than 99%RH indicate fully saturated air and
must be processed and displayed as 100%RH1) this is why they don't go over 99% because Davis doesn't show the readings over 99% as 100% unless they are 99.5% or higher. The highest reading in dense fog on mine has been 99.4% with most at 99.1 to 99.2 percent. But according to specs they should be displayed as 100% by Davis are they should show the specs as 0 to 99% instead of 100%. So again it looks like Davis doesn't follow the Sensirion instructions. The 31's don't show that in the specs and both mine hit 100% in fog with one showing 99.9% and the other 99.7% so that looks like a change made with this sensor. ](*,)
Unless you are lucky and get one of the older sht's that gets to 99.5% you won't see a 100 ever.Thanks. As I stated here before, the 31 I have now (couple years old) refused to hit 100%, sat on 99 (zero correction factor), and that's after being WOXOF for hours, but all my comps were long since at 100%.
I have found that when i get a decent reading on one end the other is off on the other end.
The required change is to go with an I2C bus and get rid of LSS. Then they can use any current and future sensor. This is inevitable and Davis will need to do this at some point.
Here are the specs:
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Here are the specs:
[ You are not allowed to view attachments ]
It would be interesting if the temperature sensor performs well during the winter in your location Randy.
The required change is to go with an I2C bus and get rid of LSS. Then they can use any current and future sensor. This is inevitable and Davis will need to do this at some point.
Ahhh yes, but yet you proudly display owning three of them... :-PThe required change is to go with an I2C bus and get rid of LSS. Then they can use any current and future sensor. This is inevitable and Davis will need to do this at some point.
Inevitable like a color screen on its console, and wifi built-in?
Sorry, but I couldn’t resist poking fun at Davis, again, and its horribly dated technology.
Ahhh yes, but yet you proudly display owning three of them... :-PThe required change is to go with an I2C bus and get rid of LSS. Then they can use any current and future sensor. This is inevitable and Davis will need to do this at some point.
Inevitable like a color screen on its console, and wifi built-in?
Sorry, but I couldn’t resist poking fun at Davis, again, and its horribly dated technology.
The required change is to go with an I2C bus and get rid of LSS. Then they can use any current and future sensor. This is inevitable and Davis will need to do this at some point.
Inevitable like a color screen on its console, and wifi built-in?
Sorry, but I couldn’t resist poking fun at Davis, again, and its horribly dated technology.
Well, after 3 years of service, I retired my first 31 and slapped in another. So far so good, 16-ish hrs each day now are below 10% humidity and seems to be performing nicely. Will have to wait for the monsoon to see about the other end. I also finally replaced my original 12 year old C123, it was down to 2.3v. Certainly got my money's worth outta it. =D>
No doubt. The old one was dropping off the table below 5% or so. This one so far has not. I'll watch it like a hawk as usual, maybe Davis has figured out how to mount it properly. Maybe not....I'll keep y'all advised.Well, after 3 years of service, I retired my first 31 and slapped in another. So far so good, 16-ish hrs each day now are below 10% humidity and seems to be performing nicely. Will have to wait for the monsoon to see about the other end. I also finally replaced my original 12 year old C123, it was down to 2.3v. Certainly got my money's worth outta it. =D>
Nice! The Sensirion humidity sensors are better suited for your neck of the woods.
No doubt. The old one was dropping off the table below 5% or so. This one so far has not. I'll watch it like a hawk as usual, maybe Davis has figured out how to mount it properly. Maybe not....I'll keep y'all advised.Well, after 3 years of service, I retired my first 31 and slapped in another. So far so good, 16-ish hrs each day now are below 10% humidity and seems to be performing nicely. Will have to wait for the monsoon to see about the other end. I also finally replaced my original 12 year old C123, it was down to 2.3v. Certainly got my money's worth outta it. =D>
Nice! The Sensirion humidity sensors are better suited for your neck of the woods.
Well hell's bells, whaddaya want? That's exactly what we've been bitchin' about since Davis debuted the 31 three years ago. Granted, the 31 is "supposedly" only meant for indoor use, but Acurite uses a 31 for their little hand held device and works very well. IF, I repeat, IF Davis has solved this problem, then a lot of folks here go =D>. Frankly, I'm not holding my breath. We'll see.No doubt. The old one was dropping off the table below 5% or so. This one so far has not. I'll watch it like a hawk as usual, maybe Davis has figured out how to mount it properly. Maybe not....I'll keep y'all advised.Well, after 3 years of service, I retired my first 31 and slapped in another. So far so good, 16-ish hrs each day now are below 10% humidity and seems to be performing nicely. Will have to wait for the monsoon to see about the other end. I also finally replaced my original 12 year old C123, it was down to 2.3v. Certainly got my money's worth outta it. =D>
Nice! The Sensirion humidity sensors are better suited for your neck of the woods.
Not sure mounting will help much except to reduce wet bias.
Tell ya what, this new 31 has my attention. Granted, I've only been between 5 and 37% since installing it, but the dew has been rock solid, so much so I took out my -2% correction factor from the old 31 and now run it at flat 0. Obviously still early, but really like what I'm seeing, at least on the dry end.
I had Ryan send me two, so I just compared the old and the other new one. With that, to my eye, absolutely no mounting difference. On the sensor side they look exactly identical, revision number and all. Only noticeable difference is on the back side with the attached white sticker, it's completely different, could just be a stock number for all I know. So if it is different, Davis is keeping it under the cuff.Tell ya what, this new 31 has my attention. Granted, I've only been between 5 and 37% since installing it, but the dew has been rock solid, so much so I took out my -2% correction factor from the old 31 and now run it at flat 0. Obviously still early, but really like what I'm seeing, at least on the dry end.
Nice! Can you tell any difference the way Davis mounted the sensor?
I had Ryan send me two, so I just compared the old and the other new one. With that, to my eye, absolutely no mounting difference. On the sensor side they look exactly identical, revision number and all. Only noticeable difference is on the back side with the attached white sticker, it's completely different, could just be a stock number for all I know. So if it is different, Davis is keeping it under the cuff.Tell ya what, this new 31 has my attention. Granted, I've only been between 5 and 37% since installing it, but the dew has been rock solid, so much so I took out my -2% correction factor from the old 31 and now run it at flat 0. Obviously still early, but really like what I'm seeing, at least on the dry end.
Nice! Can you tell any difference the way Davis mounted the sensor?
I'm still tickled with it. Even though the monsoon is supposedly right around the corner, kinda wish one of you "wet" guys would give it another try. Not saying this sensor is a "new and improved version", but it's certainly performing better than my last one.I had Ryan send me two, so I just compared the old and the other new one. With that, to my eye, absolutely no mounting difference. On the sensor side they look exactly identical, revision number and all. Only noticeable difference is on the back side with the attached white sticker, it's completely different, could just be a stock number for all I know. So if it is different, Davis is keeping it under the cuff.Tell ya what, this new 31 has my attention. Granted, I've only been between 5 and 37% since installing it, but the dew has been rock solid, so much so I took out my -2% correction factor from the old 31 and now run it at flat 0. Obviously still early, but really like what I'm seeing, at least on the dry end.
Nice! Can you tell any difference the way Davis mounted the sensor?
Gotcha Let me know how it performs in the long run.
I'm still tickled with it. ...Not saying this sensor is a "new and improved version", but it's certainly performing better than my last one.
Who knows....
I'm still tickled with it. ...Not saying this sensor is a "new and improved version", but it's certainly performing better than my last one.
Who knows....
Could this be 8 times better than zero but that result is still zero?! I remember when the SHT31 was released, a few years ago, and we thought everything would be great. Unemployment in the US would disappear, the crime rate throughout the world would drop to near zero, inflation in Venezuela would disappear, and no further marriages would ever result in divorce! Ok, I may have gotten carried away but the point is it was a major disappointment—it was not the enhancement we were led to believe it was. Stupid me—I upgraded my two VP2s with the new sensor and ordered another VP2 with this godsend. Oh well...Damn Ron, whatta ya want? All I can do is tell you what I observe, and I like what I see. If it turns out to be another POS, oh well, but not so far.Quote
I've sent three back to him so far, the fourth is coming. His return policy is as good as it gets.I'm still tickled with it. ...Not saying this sensor is a "new and improved version", but it's certainly performing better than my last one.
Who knows....
Could this be 8 times better than zero but that result is still zero?! I remember when the SHT31 was released, a few years ago, and we thought everything would be great. Unemployment in the US would disappear, the crime rate throughout the world would drop to near zero, inflation in Venezuela would disappear, and no further marriages would ever result in divorce! Ok, I may have gotten carried away but the point is it was a major disappointment—it was not the enhancement we were led to believe it was. Stupid me—I upgraded my two VP2s with the new sensor and ordered another VP2 with this godsend. Oh well...Damn Ron, whatta ya want? All I can do is tell you what I observe, and I like what I see. If it turns out to be another POS, oh well, but not so far.Quote
I truly hope you are right, but as you stated, the newbie needs a good test in higher humidities before I send Ryan my credit card!
I'm still tickled with it. Even though the monsoon is supposedly right around the corner, kinda wish one of you "wet" guys would give it another try. Not saying this sensor is a "new and improved version", but it's certainly performing better than my last one.I had Ryan send me two, so I just compared the old and the other new one. With that, to my eye, absolutely no mounting difference. On the sensor side they look exactly identical, revision number and all. Only noticeable difference is on the back side with the attached white sticker, it's completely different, could just be a stock number for all I know. So if it is different, Davis is keeping it under the cuff.Tell ya what, this new 31 has my attention. Granted, I've only been between 5 and 37% since installing it, but the dew has been rock solid, so much so I took out my -2% correction factor from the old 31 and now run it at flat 0. Obviously still early, but really like what I'm seeing, at least on the dry end.
Nice! Can you tell any difference the way Davis mounted the sensor?
Gotcha Let me know how it performs in the long run.
Who knows....
Had a little MCS south of the border finally push some BL moisture our way, dew's been in the 50's to low 60's and this new 31 is still rockin' it. There is zero doubt in my mind this is an improvement over my last one. Now, whether that's coincidence or by design, I have no idea, but it works. If I'm lucky, I may see some actual rain today and will continue to hawk it, cause we're gonna dry right the bleep out again after today as the non-soon continues.
I managed a whopping 0.04" of rain on Sunday with the dew in the mid-upper 60's for a while, briefly touched 71, still looking good. Need to see some much better/longer saturation though, I imagine that's what most are waiting to see me report, myself included...Had a little MCS south of the border finally push some BL moisture our way, dew's been in the 50's to low 60's and this new 31 is still rockin' it. There is zero doubt in my mind this is an improvement over my last one. Now, whether that's coincidence or by design, I have no idea, but it works. If I'm lucky, I may see some actual rain today and will continue to hawk it, cause we're gonna dry right the bleep out again after today as the non-soon continues.
Nice!
I guess I need to order a new SHT31 (already replaced it once because of unacceptable results) for my VP2 with the 24 hour fan. See attached screenshot from CWOP showing the data from my 3 Davis VP2s. The newest one and the unit that has the 24 hour fan is FW3075. My older units, which have the daytime fan together with the SHT31, are stations CW5020 and FW4350. The ISSs are located within 25 feet or so of each other, same height on the same fence. I verified that the fans in all three VP2s are working—receiving a lot of sun today! Humidity looks reasonable on station FW3075 but not the temperature and three nearby airports confirm these results. How disappointing to say the least.
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Yes. The only time knowing the humidity that's worth a damn is 100%.I guess I need to order a new SHT31 (already replaced it once because of unacceptable results) for my VP2 with the 24 hour fan. See attached screenshot from CWOP showing the data from my 3 Davis VP2s. The newest one and the unit that has the 24 hour fan is FW3075. My older units, which have the daytime fan together with the SHT31, are stations CW5020 and FW4350. The ISSs are located within 25 feet or so of each other, same height on the same fence. I verified that the fans in all three VP2s are working—receiving a lot of sun today! Humidity looks reasonable on station FW3075 but not the temperature and three nearby airports confirm these results. How disappointing to say the least.What are the dewpoints running on the 3 stations?
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Humidity looks good so the hot sensor issue I lean toward shield location or fan issue.Hey Ron, don't laugh, but I recall not too long ago that some stock fans were running backwards. Sure yours is sucking from the bottom and not blowing?
Humidity looks good so the hot sensor issue I lean toward shield location or fan issue.Hey Ron, don't laugh, but I recall not too long ago that some stock fans were running backwards. Sure yours is sucking from the bottom and not blowing?
Does anyone have experience from HYT 221? The only piece of information from Arduino forum claims that it's better than SHTs. I am considering buying one or two of HYTs for further tests.
You can't use the HYT 221 because it is I2C protocol. The Davis ISS is not compatible with I2C sensors. The Davis ISS uses LSS (Legacy Sensirion Sensibus) protocol. Which is why you can't use the SHT35/SHT85 since they only come with I2C protocol support. There are different versions of previous SHTxx to respectively support either LSS or I2C. Meaning you can't use just any SHT31 for example.I didn't express this in my previous post, but I use Arduino and use it with sensors directly, since I don't have a Davis. This thread is just the only one in the internet, which deals with SHT31 aging and bias problems. I hope my observations are helpful. I will tell how HYT 221 works, if I happen to buy a couple of them.
Interesting that you find that the SHT31 has a dry bias, as some others have reported a wet bias.
You can't use the HYT 221 because it is I2C protocol. The Davis ISS is not compatible with I2C sensors. The Davis ISS uses LSS (Legacy Sensirion Sensibus) protocol. Which is why you can't use the SHT35/SHT85 since they only come with I2C protocol support. There are different versions of previous SHTxx to respectively support either LSS or I2C. Meaning you can't use just any SHT31 for example.I didn't express this in my previous post, but I use Arduino and use it with sensors directly, since I don't have a Davis. This thread is just the only one in the internet, which deals with SHT31 aging and bias problems. I hope my observations are helpful. I will tell how HYT 221 works, if I happen to buy a couple of them.
Interesting that you find that the SHT31 has a dry bias, as some others have reported a wet bias.
You can't use the HYT 221 because it is I2C protocol. The Davis ISS is not compatible with I2C sensors. The Davis ISS uses LSS (Legacy Sensirion Sensibus) protocol. Which is why you can't use the SHT35/SHT85 since they only come with I2C protocol support. There are different versions of previous SHTxx to respectively support either LSS or I2C. Meaning you can't use just any SHT31 for example.I didn't express this in my previous post, but I use Arduino and use it with sensors directly, since I don't have a Davis. This thread is just the only one in the internet, which deals with SHT31 aging and bias problems. I hope my observations are helpful. I will tell how HYT 221 works, if I happen to buy a couple of them.
Interesting that you find that the SHT31 has a dry bias, as some others have reported a wet bias.
Please get them and let us know. It’s a sensor that I recommended Davis to consider switching too. Would love to see how the HYT would match up with a nearby ASOS or a Psychro-Dyne
Nice easterly wave moving through late tonight and well into tomorrow with lots of PWAT, so heavy rainers are likely. This should finally be a good saturation test (I hope) for this new 31. My impression to this point hasn't changed, it's doing a very nice job and what saturation I have had (up to 93% and mid 70's dew), it has recovered just fine.
Please get them and let us know. It’s a sensor that I recommended Davis to consider switching too. Would love to see how the HYT would match up with a nearby ASOS or a Psychro-Dyne
Please get them and let us know. It’s a sensor that I recommended Davis to consider switching too. Would love to see how the HYT would match up with a nearby ASOS or a Psychro-Dyne
I bought a couple HYT 221s and now one of them has been outside for over 2 weeks.
The first observation is related to their mountings. SHT21 is inside a proper humidity probe, so it has good ventilation. HYT 221 is inside a punctured Kinder Surprise Egg. Also, I don't have a FARS, so HYT 221's humidity level may lag behind the truth at calm evenings. At days, the lag doesn't seem to be so large, because the days are rarely calm here.
The second thing is that HYT 221 measures nearly always lower humidity levels than the old SHT21. This is kinda expected, since almost all Sensirion sensors tend to have a small wet bias (but my SHT31 had bad dry bias). Their temperatures are within 0.1-0.3 degrees of Celsius, so both have good precision at temperature measurement.
For the third, dew point of HYT 221 seems to be more correlated with a nearby meteorological institute station (less than 1km away) than SHT21 is. Dewpoint correlation between HYT and the official station is 0.9802, whereas dewpoint correlation SHT and official is 0.9716.
At windy days, dew points of HYT221 are very close to the official station. At wet days, HYT 221 doesn't climb so easily to 99 % as SHT21 does (HYT 221 has climbed up to 99.4% so far, if anyone wonders). I don't think that HYT 221's poor casing can explain the slow climb speed fully, but I can be wrong. Maybe I should remove the Egg completely, because HYT221 has a protective grid against droplets by itself.
Both HYT221 and SHT21 report too high humidities after rain, but that's because my decrepit radiation shield absorbs water and is located near to bushes and grass.
I also think that the "official" station has a slight wet bias at 90%+ humidity levels, because it looks to report 100% even if there are no fog at all, but who knows.
Edit: I still underline, that the distributions of TD differences maybe lie a little bit: there have been many wet days recently, and then TD is almost the same as T. SHT looks to the have edge over HYT at those times, but not during dry weather. For instance: the weather is cloudy, cool and dryish now, and the difference HYT TD - official TD is +0.2 C while SHT TD - official TD is +1.3 C. In conclusion, I have to examine high level humidity measurement capabilities of HYT 221 more and of course its aging over time. SHT31 was also superb accurate at first, but became complete trash within months or so.
Please get them and let us know. It’s a sensor that I recommended Davis to consider switching too. Would love to see how the HYT would match up with a nearby ASOS or a Psychro-Dyne
I bought a couple HYT 221s and now one of them has been outside for over 2 weeks.
The first observation is related to their mountings. SHT21 is inside a proper humidity probe, so it has good ventilation. HYT 221 is inside a punctured Kinder Surprise Egg. Also, I don't have a FARS, so HYT 221's humidity level may lag behind the truth at calm evenings. At days, the lag doesn't seem to be so large, because the days are rarely calm here.
The second thing is that HYT 221 measures nearly always lower humidity levels than the old SHT21. This is kinda expected, since almost all Sensirion sensors tend to have a small wet bias (but my SHT31 had bad dry bias). Their temperatures are within 0.1-0.3 degrees of Celsius, so both have good precision at temperature measurement.
For the third, dew point of HYT 221 seems to be more correlated with a nearby meteorological institute station (less than 1km away) than SHT21 is. Dewpoint correlation between HYT and the official station is 0.9802, whereas dewpoint correlation SHT and official is 0.9716.
At windy days, dew points of HYT221 are very close to the official station. At wet days, HYT 221 doesn't climb so easily to 99 % as SHT21 does (HYT 221 has climbed up to 99.4% so far, if anyone wonders). I don't think that HYT 221's poor casing can explain the slow climb speed fully, but I can be wrong. Maybe I should remove the Egg completely, because HYT221 has a protective grid against droplets by itself.
Both HYT221 and SHT21 report too high humidities after rain, but that's because my decrepit radiation shield absorbs water and is located near to bushes and grass.
I also think that the "official" station has a slight wet bias at 90%+ humidity levels, because it looks to report 100% even if there are no fog at all, but who knows.
Edit: I still underline, that the distributions of TD differences maybe lie a little bit: there have been many wet days recently, and then TD is almost the same as T. SHT looks to the have edge over HYT at those times, but not during dry weather. For instance: the weather is cloudy, cool and dryish now, and the difference HYT TD - official TD is +0.2 C while SHT TD - official TD is +1.3 C. In conclusion, I have to examine high level humidity measurement capabilities of HYT 221 more and of course its aging over time. SHT31 was also superb accurate at first, but became complete trash within months or so.
Old Japanese proverb: "No FIXEE what ain't BROKEE."Well, that's just it, everybody and their brother says it sucks...and there's been tons of data that backs that conclusion. All I've been saying is that perhaps the issue has been dealt with.
Old Japanese proverb: "No FIXEE what ain't BROKEE."Well, that's just it, everybody and their brother says it sucks...and there's been tons of data that backs that conclusion. All I've been saying is that perhaps the issue has been dealt with.
And frankly tired of saying this over and over, you'll never know til you try.Old Japanese proverb: "No FIXEE what ain't BROKEE."Well, that's just it, everybody and their brother says it sucks...and there's been tons of data that backs that conclusion. All I've been saying is that perhaps the issue has been dealt with.
Possibly dealt with but based on prior experience unlikely.
And frankly tired of saying this over and over, you'll never know til you try.Old Japanese proverb: "No FIXEE what ain't BROKEE."Well, that's just it, everybody and their brother says it sucks...and there's been tons of data that backs that conclusion. All I've been saying is that perhaps the issue has been dealt with.
Possibly dealt with but based on prior experience unlikely.
Damn people, it's not like I'm asking y'all to buy a $1000 piece of equipment that you can't return, it's $40....and you can return it. I'm sick and tired of being the only who's TRYING here. If it still sucks, oh well, send the GD thing back. Mine works fine. :roll:
Fine. Ryan has stated to me all his returns go back to Davis, that's his business. You'd think after countless returns to Davis, they'd start to get the picture....that's the whole point of returns here.And frankly tired of saying this over and over, you'll never know til you try.Old Japanese proverb: "No FIXEE what ain't BROKEE."Well, that's just it, everybody and their brother says it sucks...and there's been tons of data that backs that conclusion. All I've been saying is that perhaps the issue has been dealt with.
Possibly dealt with but based on prior experience unlikely.
Damn people, it's not like I'm asking y'all to buy a $1000 piece of equipment that you can't return, it's $40....and you can return it. I'm sick and tired of being the only who's TRYING here. If it still sucks, oh well, send the GD thing back. Mine works fine. :roll:
I have tried three times and failed. I really don’t like returning items too. Adds too much complexity to a small business like Ryan and other honest business people run.
dewpoints trouble point 60's +No trouble for me...as in none...zip, zero, zilch.
BTW: How exactly close are the Dew Points between the HYT sensors and the official observations?
Ok so i just ordered another 31 for testing from Ryan at S.I. now that we are getting into the high humidity season down here on the coast near the Gulf of Mexico. I sometimes get humidity readings above 95% for days at a time during the winter months. I think i am wasting my money but just have to try one more time to see if i can get a good long run of good readings. My accurite meter has been outside a lot over the last year and is still working just fine so i know the 31 can work real well over a long period of time. Will get it set up and running for the winter and will give updates as needed.
Granted, I don't live in the most humid of places, but I've spent the last two months with dew points consistently in the 60's. The monsoon doesn't always bring rain, but it always brings humidity and the 31 did fine. Just sayin'.......... :roll:Ok so i just ordered another 31 for testing from Ryan at S.I. now that we are getting into the high humidity season down here on the coast near the Gulf of Mexico. I sometimes get humidity readings above 95% for days at a time during the winter months. I think i am wasting my money but just have to try one more time to see if i can get a good long run of good readings. My accurite meter has been outside a lot over the last year and is still working just fine so i know the 31 can work real well over a long period of time. Will get it set up and running for the winter and will give updates as needed.Nice Jerry, now we will know for sure =D>
BTW: How exactly close are the Dew Points between the HYT sensors and the official observations?
I'm still running the comparisons. So far HYT221 seems to rise slower to higher humidity levels than the official one. It has also maxed out to 99.99% at super humid day. Dew points are very close to each other, if it's windy and humidity is less than 90.
And for everybody who are interested, here's another guy's realtime comparison of Vaisala and SHT31: https://www.mrsoft.fi/current.htm
I bet his Vaisala sensors are of type HMP60 or HMP110 (the cheapest ones you can buy from Vaisala). If I had spare money, I would buy also one of those and compare SHT31, HYT221 and HMP60 in the exactly same conditions.
I agree with this assessment, no fan. Sitting has nothing to do with responsiveness, only accuracy.Please get them and let us know. It’s a sensor that I recommended Davis to consider switching too. Would love to see how the HYT would match up with a nearby ASOS or a Psychro-DyneI don't have a FARS, so HYT 221's humidity level may lag behind the truth at calm evenings. At days, the lag doesn't seem to be so large, because the days are rarely calm here.
wrapped it in a damp washcloth for a couple of hours to get it moistened up.Not saying it's wrong or right, but I didn't do that. The only thing I did different was use the SF2 cap from the get-go.
wrapped it in a damp washcloth for a couple of hours to get it moistened up.Not saying it's wrong or right, but I didn't do that. The only thing I did different was use the SF2 cap from the get-go.
It is working just fine right now and now have to see if it keeps on going.Maybe.....just maybe....I was right. Let alone the obvious that I want this sensor to perform to humidity spec, I want some vindication as well because not a damn soul here has believed a word I've said. ](*,)
Update, i just moved the 31 to my website so i can monitor it from anywhere. It is working just fine right now and now have to see if it keeps on going.
It is working just fine right now and now have to see if it keeps on going.Maybe.....just maybe....I was right. Let alone the obvious that I want this sensor to perform to humidity spec, I want some vindication as well because not a damn soul here has believed a word I've said. ](*,)
All I have been wanting for several months is someone to step up and see if my findings are unique or that an actual "change" to the sensor was successfully accomplished. Obviously my word alone isn't good enough....and I get that, just gets tiring spouting my findings that are being dismissed because it's "just me" with no corroboration. Whether Jerry or anyone else agrees or doesn't agree with my findings, so be it, at least we know someone else gave it a shot. Regardless, mine's a keeper, and hopefully others will find this as well.It is working just fine right now and now have to see if it keeps on going.Maybe.....just maybe....I was right. Let alone the obvious that I want this sensor to perform to humidity spec, I want some vindication as well because not a damn soul here has believed a word I've said. ](*,)
Definitely not a belief or a trust thing, it’s just that I’ve had a different result from the side by side comparisons I’ve done. But I will say this is definitely one of those circumstances where I look forward to be proven wrong. Here’s hoping Jerry sees something different ...
I am really waiting for the time of year when the fog and coastal trofs get going and the humidity stays on the high end for days at a time, that will be the real test.No doubt. Mine spent almost all of the last two months with dew points in the 60's and the occasional 70's, but nothing like the "days on end" of wetness you guys get.
I know it works fine out of the package and now only time will tell.I forgot to ask, did you use the SF2 cap on this new one? Like I said earlier, I put the cap on out-of-the-box for the first time with this 31. I think it may actually help with keeping the "saturation" from the sensor itself. I have no proof of this, only an "educated" speculation. If I had my druthers, I'd like to see two 31 compared together without a cap for a base line, then one with and the other remaining without to see if there's a difference worth noting.
I have ordered a bunch of SF2 caps and since I have 3 Davis VP2s with the world-class SHT sensor, I will try the SF2 caps on two of my stations and not the other and see what kind of results I get.Thank you. Not that you still can't compare, but all your 31's are "older", are they not? What I'm getting at is perhaps this "protection" is necessary from the get-go so the sensor isn't permanently "spoiled".
I am glad to see it working so well these first couple of days and got my fingers crossed for the long haul.Once again, not your climate, but my current 31 went into service exactly four months ago today.
I have ordered a bunch of SF2 caps and since I have 3 Davis VP2s with the world-class SHT sensor, I will try the SF2 caps on two of my stations and not the other and see what kind of results I get.Thank you. Not that you still can't compare, but all your 31's are "older", are they not? What I'm getting at is perhaps this "protection" is necessary from the get-go so the sensor isn't permanently "spoiled".
BTW, PM will be forth coming.
I have no idea. All I know is I bought this latest one in June.my latest one is probably 18 months old. Is that too old?I have ordered a bunch of SF2 caps and since I have 3 Davis VP2s with the world-class SHT sensor, I will try the SF2 caps on two of my stations and not the other and see what kind of results I get.Thank you. Not that you still can't compare, but all your 31's are "older", are they not? What I'm getting at is perhaps this "protection" is necessary from the get-go so the sensor isn't permanently "spoiled".
BTW, PM will be forth coming.
So the Davis 31 is in the +6% to +7% from true as best I can tell in this humidity range.
Well i finally got a run on high humidity, the humidity stayed between 95% and 100% for nearly two days and the new 31 worked just fine when the humidity dropped today down to 35%. There was no sign of wet bias but this is just the first time with high humidity and things could change as i get more of the really wet days so will keep updating when conditions warrant.Well I know the new one I have will hit 1% cause I did it several times yesterday with an accompanying negative mid 30's dew point, which I thought was ridiculous til I saw two RAWS sites in the negative 50's. The air mass is just a tiny bit dry...
Well i finally got a run on high humidity, the humidity stayed between 95% and 100% for nearly two days and the new 31 worked just fine when the humidity dropped today down to 35%. There was no sign of wet bias but this is just the first time with high humidity and things could change as i get more of the Rreally wet days so will keep updating when conditions warrant.
The new sensor topped out at 99%, doing just fine on top and bottom and this reading was without heavy fog just like fog and drizzle.
Update time new 31 is working real well, no signs of wet bias.If I asked this before, I apologize, but are you using the SF2 cap one your new 31? My new 31 has had it on from day one, don't know whether it helps for sure (I actually believe it does in wetter conditions), but it certainly doesn't hurt.
Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:Thanks. No doubt SF2 provides better protection than the stock filter does, but as far as the silk...? I think the SF2 keeps the sensor itself from becoming saturated as it would unprotected or with the stock filter. I truly believe it helps with recovery.
Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:Thanks. No doubt SF2 provides better protection than the stock filter does, but as far as the silk...? I think the SF2 keeps the sensor itself from becoming saturated as it would unprotected or with the stock filter. I truly believe it helps with recovery.
Not sure I'd call the SF2 a band aid, it's a Sensirion made option. Regardless, if it makes my PWS better without breaking the bank, I'm all for it. Suppose that's why I graduated from an SHT11 to a 15 to a 31, put in a case fan, use a Rainwise 111 as my hard wired tipper, and have my anny separate from my ISS. All good. =D>Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:Thanks. No doubt SF2 provides better protection than the stock filter does, but as far as the silk...? I think the SF2 keeps the sensor itself from becoming saturated as it would unprotected or with the stock filter. I truly believe it helps with recovery.
Isn’t goofy that we have to put “band-aids” on Davis products to make them work correctly? Oh well, there isn’t much (any?) competition in their product price range so I guess we have keep developing and using our band aids.
Jerryg, have you seen a manufacture date on your sensor?I know the question was not directed at me, but I know of no way of to determine the manufacture date other than go to Davis or Sensirion (I guess). There is labeling, but not with an apparent date.
C2274, you’ve probably mentioned this before, but what do you use to mount the SF2?
The newest Davis 31 I have has a sticker on the back with the part number and ”190610 DS” on it. I just assumed that’s either a manufacture or inspection date and initials. Total assumption obviously, but seemed reasonable.My old 31 from 3+ years ago has I60216SB. There is a "16" in it....
Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:
I think testing would have to be somewhat long term, not just a few days, but IMO a properly sealed SF2 cap is without a doubt the way to best protect the sensor. That's exactly what it's designed to do.Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:
I’m curious to what your results are.
What i was looking at is if there is any difference in response time between the types of filters. The silk has the best time of the three with the sf2 being next and the Davis last which my be due to the large size of the filter rather than the material. The factory filters fit down tight on the sensor so have very little air space to moisten up and better response. Now the silk filter will not let water pass just vapor and where i live out in the country the only thing i really need to worry about is dust which is pretty heavy when the farmers are plowing for planting and harvesting the crops. No real gas vapors to worry about. We had very dense fog this am and the 31 did not show any bias once again, so looking good still.
:grin: well i have had a bunch of upper 90's on the humidity side and the sensor has worked just fine so far no sign of any bias at all. I am still waiting for one of the long drawn out periods where the humidity is in the high 90's for several days.Well to be sure I'll never see that, just looking for some true saturation for several hours. Thanks for checking in and bringing more hopeful news!
Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:Thanks. No doubt SF2 provides better protection than the stock filter does, but as far as the silk...? I think the SF2 keeps the sensor itself from becoming saturated as it would unprotected or with the stock filter. I truly believe it helps with recovery.
What case fan are you using and is it solar powered?
Thanks,
tweatherman
No solar. It's 120vac from the house then has a transformer included that converts it to 12vdc for the fan. The size is 80x80x25mm and there's a ton of choices. I suggest no less than 20CFM.Yes and no, i had the sf2 on the old and new for a few days and then put Davis filter on the new one to see if i could see any difference but could not detect any. Now today i just replaced both filters with the silk to test further. I am trying out several things right now out of curiosity if nothing else :grin:Thanks. No doubt SF2 provides better protection than the stock filter does, but as far as the silk...? I think the SF2 keeps the sensor itself from becoming saturated as it would unprotected or with the stock filter. I truly believe it helps with recovery.
What case fan are you using and is it solar powered?
Thanks,
tweatherman
I just read the whole thread to understand this whole SHT 31 situation.Mine's fine too... :roll:
Seems like Jerry has had better luck with this newest sensor.
How is it going for others out there with recent new SHT 31 sensors.
I'm not an engineer, but I would think from the reading that there are a limited number of ways for a humidity sensor, of the types that electronic stations use and excluding blonde hair or horse hair gizmos of the 40s, can work.
That being said, why would a sensor be substantially different from others, if the design were nearly the same. Why would one be more sensitive to high humidity damage than others?
I know that Young and Vaisala have some very long life, extreme conditions, types of humidity sensors. Are their construction that much more expensive than the glut of low cost things that are like the SHT stuff or the little almost pennies, ones for Arduino etc?
Anyone know the science behind it?
...As johnd has pointed out numerous times, aside from a few of us who are frustrated by the humidity performance, most users are probably either oblivious or indifferent to the humidity performance, so if it hasn't been improved in 14 years, I can't imagine many resources are being put into improving accuracy.
Its interesting to hear the platinum wire sensor wasn't as accurate in those settings (I know we're talking humidity here) but a R M Young device has a platinum wire sensor and is very expensive so one would think that if there weren't accuracy behind it, even the US Government and Universities with deeper pockets would opt for the method that gives best results.
I may be completely in left field, but my 31 is about 6 months old and I still think using the SF2 cap from the get go (which I did, never have before) may aid in not letting the sensor get too "wet" and delaying proper drying. Regardless, I'm still happy with it....that's my story and I'm sticking to it.
The sensor certainly does have a finite service life, but most of our users typically get 5-10 years from their sensors before significant issues are reported.
Where can one buy the SF2 cap?https://www.mouser.com/ProductDetail/Sensirion/SF2?qs=wWC4CIiyLaNCAejbFUK5dw%3D%3D
Thanks. Guess this is a must where I am located with damp foggy snow melt days etc.Whether the cap is a "must" for you or anyone else, I honestly can't say, it merely seemed like a logical step to try when I installed my latest 31.
Did you notice if this slowed down temperature or humidity response?
I am planning on 24 hour FARS so i guess more reason CAP is a must
One more question, did you have to remove the board from the radiation shield to install, or just take apart radiation shield?
Thanks
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Thanks.The stock cap merely snaps out. The holes are inside the cap next to the sensor, you'll see. As far as rust, never crossed my mind, however I live in one of the most dry climates on the planet. Just check it occasionally after install.
So if I understand correctly the stock filter (circled blue) in below image must be removed and the SF2 CAP placed stuck into the black tar like stuff and wire run between the 2 holes circled red in image below?
Any tips on removing? Prying this off brand new board will be nerve wracking.
Guess some thin insulated eletric wire to avoid rust or something is what you used?
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Upon reflection, I'm pretty sure the holes the stock filter snaps into are the holes I used for the wire. Merely trying to avoid confusion.Thanks.The stock cap merely snaps out. The holes are inside the cap next to the sensor, you'll see.
So if I understand correctly the stock filter (circled blue) in below image must be removed and the SF2 CAP placed stuck into the black tar like stuff and wire run between the 2 holes circled red in image below?
Any tips on removing? Prying this off brand new board will be nerve wracking.
Guess some thin insulated eletric wire to avoid rust or something is what you used?
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I'm not an engineer, but I would think from the reading that there are a limited number of ways for a humidity sensor, of the types that electronic stations use and excluding blonde hair or horse hair gizmos of the 40s, can work.
That being said, why would a sensor be substantially different from others, if the design were nearly the same. Why would one be more sensitive to high humidity damage than others?
I know that Young and Vaisala have some very long life, extreme conditions, types of humidity sensors. Are their construction that much more expensive than the glut of low cost things that are like the SHT stuff or the little almost pennies, ones for Arduino etc?
Anyone know the science behind it?
Thank you for your inquiry.
There are many things that can influence the accuracy and lifetime of the sensor, especially in outdoor applications.
We used to have a definition of normal operating range with the SHT2x:
Working outside of the normal range you may have to consider additional effects.
One important document is our handling instructions.
http://www.sensirion.com/file/handling_instructions_rht
This document is listing some points to consider, but they're not too relevant for outdoor conditions. The VOC levels are usually very low.
The biggest challenge outdoor are the dew cycles that can lead to corrosion. The electronics need to be protected with conformal coating and the manufacturers have to protect the sensor during that process.
Additionally some regions can be more harmful to the sensor. Airports, heavy traffic areas or proximity to the coast is also known to have adverse effects on sensor lifetime.
I haven't heard many reports about those failures. Do you have more in-depth knowledge if those products applied conformal coating or not?
Are there weather stations equipped with Vaisala sensors that last longer?
What? "Normal" range only goes up to 90% RH? Apparently SENSIRION avoids FOG!
The biggest challenge outdoor are the dew cycles that can lead to corrosion. The electronics need to be protected with conformal coating and the manufacturers have to protect the sensor during that process.
I haven't heard many reports about those failures. Do you have more in-depth knowledge if those products applied conformal coating or not?
Are there weather stations equipped with Vaisala sensors that last longer?
Does anyone know what Vaisala uses for temp/hum sensors so that I can respond back to Sensirion?
How about knowledge about what type of conformal coating chemistry Davis uses? (Acrylic, Epoxy, Polyurethane, Silicone, Fluorinated or non Fluorinated - Poly-Para-Xylylene (Parylene), or Amorphous Fluoropolymer)
Seeing 90% is normal range cap, have to rethink things... unreal they would go with 90% as normal cap sensor.I don't even know what that means. Every properly working 31 will easily get RH's in the upper 90's, my last would reached 99% all the time, it was the below 5% range that caused me to replace it with this current 31. :roll:
:shock:or is it #-o
Is the above normal range chart for the SHT31?
Wow if yes. or perhaps the Davis custom sensor was wider range, I dont know anymore guys...
I do have some additional comments.
The normal range doesn't tell you it's not possible to operate the sensor outside that range. There are just side effects that have to be considered. For instance at high RH levels the RH reading may drift and that's a reversible effect. It's just getting more complicated when operated outside of normal range.
I've heard of people wanting to replace the sensor of Davis stations. And as you state correctly that's not possible because the LSS version isn't available.
I don't know about Davis strategy and why they don't change to the DIS [I2C] version. It might involve a lot of extra work and compatibility issues making it hard to support previous versions after changing the design.
From what I've experienced so far this doesn't seem to be a huge issue with people wanting to replace the sensor themselves. I've only received a few requests so far and haven't been concerned. But I understand that for those affected by a non-working sensor it would be much easier to replace it themselves.
Looking at the Vaisala picture I think it only shows the sensing element. It seems to be porous material and most likely based on capacitive technology as well.
Given the fact that the sensing element is much bigger than the thin material layer on a CMOS chip, an eventual degradation process would take longer to affect the readings.
As it's still capacitive technology it would still be affected by molecules of a similar size as water such as VOCs.
If you receive feedback from Davis I'd be happy to hear about it. But I doubt they'll provide detailed information about their strategy and eventual change to the I2C interface.
I responded to Sensirion and told them that I had reached out to Davis inquiring about their conformal coating strategy. I have not heard back from Davis regarding this yet, but if I do I will share it and also forward it on to my new contact at Sensirion.
I considered using approved glue but frankly decided it was too difficult to do properly without making a sensor destroying mess (damn thing is soooo small), hence my decision to use wire to seal it down.I responded to Sensirion and told them that I had reached out to Davis inquiring about their conformal coating strategy. I have not heard back from Davis regarding this yet, but if I do I will share it and also forward it on to my new contact at Sensirion.For those with the SF2 or considering it, they also recommend adhesives that can be safely used including Loctite 401
How is humidity variance past few days after sensor went above normal range limit of 90%?I'll assume your question is for me. There is no drift, the sensor is just as "in-line" before as it was after.
did 5% drift effect start?
Not the "Sensirion jump" to 100% for one update cycle.Hadn't heard that one before, but it's spot on. My last 31 would indeed hit 100%, but if you blinked, you missed it. This current one won't even do that, but it's still a better overall performer.
So I decided to do a little holiday baking ... with my temp/hum sensors. My hope was to remove the wet bias in drier conditions but also found surprisingly better performance at saturation after the bake.
I have a new Davis SHT31 (which I believe was manufactured in June 2019) that I've reported on in this forum with disappointing results. I also have a few SHT75s. I baked them all per Sensirion's datasheet for 10hrs at 220°F. I did not bother with the rehydration procedure because it's the Puget Sound in December ... they will get plenty of hydration.
The SHT75 I used for the test had been outside for about 9mos. When I brought it in it read about 4% high at room temperature compared to my Belfort pyschrometer @ 40% RH. The new Davis SHT31 has been inside aside from a week of testing outside a few weeks ago. It was 6% high and +3°F dew point compared to the Belfort even having been acclimated to the dry conditions of a heated house.
After baking I tested them against a Belfort psychrometer at room temperature. Temperature results were so accurate at 72°F among all sensors that there is nothing to note.
The Belfort results were:
72.3°F Dry Bulb/59.0°F Wet Bulb giving: Humidity 45% Dew Point 50°F
Davis SHT31:
72.3°F 43% DP: 49°F
SHT75:
72.3°F 42% DP: 48°F
Not necessarily surprising after 10hrs at 220°F. I then put the sensors outside in what has been near saturation conditions. I expected the sensors to carry a dry bias at high humidity. Surprisingly, I found the opposite.
Before the bake, I could not get the SHT31 above 98%. Now it goes to 100% and actually stays there. Not the "Sensirion jump" to 100% for one update cycle. The SHT75 before the bake would get to 98% and stay there with a jump periodically to 99 or 100%. Now it goes to 99% and stays there. It will jump to 100% but not sustain it like the 31.
Obviously the real test will be as conditions dry out. Unfortunately, that happens infrequently here this time of year. We've only gotten as low as the 80%s and there are signs of the SHT75 drying out better, but only by a percent or two and when you consider it being 1% low at 100%, I would say that's negligible.
Just thought I'd pass along as I was surprised by the high humidity results. I have a feeling that if it does dry out, I will be right back to where I was before the bake with all this high humidity, but if we get a dry day, I'll post the results.
So I decided to do a little holiday baking ... with my temp/hum sensors. My hope was to remove the wet bias in drier conditions but also found surprisingly better performance at saturation after the bake.
I have a new Davis SHT31 (which I believe was manufactured in June 2019) that I've reported on in this forum with disappointing results. I also have a few SHT75s. I baked them all per Sensirion's datasheet for 10hrs at 220°F. I did not bother with the rehydration procedure because it's the Puget Sound in December ... they will get plenty of hydration.
The SHT75 I used for the test had been outside for about 9mos. When I brought it in it read about 4% high at room temperature compared to my Belfort pyschrometer @ 40% RH. The new Davis SHT31 has been inside aside from a week of testing outside a few weeks ago. It was 6% high and +3°F dew point compared to the Belfort even having been acclimated to the dry conditions of a heated house.
After baking I tested them against a Belfort psychrometer at room temperature. Temperature results were so accurate at 72°F among all sensors that there is nothing to note.
The Belfort results were:
72.3°F Dry Bulb/59.0°F Wet Bulb giving: Humidity 45% Dew Point 50°F
Davis SHT31:
72.3°F 43% DP: 49°F
SHT75:
72.3°F 42% DP: 48°F
Not necessarily surprising after 10hrs at 220°F. I then put the sensors outside in what has been near saturation conditions. I expected the sensors to carry a dry bias at high humidity. Surprisingly, I found the opposite.
Before the bake, I could not get the SHT31 above 98%. Now it goes to 100% and actually stays there. Not the "Sensirion jump" to 100% for one update cycle. The SHT75 before the bake would get to 98% and stay there with a jump periodically to 99 or 100%. Now it goes to 99% and stays there. It will jump to 100% but not sustain it like the 31.
Obviously the real test will be as conditions dry out. Unfortunately, that happens infrequently here this time of year. We've only gotten as low as the 80%s and there are signs of the SHT75 drying out better, but only by a percent or two and when you consider it being 1% low at 100%, I would say that's negligible.
Just thought I'd pass along as I was surprised by the high humidity results. I have a feeling that if it does dry out, I will be right back to where I was before the bake with all this high humidity, but if we get a dry day, I'll post the results.
How are the results going so far with your baked sensors?
I'd bake the old one, compare it to it's "pre-baked" old self and leave the new one untouched, at least for now to compare.I’m thinking about baking a old SHT-31 sensor. But I’m beginning to think that if I bought a new one, baking it before installing it would ensure me that any offset that the sensor has would be rid of.So I decided to do a little holiday baking ... with my temp/hum sensors. My hope was to remove the wet bias in drier conditions but also found surprisingly better performance at saturation after the bake.
I have a new Davis SHT31 (which I believe was manufactured in June 2019) that I've reported on in this forum with disappointing results. I also have a few SHT75s. I baked them all per Sensirion's datasheet for 10hrs at 220°F. I did not bother with the rehydration procedure because it's the Puget Sound in December ... they will get plenty of hydration.
The SHT75 I used for the test had been outside for about 9mos. When I brought it in it read about 4% high at room temperature compared to my Belfort pyschrometer @ 40% RH. The new Davis SHT31 has been inside aside from a week of testing outside a few weeks ago. It was 6% high and +3°F dew point compared to the Belfort even having been acclimated to the dry conditions of a heated house.
After baking I tested them against a Belfort psychrometer at room temperature. Temperature results were so accurate at 72°F among all sensors that there is nothing to note.
The Belfort results were:
72.3°F Dry Bulb/59.0°F Wet Bulb giving: Humidity 45% Dew Point 50°F
Davis SHT31:
72.3°F 43% DP: 49°F
SHT75:
72.3°F 42% DP: 48°F
Not necessarily surprising after 10hrs at 220°F. I then put the sensors outside in what has been near saturation conditions. I expected the sensors to carry a dry bias at high humidity. Surprisingly, I found the opposite.
Before the bake, I could not get the SHT31 above 98%. Now it goes to 100% and actually stays there. Not the "Sensirion jump" to 100% for one update cycle. The SHT75 before the bake would get to 98% and stay there with a jump periodically to 99 or 100%. Now it goes to 99% and stays there. It will jump to 100% but not sustain it like the 31.
Obviously the real test will be as conditions dry out. Unfortunately, that happens infrequently here this time of year. We've only gotten as low as the 80%s and there are signs of the SHT75 drying out better, but only by a percent or two and when you consider it being 1% low at 100%, I would say that's negligible.
Just thought I'd pass along as I was surprised by the high humidity results. I have a feeling that if it does dry out, I will be right back to where I was before the bake with all this high humidity, but if we get a dry day, I'll post the results.
How are the results going so far with your baked sensors?
How are the results going so far with your baked sensors?
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
I’m baking an older SHT 31 with the black coating and see how it does. Planning on installing it in my remote unit tomorrow morning as long it’s not raining. You can view data from that 31 here:
https://www.wunderground.com/dashboard/pws/KALTHORS2?cm_ven=localwx_pwsdash
I’ll let everyone know when the 31 goes live. Right now, I have the 75 installed.
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
Oooh sounds like someone may be bound to an NDA and have some test hardware. How exciting.
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
Curious where did you order the clear potting sensor from? Davis or Ryan at Scaled?
How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
Curious where did you order the clear potting sensor from? Davis or Ryan at Scaled?
BTW. How quick did your baked 31 go up to 100%?
You should actually compare dew points. I've seen as much as a 4% difference between stations when they show the same temp and dew point due to the particular spread at that time. Humidity AFAIC is only worth watching when very high or very low.96% humidity day/night. Today is 42% Humidity and sunny day, and has been +/- 2% to the NWS ASOS 2.6 miles away since online, and currently am 2% below the NWS ASOS, so fingers crossed wet bias does not rear its head.How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
Curious where did you order the clear potting sensor from? Davis or Ryan at Scaled?
Hopefully it didn't emit any of the dreaded VOC's.... 8-[Shouldn’t left the filter cap on when I baked it. lol. It melted some.How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
I’m baking an older SHT 31 with the black coating and see how it does. Planning on installing it in my remote unit tomorrow morning as long it’s not raining. You can view data from that 31 here:
https://www.wunderground.com/dashboard/pws/KALTHORS2?cm_ven=localwx_pwsdash
I’ll let everyone know when the 31 goes live. Right now, I have the 75 installed.
Thanks for the tip.You should actually compare dew points. I've seen as much as a 4% difference between stations when they show the same temp and dew point due to the particular spread at that time. Humidity AFAIC is only worth watching when very high or very low.96% humidity day/night. Today is 42% Humidity and sunny day, and has been +/- 2% to the NWS ASOS 2.6 miles away since online, and currently am 2% below the NWS ASOS, so fingers crossed wet bias does not rear its head.How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
Curious where did you order the clear potting sensor from? Davis or Ryan at Scaled?
Good. Always check the time of the stations your comparing to as dew points can vacillate quite a bit compared to the more steady temp.
Not disagreeing with anything you've said (ASOS's averaging algorithm is just part of thing we must deal with when comparing) except, I've seen the ASOS at TUS report 99% more times than I can count. 98%, not sure, but definitely 99.Good. Always check the time of the stations your comparing to as dew points can vacillate quite a bit compared to the more steady temp.you never see a NWS ASOS report 98% or 99% humidity.
Not disagreeing with anything you've said (ASOS's averaging algorithm is just part of thing we must deal with when comparing) except, I've seen the ASOS at TUS report 99% more times than I can count. 98%, not sure, but definitely 99.Good. Always check the time of the stations your comparing to as dew points can vacillate quite a bit compared to the more steady temp.you never see a NWS ASOS report 98% or 99% humidity.
TUS. They're only 4 miles apart, but DMA will always hit 100% before TUS will. TUS will eventually get there, but in the mean time, it'll sit on 99%. Whether DMA will display 99%, I honestly can't say, but you now have me looking.Not disagreeing with anything you've said (ASOS's averaging algorithm is just part of thing we must deal with when comparing) except, I've seen the ASOS at TUS report 99% more times than I can count. 98%, not sure, but definitely 99.Good. Always check the time of the stations your comparing to as dew points can vacillate quite a bit compared to the more steady temp.you never see a NWS ASOS report 98% or 99% humidity.
Interesting. TUS or DMA?
Hopefully it didn't emit any of the dreaded VOC's.... 8-[Shouldn’t left the filter cap on when I baked it. lol. It melted some.How are the results going so far with your baked sensors?
Unfortunately I can’t go into detail at the moment due to not having the time and I will follow up with more info as I’m able, but I’ve baked (another) brand new Davis 31 with positive results. Sensor goes to 100% AND this one follows the SHT75 when humidity drops which I’ve never seen before. This one has a clear potting not the black potting which my other “new” sensor had. I don’t know if that is part of the reason for the difference. The clear potting WILL MELT at 220F. It won’t turn completely into a liquid, but you have to be careful. More to follow as I’m able, but I’m cautiously optimistic from what I’ve seen so far and as you know I’ve been pretty critical ...
I’m baking an older SHT 31 with the black coating and see how it does. Planning on installing it in my remote unit tomorrow morning as long it’s not raining. You can view data from that 31 here:
https://www.wunderground.com/dashboard/pws/KALTHORS2?cm_ven=localwx_pwsdash
I’ll let everyone know when the 31 goes live. Right now, I have the 75 installed.
Here is 01JAN19 for both. This is what I'm used to seeing with how the NWS ASOS rounds.I am familiar. I compare here for ease but all the data is rounded compared to Meso. However, this page doesn't update timely until after business hours in the States...as stupid as that is... :roll: but obviously still comparable.
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?product=&past=1&stn=KDMA&unit=0&time=LOCAL&day1=2&month1=01&year1=2019&hour1=0
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?product=&past=1&stn=KTUS&unit=0&time=LOCAL&day1=2&month1=01&year1=2019&hour1=0
To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
Rain itself does not necessarily equate to full saturation, as a matter of fact, usually doesn't.To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Funny thing is, I specifically remember calling Sensirion (I think in San Fran) when I went from an 11 to the 15 and asked the "spoke person" if I needed to "bake" my 15 for proper operation and got a resounding "no". So much for that... :roll:
Thanks for the work.
To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Rain itself does not necessarily equate to full saturation, as a matter of fact, usually doesn't.To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Within a day or two. It did take a little time for it to rehydrate a little, so it was initially slow to come up, but once it did, it hit 100% like never before. But we have lots of saturated conditions here in fog and mist this time of year. It's been raining for hours here right now and it is at 95%, so as CW2274 says, rain doesn't necessarily mean saturated air.
To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Within a day or two. It did take a little time for it to rehydrate a little, so it was initially slow to come up, but once it did, it hit 100% like never before. But we have lots of saturated conditions here in fog and mist this time of year. It's been raining for hours here right now and it is at 95%, so as CW2274 says, rain doesn't necessarily mean saturated air.
Gotcha. It’s up to 99% now.
Great to hear. My baked SHT75 generally gets to 100% quicker. But that they both get there at all with consistency is a win for me.To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Within a day or two. It did take a little time for it to rehydrate a little, so it was initially slow to come up, but once it did, it hit 100% like never before. But we have lots of saturated conditions here in fog and mist this time of year. It's been raining for hours here right now and it is at 95%, so as CW2274 says, rain doesn't necessarily mean saturated air.
Gotcha. It’s up to 99% now.
Now it’s flipping back and forth from 99% to 100%. I like it.
Other than not pulling the 100% trigger, I'm still pleased with this sensor's overall performance. I considered the next time I pulled the ISS into the house I'd bake the sensor...but the problem with that is I have zero idea how long it would be before I see a "100%" day. The sensor could be completely back to "normal" by then. Oh well..Unfortunately, probably not helpful for folks like CW2274 who see extreme low humidity.To follow up on more details of my holiday baking, the Davis SHT31 that I originally baked would get to 100% after the bake as I've described. The SHT75 I baked did the same. The SHT31 before would only get to 98%. As humidity dropped into the 80s and 70s, the Davis 31 started to show a wet bias compared to the SHT75 by about 3%. This was consistent with what I have been frustrated with with these Davis sensors. This sensor had black potting and I believe it was manufactured in June 2019.
I got another Davis 31 with clear potting that I believe was manufactured in November 2019. Before the bake, this sensor ran high on humidity at room temperature like all the rest. After the bake, it performed significantly better at room temperature. After the bake it also consistently hit 100%. Most importantly, this sensor will follow the SHT75 almost exactly as the humidity dries out into the 70s. Unfortunately I haven't seen below that. I have never seen a Davis 31 follow the 75. It almost always has a high bias as it dries out, so this is significant to me. I have one more sensor coming and will follow up. I will also follow up if I see lower humidity levels or if I test the current one inside.
With this next sensor I plan to try to shield the potting better during the bake if it is the clear potting as it does melt some. If anyone plans on baking theirs with clear potting, be sure to be careful about the melting. I may simply try to wrap most of the next one in aluminum foil. I should have mentioned that I do remove the filter for baking (sorry jgentry). If this new sensor has black potting I will probably return it.
No problem. Lol. How fast does the baked sensor goes up to 100%? It has been raining all day and my remote station with the baked sensor has peaked at 98% so far.
Within a day or two. It did take a little time for it to rehydrate a little, so it was initially slow to come up, but once it did, it hit 100% like never before. But we have lots of saturated conditions here in fog and mist this time of year. It's been raining for hours here right now and it is at 95%, so as CW2274 says, rain doesn't necessarily mean saturated air.
Gotcha. It’s up to 99% now.
Now it’s flipping back and forth from 99% to 100%. I like it.
Thanks
So you bake the whole circuit board in the oven?
Or do you unsolder the sensor and bake?
what do you place on, cookie sheet or something?
I followed the info in a prior post which said a temp. of 220F for 10 hours. I have been doing mine in a toaster over, got the temp set with a thermometer and it worked from about 215 to 225 degrees and has worked out real well.
Finally had an extreme drop in humidity today after weeks of high humidity. Raw humidity for both my baked Davis 31 and SHT75 reached 26%. I have never seen the Davis 31 match the SHT75 at humidity levels this low. My Cumulus correction is likely excessive at this humidity level, the total correction I was using was -5%. Normally for my sensors about -5% for humidity in the mid to low 20s is about right compared to my Belfort and to match nearby ASOS stations.
To compare with ASOS, my raw data at 555p was:
Temp: 59°F Hum: 27% DP: 25°F
KTIW at 553p:
Temp: 59°F Hum: 28% DP: 26°F
KSEA at 553p:
Temp: 61°F Hum: 24% DP: 24°F
My raw data for these sensors never compares well to these ASOS stations at this low humidity especially after long periods near saturation.
Here is the calibrated data for my station that is maybe overcorrected:
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?product=&past=1&stn=C7491&unit=0&time=LOCAL&day1=3&month1=01&year1=2020&hour1=18
To get 100% after the bake and now this kind of performance at the low end from a Davis 31 is really welcome news to me. I hope it continues and isn't an anomaly.
The 31 you’re talking here is the one with the clear potting and not the black one right?
Good results I just wonder how long it will last?That is the question isn't it? I'm cautiously optimistic based on yesterday's humidity drop. The Davis 31 I am using now has been baked and outside in near saturated air for 2 weeks. I've never seen the raw data match the SHT75 or ASOS even after previous bakes, but I've been disappointed with these things before ... I would not be surprised to see it no longer hit 100% and/or for the high humidity bias to return.
The 31 you’re talking here is the one with the clear potting and not the black one right?
That's correct. Another Davis 31 came yesterday. It also has clear potting. Manufacture date also looks like November 2019. I baked it last night wrapped in aluminum foil with just the actual sensor exposed. Worked great. No melting. I will post the pre and post bake results later. I've actually put the other clear baked Davis 31 as my main sensor now. It has a -2% offset and then a Cumulus calibration of (1.021x-2). This produces a -2% correction at the top of the scale and max -4% correction at the lower end of the scale. I may take the Cumulus calibration out completely as I see how it performs. The SHT75 I was using as my main sensor is still outside for comparison. My CWOP ID is CW7491 of course for those that want to see how this baked Davis 31 does
Even without a fan, I'd think particulates will eventually get into that tiny sensor hole without some kind of filter.I have no filter over it and the sensor is receiving good airflow in a passive shield.The 31 you’re talking here is the one with the clear potting and not the black one right?
That's correct. Another Davis 31 came yesterday. It also has clear potting. Manufacture date also looks like November 2019. I baked it last night wrapped in aluminum foil with just the actual sensor exposed. Worked great. No melting. I will post the pre and post bake results later. I've actually put the other clear baked Davis 31 as my main sensor now. It has a -2% offset and then a Cumulus calibration of (1.021x-2). This produces a -2% correction at the top of the scale and max -4% correction at the lower end of the scale. I may take the Cumulus calibration out completely as I see how it performs. The SHT75 I was using as my main sensor is still outside for comparison. My CWOP ID is CW7491 of course for those that want to see how this baked Davis 31 does
Even without a fan, I'd think particulates will eventually get into that tiny sensor hole without some kind of filter.I have no filter over it and the sensor is receiving good airflow in a passive shield.The 31 you’re talking here is the one with the clear potting and not the black one right?
That's correct. Another Davis 31 came yesterday. It also has clear potting. Manufacture date also looks like November 2019. I baked it last night wrapped in aluminum foil with just the actual sensor exposed. Worked great. No melting. I will post the pre and post bake results later. I've actually put the other clear baked Davis 31 as my main sensor now. It has a -2% offset and then a Cumulus calibration of (1.021x-2). This produces a -2% correction at the top of the scale and max -4% correction at the lower end of the scale. I may take the Cumulus calibration out completely as I see how it performs. The SHT75 I was using as my main sensor is still outside for comparison. My CWOP ID is CW7491 of course for those that want to see how this baked Davis 31 does
So far, I’m still liking the results of the baked sensor. Anybody else still liking their results?
Anyone still having good results with the baked sensor?
Well i haven't updated in a while because the new 31 that i was testing went belly up after only two months and i was in mourning for some time because i took a chance and did a little reshaping of the board to fit my passive shield and thus no warranty. I just got a new 31 in yesterday and after wrapping it in a wet wash cloth for some time it seems to max out at only 96%. I put it outside last night so i could compare it with three other sensors i am testing and this morning the 3 sensors showed one at 92% and the other two at 91% while the new 31 was showing 86%, just lousy reading. I am now baking it to see if it will get back on track with a good reading. Will report tomorrow if it is going back to Ryan for another one.
Not sure if this has been asked. When you bake your sensor, do you put the wires and all in oven or take them off.
Chuck
I believe I have an SHT15. I bought my station around 2013 or 2014 I believe. Would I be better off getting an SHT31?If you bought it new and have not modified it, you have an SHT11. The 31 is a superior sensor, problem aside, which has "seemingly" been addressed. Personally, I would spring for a 31. If you do, don't forget the -0.9F offset for the temperature.
Noticed that the Davis EnviroMonitor can take I2C sensors
https://www.davisinstruments.com/product_documents/weather/EM-sensors.pdf
Another update sensor still working fine, had dense fog this am and sensor hit solid 99% and no sign of wet bias so far.This one you threw in the Easy Bake Oven, right?
baking made it work much better.I just use my climate. ;)
Im new here on the forum, and am having to replace my humidity sensor in my VP2 as mine started reporting bad data. Ive tried to track through this long thread to get some info but its so long. Anyone care to give me a synopsis of the SHT-31 sensor? Is this a bad sensor? Good sensor? is the reliability poor? Im coming into this blind. Looking at my historical data it seems my snesor began going bad just 3 months or so after I bought my VP2 brand new. It is a 2017 unit so it came with the newer SHT-31 sensor. It reports humidty 10-20% too low compared to other stations. Today its reporting 73% and airport 20 miles away reporting 95% . Rain is looming today so very humid and cloudy. My new sensor arrives tomorrow and I will be installing it. Trying to gain some knowledge that may be helpful.
Im new here on the forum, and am having to replace my humidity sensor in my VP2 as mine started reporting bad data. Ive tried to track through this long thread to get some info but its so long. Anyone care to give me a synopsis of the SHT-31 sensor? Is this a bad sensor? Good sensor? is the reliability poor? Im coming into this blind. Looking at my historical data it seems my snesor began going bad just 3 months or so after I bought my VP2 brand new. It is a 2017 unit so it came with the newer SHT-31 sensor. It reports humidty 10-20% too low compared to other stations. Today its reporting 73% and airport 20 miles away reporting 95% . Rain is looming today so very humid and cloudy. My new sensor arrives tomorrow and I will be installing it. Trying to gain some knowledge that may be helpful.
Humidity is only relative to the temperature so saying your humidity is running low doesn't give a full picture of what's really going on. Where is the dewpoint in relation to the airport? Like I said these SHT31 sensors run higher than airports is my experience so if anything they have a wet bias. This was the reason I was asking for a link to your station.
Im new here on the forum, and am having to replace my humidity sensor in my VP2 as mine started reporting bad data. Ive tried to track through this long thread to get some info but its so long. Anyone care to give me a synopsis of the SHT-31 sensor? Is this a bad sensor? Good sensor? is the reliability poor? Im coming into this blind. Looking at my historical data it seems my snesor began going bad just 3 months or so after I bought my VP2 brand new. It is a 2017 unit so it came with the newer SHT-31 sensor. It reports humidty 10-20% too low compared to other stations. Today its reporting 73% and airport 20 miles away reporting 95% . Rain is looming today so very humid and cloudy. My new sensor arrives tomorrow and I will be installing it. Trying to gain some knowledge that may be helpful.
Humidity is only relative to the temperature so saying your humidity is running low doesn't give a full picture of what's really going on. Where is the dewpoint in relation to the airport? Like I said these SHT31 sensors run higher than airports is my experience so if anything they have a wet bias. This was the reason I was asking for a link to your station.
As of right now.
Airport:
TEMP: 61F
Dew Point: 56
Humidity: 84%
Pressure: 30.12
Ambient Weather WS-2902 3 miles from my station:
TEMP: 64F
Dew Point: 59
Humidity: 85%
Pressure: 30.17
My Station:
TEMP: 64F
Dew Point: 51
Humidity: 64%
Pressure: 30.15
The airport is ~20 miles north of me, and a cold front is approaching with lots of rain. The temperature difference is accurate and is reflected by all the weather stations in a 60 mile radius. The humidity im reporting (64%) is a lot lower than everyone right now. Dew Point obviously a little off as well. So dew point/humidty are innacurate. My temperature however is very accurate and has had no issues from what I can tell.
Well we just got through with a strong high pressure system behind a cold front and the humidity of my 31 and my 15 both hit 18% which is very low for me down here and the new 31 has been doing real well from bottom to top on readings and still no sign of wet bias. \:D/
Well we just got through with a strong high pressure system behind a cold front and the humidity of my 31 and my 15 both hit 18% which is very low for me down here and the new 31 has been doing real well from bottom to top on readings and still no sign of wet bias. \:D/
But I’m beginning to think that the Sensirion filter keeps the sensor from having a wet bias longer than the silk “filter.”As Sensirion states, the SF2 cap, if properly installed, is a water tight solution that "consists of a single piece of PBT and an integrated water vapor-permeable filter membrane." I doubt silk was designed as such.
I have been comparing HYT221 and SHT21 for about 6 months now. Lately, HYT221 started to have significant wet bias, if the real humidity level is above 70%. This means that if the near official station and SHT21 think the humidity is about 80%, HYT221 can show that RH is more than 90%. However, if the humidity is less than 70%, both SHT21 and HYT221 have similar readings. Actually, HYT221 is very close to the official station, if the humidity is around 20%-40%, while SHT21 has a slight wet bias all the time.
It is worth of mentioning that it has not rained or there has not been fog/frost for weeks now. Both sensors are now installed in the same radiation shield and HYT221 has no more a DIY plastic splash cover (but of course it has its own yellowish filter). I have no idea why HYT221 has started to act like this. In the winter, it performed very well. Also, HYT221 has +0.4 Celsius warm bias at cold temperatures (if outdoor temperature is less than 0 Celsius) compared to the SHT21. I trust SHT21 temperatures more, since I have other thermometers as well and they agree with SHT21.
In conclusion, SHT31 and HYT221 both failed within one winter. SHT31 has near constant -10% dry bias, HYT221 has +10% wet-bias at high humidity levels and SHT21 has not-so-bad wet-bias. I really consider buying a Vaisala sensor to stop this nightmare...
even in fog mist my station only got to 96%.Well, I suppose you could try the "baking method" if you wanted.
Thanks. overall am happy as has been smooth operation. dialing in is the next chapter."Dialing in" humidity is almost always a two way street..rob Peter to pay Paul. You may fix one end, but trash the other. Then again, here I see the full range from 1% to 100%, so perhaps you can get it where you want it more so than I.
To be honest the baking the sensor process makes me nervous am going to damage the sensor.
If a mishap happens can always replace the sensor :).
What tips for baking do you have and I read a toaster oven is an option?
The analog sensor in the WMII after good cleaning is working very well and on this same fog mist morning hit 100% for several hours. Impressed that after all these years still working accurately.Yes, the old analog sensors seem to have little trouble pulling the 100% trigger unlike the current digital batch. No idea how they did/do in the other extreme. Being so old, there may be some drift to watch for if you care.
Sorry to break in to the conversation but I was hoping someone could point me in the right direction to the instructions on how to bake the 31 as so many have successfully accomplished. Thanks.
Great idea, not sure I want to buy a toaster oven just for this though.Celebrate afterwards with some tater tots...
I thought about starting a new topic, but thought the input keeps with the continuity of this original topic.
I recently compared the SHT85 with the SHT75 in my Davis VP2 as well as a Davis mounted SHT31. I was able to get the data from the SHT85 with an old USB test kit I had from Sensirion and their RS485 Sensor Viewer 2.91 software. The siting of the SHT85 was not desirable due to cable length restrictions, but the sensor comes with its own sensor-mounted filter and I placed it in the Davis 7714 radiation shield. If temperatures between the sensors were the same, I was able to compare humidity values directly. In times when they weren't, I used dewpoint.
Initially, the SHT85 data seemed promising, running 6-8 percentage points lower in humidity than the SHT75 (2-3°F lower in dewpoint). Even after a period of high humidity, where both sensors reached 98%, the SHT85 would read a lower humidity when the air dried out again. Unfortunately, after a longer period of high humidity, the high humidity bias presented itself in the SHT85 and pretty much matched the SHT75 exactly. After the test, I brought the high bias SHT85 and SHT75 inside to compare with the Davis-mounted SHT31 which I have baked previously and has been inside in low humidity. Both the SHT75 and SHT85 perform about the same or a little better even with the high humidity bias present.
Just to add to the mix i have an old 31 that i had out for some time and it showed the bias of 3% high which is keeping with the specs of the sensor which is the sensor will read high after being in a high humidity setting of more than 80% for three days are more and will only return to the normal reading after being below the 80% for some time as it says the return will be very slow. I put the new 31 out and it has been very good with the low and high end readings with a lot of 100% readings in heavy fog. I put the 31 back out in a different shield and sure enough after a long period of drying out it read 1% lower than the new 31 and has been holding that for several weeks. We haven't got into a run of high humidity yet so won't know what happens until i get a good run of above 80% to set the stage for the error to show up. Now i think the baking works well because of the very low humidity in the oven and makes for a faster recovery time but just keeping it below 80% for sometime works the same just slower. This time of year i can get periods of above 80% for a week at a time so i will just have to wait for that to happen.
If you recall, the Acurite device that utilized the 31 had no bias compared to the Davis mounted 31. I kinda thought we were done with this fiasco. Yes, I know, I'm in the desert, but my current 31 is 18 months old and I remain very happy with it. I still think a sealed SF2 cap is a difference maker in the big scheme of things.Just to add to the mix i have an old 31 that i had out for some time and it showed the bias of 3% high which is keeping with the specs of the sensor which is the sensor will read high after being in a high humidity setting of more than 80% for three days are more and will only return to the normal reading after being below the 80% for some time as it says the return will be very slow. I put the new 31 out and it has been very good with the low and high end readings with a lot of 100% readings in heavy fog. I put the 31 back out in a different shield and sure enough after a long period of drying out it read 1% lower than the new 31 and has been holding that for several weeks. We haven't got into a run of high humidity yet so won't know what happens until i get a good run of above 80% to set the stage for the error to show up. Now i think the baking works well because of the very low humidity in the oven and makes for a faster recovery time but just keeping it below 80% for sometime works the same just slower. This time of year i can get periods of above 80% for a week at a time so i will just have to wait for that to happen.
I’m curious if the 31 was mounted correctly, it would return back into calibration quicker than the Davis’ setup?
You certainly can be done with the fiasco if you wish, I just was providing input for anyone who is interested in the SHT85. For those of us in humid climates, the fiasco is real. The SHT85 is a Sensirion mounted SHT35 with a PTFE membrane right on the sensor. Unfortunately the 85 performs exactly like the SHT75 in a humid climate despite the hope it might do better. And yes, the one thing that hasn’t changed is in my experience and climate, the SHT75 and 85 are superior to the Davis mounted 31.I quoted and replied to 'jgentry'...not you.
Understood. It’s an open forum and I’m replying to you.Fine. My response was not meant for your issues as I have zero experience with either the 75 or 85. My "fiasco" comment was strictly meant in regards to the 31 issue, which I have plenty of experience with.
If you recall, the Acurite device that utilized the 31 had no bias compared to the Davis mounted 31. I kinda thought we were done with this fiasco. Yes, I know, I'm in the desert, but my current 31 is 18 months old and I remain very happy with it. I still think a sealed SF2 cap is a difference maker in the big scheme of things.Just to add to the mix i have an old 31 that i had out for some time and it showed the bias of 3% high which is keeping with the specs of the sensor which is the sensor will read high after being in a high humidity setting of more than 80% for three days are more and will only return to the normal reading after being below the 80% for some time as it says the return will be very slow. I put the new 31 out and it has been very good with the low and high end readings with a lot of 100% readings in heavy fog. I put the 31 back out in a different shield and sure enough after a long period of drying out it read 1% lower than the new 31 and has been holding that for several weeks. We haven't got into a run of high humidity yet so won't know what happens until i get a good run of above 80% to set the stage for the error to show up. Now i think the baking works well because of the very low humidity in the oven and makes for a faster recovery time but just keeping it below 80% for sometime works the same just slower. This time of year i can get periods of above 80% for a week at a time so i will just have to wait for that to happen.
I’m curious if the 31 was mounted correctly, it would return back into calibration quicker than the Davis’ setup?
That may or may not be true. However, with an SF2 cap that is properly sealed, it is a water tight solution that only allows water vapor to penetrate. That an a case fan should alleviate any potential moisture build up over ambient AFAIC. One thing for certain, I'll never go without an SF2 cap again.If you recall, the Acurite device that utilized the 31 had no bias compared to the Davis mounted 31. I kinda thought we were done with this fiasco. Yes, I know, I'm in the desert, but my current 31 is 18 months old and I remain very happy with it. I still think a sealed SF2 cap is a difference maker in the big scheme of things.Just to add to the mix i have an old 31 that i had out for some time and it showed the bias of 3% high which is keeping with the specs of the sensor which is the sensor will read high after being in a high humidity setting of more than 80% for three days are more and will only return to the normal reading after being below the 80% for some time as it says the return will be very slow. I put the new 31 out and it has been very good with the low and high end readings with a lot of 100% readings in heavy fog. I put the 31 back out in a different shield and sure enough after a long period of drying out it read 1% lower than the new 31 and has been holding that for several weeks. We haven't got into a run of high humidity yet so won't know what happens until i get a good run of above 80% to set the stage for the error to show up. Now i think the baking works well because of the very low humidity in the oven and makes for a faster recovery time but just keeping it below 80% for sometime works the same just slower. This time of year i can get periods of above 80% for a week at a time so i will just have to wait for that to happen.
I’m curious if the 31 was mounted correctly, it would return back into calibration quicker than the Davis’ setup?
I’m sure the cap helps. But I think the big issue is that the sensor isn’t getting maximum airflow, which causes moisture to collect for long periods of time and permanently offset the sensor.
Not directly relevant, but I see that the Sensirion SHT4x series are starting to becoming available:
https://www.sensirion.com/en/environmental-sensors/humidity-sensors/humidity-sensor-sht4x/
Just SHT40 so far, but 41 and 45 apparently due later this year. Adafruit have stock of the SHT40 (true) I2C version in a STEMMA board:
https://www.adafruit.com/product/4885
Absolutely no word or hint from Davis about any changes, so this is just for general background info.
You'll likely never be able to run anything other than the SHT31 with Davis VP2. Unless Davis comes out with a new ISS.
CW, how did you modify your SF2 cap to work on the SHT31 Davis PCB?I wasn't thrilled about the glue option so I trimmed the four feet down to be flush with the base and used very thin stainless steel wire to wrap around the cap and cinch it down with pliers twisting from the back side. The wire doesn't come in contact with the membrane but arches over. With the "gooey" substance that surrounds the sensor it allows the cap to seat firmly in what I believe is a true seal.
Not directly relevant, but I see that the Sensirion SHT4x series are starting to becoming available:
https://www.sensirion.com/en/environmental-sensors/humidity-sensors/humidity-sensor-sht4x/
Just SHT40 so far, but 41 and 45 apparently due later this year. Adafruit have stock of the SHT40 (true) I2C version in a STEMMA board:
https://www.adafruit.com/product/4885
Absolutely no word or hint from Davis about any changes, so this is just for general background info.
Is it high humidity or high dew point? If it's 0F outside and a dew point of -1F, that's 98ish% humidity, but bone dry air. I'm thinking high dew is the culprit, it's not fond of being "wet".Not directly relevant, but I see that the Sensirion SHT4x series are starting to becoming available:
https://www.sensirion.com/en/environmental-sensors/humidity-sensors/humidity-sensor-sht4x/
Just SHT40 so far, but 41 and 45 apparently due later this year. Adafruit have stock of the SHT40 (true) I2C version in a STEMMA board:
https://www.adafruit.com/product/4885
Absolutely no word or hint from Davis about any changes, so this is just for general background info.
My biggest pet peeve about the Sensirion sensor (and I’ve heard others do the same) is that after being exposed to humidities over 80% for a long period of time, it goes out of calibration until it recalibrates itself.
it also mentions extreme low humidity for prolonged periods will introduce a low bias, which hasn’t been discussed because most of us probably don’t experience it.Good post, I didn't know this. Obviously I do experience regular extreme low humidity, and sure enough, when I get to the 4% or lower range it starts to get a little over the top with tanking dew points, especially down at 1%, but even I don't get that but a few days a year.
CW, how did you modify your SF2 cap to work on the SHT31 Davis PCB?I wasn't thrilled about the glue option so I trimmed the four feet down to be flush with the base and used very thin stainless steel wire to wrap around the cap and cinch it down with pliers twisting from the back side. The wire doesn't come in contact with the membrane but arches over. With the "gooey" substance that surrounds the sensor it allows the cap to seat firmly in what I believe is a true seal.
One of the things I noticed in the SHT4X datasheet is an onboard heater. This is incorporated into the SHT3X as well, but the SHT4X datasheet specifically mentions one of the functions of the heater is for condensing environments to eliminate creep, which is the name they give to the high bias we see and they mention in prolonged high humidity. They also mention that there will be dedicated application notes elaborating on the use of the heater for this purpose.
It would be interesting if this function could be utilized so the Sensirion sensor was used to calculate and output dew point and then incorporate a separate temperature measuring element (thermally isolated from any self-heating), maybe a standard thermistor, for air temperature. The console could then calculate RH based on the two temperatures instead of calculating dew point. I posted a bit ago about a new version .80 temp/hum sensor Rainwise uses for their MKIII that I was speculating might actually do this as it appears to have both a thermistor and a Sensirion sensor on their temp/hum board
The wax holds moisture and keeps the sensor from fully “drying” out.I really can't see that. If anything, wax is hydrophobic. That's why you put it on your car's finish for example.
The wax holds moisture and keeps the sensor from fully “drying” out.I really can't see that. If anything, wax is hydrophobic. That's why you put it on your car's finish for example.
CW, how did you modify your SF2 cap to work on the SHT31 Davis PCB?I wasn't thrilled about the glue option so I trimmed the four feet down to be flush with the base and used very thin stainless steel wire to wrap around the cap and cinch it down with pliers twisting from the back side. The wire doesn't come in contact with the membrane but arches over. With the "gooey" substance that surrounds the sensor it allows the cap to seat firmly in what I believe is a true seal.
All I use is braided wire that one might use to hang a picture with. It has like twenty or so strands and I peel off three of them. It's strong enough not to break when cinching it down (judgement required here, have extra ;)) while snugging down the cap without covering too much membrane.CW, how did you modify your SF2 cap to work on the SHT31 Davis PCB?I wasn't thrilled about the glue option so I trimmed the four feet down to be flush with the base and used very thin stainless steel wire to wrap around the cap and cinch it down with pliers twisting from the back side. The wire doesn't come in contact with the membrane but arches over. With the "gooey" substance that surrounds the sensor it allows the cap to seat firmly in what I believe is a true seal.
CW, do you have a source for the stainless wire you used?
BTW, if you were unaware, Sensirion advises not to touch the membrane itself. I used small needle nose pliers to center the cap. It can be a little tricky...
BTW, if you were unaware, Sensirion advises not to touch the membrane itself. I used small needle nose pliers to center the cap. It can be a little tricky...
Good, hopefully it wasn't too much of a pain. Are you going to use the stock filter as well? The reason I ask is that the SF2 has done such an outstanding job by itself, I haven't been out to service my ISS in over a year and a half and I know the sensor chamber is layered in dust/dirt from the case fan. That's three times longer than I have ever gone because the cap does such a good job that I see absolutely no degradation in sensor performance. That said, I was thinking of adding the stock filter to slow, yes I said slow, the response time in the summer heat. But that means climbing over my wall and out to the desert to service the ISS more like I use to. Ahhh, decisions...BTW, if you were unaware, Sensirion advises not to touch the membrane itself. I used small needle nose pliers to center the cap. It can be a little tricky...
Installed the CAP yesterday. So far so good. I did a bake and then a refrigeration on a fresh sensor. Waiting for high humid days to see how well this mod works.
I think is why most official stations use some sort of averaging algorithm for temperature.They all do (at least ASOS's) and not just temp, but other parameters as well. If they didn't, then the data would potentially be all over the place just like a PWS, so they "even it out."
Yeah, if you can work it out, I don’t think the SF2 inside the stock filter will cost you much in response time with the fan.What I'm trying to help alleviate is the wild temp swings that I see during max insolation as the heat eddies across the desert floor. With a 60CFM fan, those are sucked up like nobody's business. I have a 40CFM backup, but am not inclined to swap them at this time. When the stock filter starts to "dirty up", maybe I'll be more satisfied. Yep, dirtier may be better...well at least for me.
I also thought this was an interesting read. Especially that even Campbell Scientific is frustrated that all humidity sensors aren’t fundamentally designed for meteorological applications ...Good read. Humidity has always been the "rub" in sensors, but by far in the extremes.
https://www.campbellsci.com/blog/air-temp-rh-sensors-need-to-know
I also thought this was an interesting read. Especially that even Campbell Scientific is frustrated that all humidity sensors aren’t fundamentally designed for meteorological applications ...
https://www.campbellsci.com/blog/air-temp-rh-sensors-need-to-know
Not that it isn't frustrating, but as always, ya pay to play folks. Davis sees it as 99.9% satisfaction rate to their "basic" customer. If you want better, then move up and pay up. Simple as that.I also thought this was an interesting read. Especially that even Campbell Scientific is frustrated that all humidity sensors aren’t fundamentally designed for meteorological applications ...
https://www.campbellsci.com/blog/air-temp-rh-sensors-need-to-know
Yep. And the Sensirion 4x isn’t no better than its predecessors...
“ 2.3 Recommended Operating Conditions
The sensor shows best performance when operated within the recommended normal temperature and humidity range of 5 °C ... 60 °C and 20 %RH ... 80 %RH, respectively. Long term exposure to conditions outside recommended normal range, especially at high relative humidity, may temporarily offset the RH signal (e.g. +3 %RH after 60 h at > 80 %RH). After returning into the recommended normal temperature and humidity range the sensor will recover to within specifications by itself. Prolonged exposure to extreme conditions may accelerate ageing.”
Good, hopefully it wasn't too much of a pain. Are you going to use the stock filter as well? The reason I ask is that the SF2 has done such an outstanding job by itself, I haven't been out to service my ISS in over a year and a half and I know the sensor chamber is layered in dust/dirt from the case fan. That's three times longer than I have ever gone because the cap does such a good job that I see absolutely no degradation in sensor performance. That said, I was thinking of adding the stock filter to slow, yes I said slow, the response time in the summer heat. But that means climbing over my wall and out to the desert to service the ISS more like I use to. Ahhh, decisions...BTW, if you were unaware, Sensirion advises not to touch the membrane itself. I used small needle nose pliers to center the cap. It can be a little tricky...
Installed the CAP yesterday. So far so good. I did a bake and then a refrigeration on a fresh sensor. Waiting for high humid days to see how well this mod works.
Not that it isn't frustrating, but as always, ya pay to play folks. Davis sees it as 99.9% satisfaction rate to their "basic" customer. If you want better, then move up and pay up. Simple as that.I also thought this was an interesting read. Especially that even Campbell Scientific is frustrated that all humidity sensors aren’t fundamentally designed for meteorological applications ...
https://www.campbellsci.com/blog/air-temp-rh-sensors-need-to-know
Yep. And the Sensirion 4x isn’t no better than its predecessors...
“ 2.3 Recommended Operating Conditions
The sensor shows best performance when operated within the recommended normal temperature and humidity range of 5 °C ... 60 °C and 20 %RH ... 80 %RH, respectively. Long term exposure to conditions outside recommended normal range, especially at high relative humidity, may temporarily offset the RH signal (e.g. +3 %RH after 60 h at > 80 %RH). After returning into the recommended normal temperature and humidity range the sensor will recover to within specifications by itself. Prolonged exposure to extreme conditions may accelerate ageing.”
I just got a new VP2 with the 24 hour fan-aspirated shield. It's still in the box waiting for the frost to get out of the ground here in Kansas so it can be installed. I haven't seen, or may have missed, any mention of SF2 maintenance. I live in a rural area surrounded by grain fields. The air gets real dusty during planting and harvest seasons. I am considering getting an SF2 but was wondering what the dusty air will do to it. I have searched Sensirion's web site relative to maintenance but all I could find was handling requirements as mentioned in an above post. Can dust be removed with a soft brush or will it need to be replaced? Or will use of the stock filter over the SF2 be sufficient to keep the dust off of it?
I am considering getting an SF2 but was wondering what the dusty air will do to it.See reply #1655 up top.
Leave the actual sensor exposed while baking, but just be sure to protect the potting around the sensor during the bake to keep it from melting. Wrapping it in aluminum foil worked well for me.
Have you compared the graphs between your station and KTUS? If you’re not aware, you can get the raw 1 minute historical ASOS readings from here.Yeah, if you can work it out, I don’t think the SF2 inside the stock filter will cost you much in response time with the fan.What I'm trying to help alleviate is the wild temp swings that I see during max insolation as the heat eddies across the desert floor. With a 60CFM fan, those are sucked up like nobody's business. I have a 40CFM backup, but am not inclined to swap them at this time. When the stock filter starts to "dirty up", maybe I'll be more satisfied. Yep, dirtier may be better...well at least for me.
Yes I have, and I'm aware. Thank you.Have you compared the graphs between your station and KTUS? If you’re not aware, you can get the raw 1 minute historical ASOS readings from here.Yeah, if you can work it out, I don’t think the SF2 inside the stock filter will cost you much in response time with the fan.What I'm trying to help alleviate is the wild temp swings that I see during max insolation as the heat eddies across the desert floor. With a 60CFM fan, those are sucked up like nobody's business. I have a 40CFM backup, but am not inclined to swap them at this time. When the stock filter starts to "dirty up", maybe I'll be more satisfied. Yep, dirtier may be better...well at least for me.
I'll see how it goes with the new capUnderstood, however, the stock filter will do nothing to alleviate any potential bias, as it's merely still just that...the stock filter. The SF2 isn't and performs a much more protective roll.
I recently purchased two new sensors and they have been working just fine, both hit 100% and checked out just fine on low end. No sign so far of wet bias that i have seen.
This is the size i cut the sht31 down to compared to a nickel [ You are not allowed to view attachments ]
I’m interested to hear over time what people have resolved with the SHT31 issues. I know some have said they’ve seen an improvement in the newer Davis 31s. For those folks, do you still see improved performance as it relates to a wet bias and being able to reach 100% humidity in saturation? Have folks just accepted that the issues with the Davis 31 are what they are? Is anyone still using the SHT75 instead? I’m still using the SHT75 and periodically compare my Davis 31s (after baking the sensors etc) and still ultimately run into the same problems. I guess I’m wondering if the lack of activity in this thread over time is more a function of acceptance or a function of sensor improvement that jgentry and jerryg have noted.
I’m interested to hear over time what people have resolved with the SHT31 issues. I know some have said they’ve seen an improvement in the newer Davis 31s. For those folks, do you still see improved performance as it relates to a wet bias and being able to reach 100% humidity in saturation? Have folks just accepted that the issues with the Davis 31 are what they are? Is anyone still using the SHT75 instead? I’m still using the SHT75 and periodically compare my Davis 31s (after baking the sensors etc) and still ultimately run into the same problems. I guess I’m wondering if the lack of activity in this thread over time is more a function of acceptance or a function of sensor improvement that jgentry and jerryg have noted.
The new Davis SHT-31s finally showed the same ole wet bias issues. I thought they were resolved but I ended up being wrong. My SHT-31s did not reach to 100%. It only reached to 99%. I’m just forced to accept the errors. The WeatherFlow Tempest SHT-31 doesn’t have this problem except for one (no wet bias but started topping off at 95% after a few months of use).
The way Davis handles and mounts the sensor, it doesn’t take long for it to be out of calibration.
I’m interested to hear over time what people have resolved with the SHT31 issues. I know some have said they’ve seen an improvement in the newer Davis 31s. For those folks, do you still see improved performance as it relates to a wet bias and being able to reach 100% humidity in saturation? Have folks just accepted that the issues with the Davis 31 are what they are? Is anyone still using the SHT75 instead? I’m still using the SHT75 and periodically compare my Davis 31s (after baking the sensors etc) and still ultimately run into the same problems. I guess I’m wondering if the lack of activity in this thread over time is more a function of acceptance or a function of sensor improvement that jgentry and jerryg have noted.
The new Davis SHT-31s finally showed the same ole wet bias issues. I thought they were resolved but I ended up being wrong. My SHT-31s did not reach to 100%. It only reached to 99%. I’m just forced to accept the errors. The WeatherFlow Tempest SHT-31 doesn’t have this problem except for one (no wet bias but started topping off at 95% after a few months of use).
The way Davis handles and mounts the sensor, it doesn’t take long for it to be out of calibration.
Thanks jgentry. I was afraid of that …
Well I have psychro-dyne now which is pretty accurate and a new SHT-31 I always purchase the SI 25 foot 31's due to my custom station setup and I'm finding the dew point is either right on or reading low 1 degree not high. I only use dew point chasing humidity around is a waste of time. Anyway, the highest I've seen in DP is 71 and the lowest is around 48 so limited where I've checked but I no longer see those crazy high heat indices of old. Yes if you heavy aspirate it moves around a couple of degrees once the ambient gets above about 84 or so but if you don't heavily aspirate with a higher-powered AC fan the spiking movement is less.
Now yes it reads higher than the ASOS but it's correct where the ASOS is actually reading low humidity and actually is a POS itself they are force-feeding this warming by cranking the rural ASOS temperature up so it's hard to trust anything about it.
This crap started around March of 2017 the local official coop station happens to be run by the radio station owner in Valentine too so everyone pretty much knows what's up with the Valentine KVTN ASOS. Just a short example without getting into full detail about being above freezing during icing events, the ASOS inability to reach full saturation so now the max humidity is 94% the AP ASOS has had 9-100+ days while all the other local Wx stations including the COOP-3 this summer and it goes on and on. Really rock-solid case they are tampering with the temperatures on these FAA weather stations likely inserting a multiplier because the hotter it gets the wider the spread from other thermometers.
Well I have psychro-dyne now which is pretty accurate and a new SHT-31 I always purchase the SI 25 foot 31's due to my custom station setup and I'm finding the dew point is either right on or reading low 1 degree not high. I only use dew point chasing humidity around is a waste of time. Anyway, the highest I've seen in DP is 71 and the lowest is around 48 so limited where I've checked but I no longer see those crazy high heat indices of old. Yes if you heavy aspirate it moves around a couple of degrees once the ambient gets above about 84 or so but if you don't heavily aspirate with a higher-powered AC fan the spiking movement is less.
Now yes it reads higher than the ASOS but it's correct where the ASOS is actually reading low humidity and actually is a POS itself they are force-feeding this warming by cranking the rural ASOS temperature up so it's hard to trust anything about it.
This crap started around March of 2017 the local official coop station happens to be run by the radio station owner in Valentine too so everyone pretty much knows what's up with the Valentine KVTN ASOS. Just a short example without getting into full detail about being above freezing during icing events, the ASOS inability to reach full saturation so now the max humidity is 94% the AP ASOS has had 9-100+ days while all the other local Wx stations including the COOP-3 this summer and it goes on and on. Really rock-solid case they are tampering with the temperatures on these FAA weather stations likely inserting a multiplier because the hotter it gets the wider the spread from other thermometers.
I'm just saying what my experience is. Havn't had any high DP's above 71 and don't want any. I did a check with the psychro-dyne but got distracted these were current snapshots at the time where everyone was at. . I'm not seeing anything but accuracy at the current DP, if anything it came in slightly low again. I attached a snapshot of the station I also run .67 mi east of here. The dewpoint is running lower but here in town over grass it matters.
[ You are not allowed to view attachments ]
I'm just saying what my experience is. Havn't had any high DP's above 71 and don't want any. I did a check with the psychro-dyne but got distracted these were current snapshots at the time where everyone was at. . I'm not seeing anything but accuracy at the current DP, if anything it came in slightly low again. I attached a snapshot of the station I also run .67 mi east of here. The dewpoint is running lower but here in town over grass it matters.
[ You are not allowed to view attachments ]
That’s great news. Do you know how old the sensors are and how long you’ve been using them? Please let us know if you continue to get good performance. Maybe I’ll finally come around to spending another $50 trying to give the Davis 31 another chance …
They are new units only about a month in use, Ryan at Scaled Instruments may have them specially made, only because I haven't seen the 25' cable sold anywhere else. I couldn't even find them on DI own site. All my stations are custom so I can't use the short cables that are getting shorter lately. The last one I tried I couldn't reach anywhere so had to do a splice.
TBH Davis's own online listings for spare parts (which is what we're talking about with the .221 T/H sensor) is rather hit and miss and its Search isn't great either. Their Replacement Parts PDF is the definitive listing for readily available parts - not sure that Davis make this public but try a search online for PR67 Replacement Parts 2021 - someone may have uploaded it. And also try a Google search for eg Davis 7346.221 and you'll see plenty of hits.
I wondered about that. So they have a parts list they don't publish. The old website had every part they carried.
Well I have psychro-dyne now which is pretty accurate and a new SHT-31 I always purchase the SI 25 foot 31's due to my custom station setup and I'm finding the dew point is either right on or reading low 1 degree not high. I only use dew point chasing humidity around is a waste of time. Anyway, the highest I've seen in DP is 71 and the lowest is around 48 so limited where I've checked but I no longer see those crazy high heat indices of old. Yes if you heavy aspirate it moves around a couple of degrees once the ambient gets above about 84 or so but if you don't heavily aspirate with a higher-powered AC fan the spiking movement is less.
Now yes it reads higher than the ASOS but it's correct where the ASOS is actually reading low humidity and actually is a POS itself they are force-feeding this warming by cranking the rural ASOS temperature up so it's hard to trust anything about it.
This crap started around March of 2017 the local official coop station happens to be run by the radio station owner in Valentine too so everyone pretty much knows what's up with the Valentine KVTN ASOS. Just a short example without getting into full detail about being above freezing during icing events, the ASOS inability to reach full saturation so now the max humidity is 94% the AP ASOS has had 9-100+ days while all the other local Wx stations including the COOP-3 this summer and it goes on and on. Really rock-solid case they are tampering with the temperatures on these FAA weather stations likely inserting a multiplier because the hotter it gets the wider the spread from other thermometers.
Well I have psychro-dyne now which is pretty accurate and a new SHT-31 I always purchase the SI 25 foot 31's due to my custom station setup and I'm finding the dew point is either right on or reading low 1 degree not high. I only use dew point chasing humidity around is a waste of time. Anyway, the highest I've seen in DP is 71 and the lowest is around 48 so limited where I've checked but I no longer see those crazy high heat indices of old. Yes if you heavy aspirate it moves around a couple of degrees once the ambient gets above about 84 or so but if you don't heavily aspirate with a higher-powered AC fan the spiking movement is less.
Now yes it reads higher than the ASOS but it's correct where the ASOS is actually reading low humidity and actually is a POS itself they are force-feeding this warming by cranking the rural ASOS temperature up so it's hard to trust anything about it.
This crap started around March of 2017 the local official coop station happens to be run by the radio station owner in Valentine too so everyone pretty much knows what's up with the Valentine KVTN ASOS. Just a short example without getting into full detail about being above freezing during icing events, the ASOS inability to reach full saturation so now the max humidity is 94% the AP ASOS has had 9-100+ days while all the other local Wx stations including the COOP-3 this summer and it goes on and on. Really rock-solid case they are tampering with the temperatures on these FAA weather stations likely inserting a multiplier because the hotter it gets the wider the spread from other thermometers.
Totally agree with you regarding ASOS issue. The local site near me,KINT, has been reading higher temperatures than all surrounding ASOS and private stations going on 4 months now. Also their dew point is in my opinion way off, reading low. Max humidity I have seen over the past 4 months is 94%
I have contacted the NWS in Raleigh where their technicians are stationed and was told that they do a field spot check every so often and as long as it falls within 5 degrees it’s considered good. Bullshit I say!! Trust my VP2, you bet.
I like to think that combined with feedback, maybe even from this forum and the people on it, Davis took action to improve a deficiency in their product.I have no doubt. If ValentineWeather hadn't discovered this flaw in the then new 31's, who knows if anyone of us (including Davis) would have since. I feel confident that Davis heard our squeaky wheel and oiled in a fix.
Well I was curious to see if there was any change so I purchased a 31 with the short cable from Ryan and checked the performance against my Belfort psychrometer and the results were disappointing. At room temperature I got the usual 5 to 6 percent difference to the high side. Temperature was .5 to the low side. I put in a offset to the humidity of -2% and a +.5 offset for the temperature. I’d rather have the readings to be accurate in the mid range than at saturation. I give up!
Well I was curious to see if there was any change so I purchased a 31 with the short cable from Ryan and checked the performance against my Belfort psychrometer and the results were disappointing. At room temperature I got the usual 5 to 6 percent difference to the high side. Temperature was .5 to the low side. I put in a offset to the humidity of -2% and a +.5 offset for the temperature. I’d rather have the readings to be accurate in the mid range than at saturation. I give up!
I’m sorry to hear that. I’ve been hopeful. If it’s accessible, can you provide the info or take a picture of the sticker on the back side of the sensor? Davis puts a manufacture/inspection sticker on it.
Also, I’m using the fs2 filter cap.=D>
I'm also using the stock mesh filter now (didn't before) as I think it helps with the over sensitivity
Good morning guys, I'm reading the topic, and I had problems with the davis pro 2 and davis vue sensors, could you tell me if it's the same sensor in both? I just wanted to change the sensor chip without changing the whole part
Sorry my english I'm from Brazil
IMO it is still a piece of crap. I would take a SHT-15 if I could find one. Still having wet bias issues.
How is everyone’s experience with the Davis SHT-31 sensor now? Had to put a -5% offset for mine.
How is everyone’s experience with the Davis SHT-31 sensor now? Had to put a -5% offset for mine.
Still having mid range bias here. Would love to know what Davis is doing to the sensor to cause this.
On a positive note, the temperature is pretty much spot on.
After the last two days of rain, rare, heavy fog enveloped southern AZ last night. Didn't quite get to W0X0F (at least while I was awake), but very close. My SHT31 refused to get closer than 0.1F in temp/dew spread, resulting in 99% humidity for almost seven hours til 10 this morning. Not stating anything new, just wish it would pull that 100% trigger. This sensor is about two years old. Anyone getting consistent 100% out of newer ones?