Author Topic: SHT31  (Read 2480 times)

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Offline JudinNorman

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Re: SHT31
« Reply #25 on: June 04, 2017, 10:54:39 PM »
Yes the -0.9 F offset is in the console.

And just for further clarification, you stated in another thread that you did put in the minus 0.9F offset, right?

Offline JudinNorman

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Re: SHT31
« Reply #26 on: June 04, 2017, 11:04:13 PM »
That could be the case but I have no idea or way to check,  all that I have is the data which has been consistant over the years compared to nearby stations,  I have not noticed my average temperatures getting colder or warmer compared to nearby.
Jud

If the Davis had an older SHT11 remember they aren't as accurate and very likely was off, especially if several years old they can drift.
If comparing to a nearby professional station remember they most likely have ideal setup so wouldn't surprise me if you weren't reading higher in your back yard.
I would bet the SHT31 is accurate, and the older sensor has the problem.

Offline CW2274

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Re: SHT31
« Reply #27 on: June 04, 2017, 11:13:57 PM »
Davis Temperature station sensor is the sensor that is part of the Davis Temperature Station, just measures temperature,  no humidity.
Not sure which is right,  just disappointing after 10 years of data the new data will not be close.  It screws up the freeze data,  old sensor read 32.0 which would go down as a freeze but the new sensor would read 32.8 for example and would be considered a freeze.  My first and last freeze days will be off.
Jud
Sooo, you're saying that you're unhappy that your 31 is almost for surely more accurate than either of your other sensors? When I put my 31 in I was elated at it's performance, and still am, and so is everyone else I know of. I think I'd give it shot.
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Offline JudinNorman

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Re: SHT31
« Reply #28 on: June 04, 2017, 11:38:09 PM »
I'm unhappy there is such a difference between old and new sensor.  Not sure if I can maintain my same database or should start a new one.

Davis Temperature station sensor is the sensor that is part of the Davis Temperature Station, just measures temperature,  no humidity.
Not sure which is right,  just disappointing after 10 years of data the new data will not be close.  It screws up the freeze data,  old sensor read 32.0 which would go down as a freeze but the new sensor would read 32.8 for example and would be considered a freeze.  My first and last freeze days will be off.
Jud
Sooo, you're saying that you're unhappy that your 31 is almost for surely more accurate than either of your other sensors? When I put my 31 in I was elated at it's performance, and still am, and so is everyone else I know of. I think I'd give it shot.

Offline alexstaar

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Re: SHT31
« Reply #29 on: June 05, 2017, 12:06:37 AM »
The NWS and other official climatological databases do not start new databases just because they upgrade their observing equipment. They would never have any past data to compare current data to! Don't be upset that the older sensor wasn't quite up to par with the newer one. You're dealing with a matter of a few tenths of a degree, not several whole degrees off so it's not that big of a difference in the grand scheme of things, especially over a ten year period.
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Online ValentineWeather

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Re: SHT31
« Reply #30 on: June 05, 2017, 07:53:32 AM »
As far as worrying about freezing temperatures the stainless with the temperature station is just as accurate as the SHT31 so they should come together nicely.

Where it starts losing accuracy, as temperatures rise at  82 its already +/- (1) and at 110F its bad at +/- (2).

Just be glad you upgraded to the SHT31 and enjoy.  8-)
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Offline WxLover16

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Re: SHT31
« Reply #31 on: June 11, 2017, 09:40:14 PM »
I'm unhappy there is such a difference between old and new sensor.  Not sure if I can maintain my same database or should start a new one.

Davis Temperature station sensor is the sensor that is part of the Davis Temperature Station, just measures temperature,  no humidity.
Not sure which is right,  just disappointing after 10 years of data the new data will not be close.  It screws up the freeze data,  old sensor read 32.0 which would go down as a freeze but the new sensor would read 32.8 for example and would be considered a freeze.  My first and last freeze days will be off.
Jud
Sooo, you're saying that you're unhappy that your 31 is almost for surely more accurate than either of your other sensors? When I put my 31 in I was elated at it's performance, and still am, and so is everyone else I know of. I think I'd give it shot.

Sure it sucks that there's such a drastic difference between old and new and that your old has drifted over the years, but take solace in the fact that you upgraded to the very newest in temp/humidity technology. More accurate, tighter specs, what more can you ask for?  ;)
Davis Wireless VP2 SHT31 24hr 24CFM FARS

Offline JudinNorman

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Re: SHT31
« Reply #32 on: June 11, 2017, 10:01:10 PM »
Over a week with the SHT31 installed.  The average temperature is 0.2 F higher than the Temperature Station,  the old Temp/Hum sensor averaged 0.3 F colder than the Temperature Station for years.  I would assume all these sensors are within their specs for accuracy. 
I may set up a wooden shelter with NWS thermometers.  I visited a volunteer observer 48 miles from here who has been been using the same glass thermometers for 32 years which are still working like day one.

Offline CW2274

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Re: SHT31
« Reply #33 on: June 11, 2017, 10:17:10 PM »
I visited a volunteer observer 48 miles from here who has been been using the same glass thermometers for 32 years which are still working like day one.
And will til it breaks.
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Offline Phil23

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Re: SHT31
« Reply #34 on: August 10, 2017, 06:18:10 AM »
For transmitter firmware anything built Jan 2016 or later I've found through orders with Scaled Instruments had the latest SHT31 firmware. The code doesn't have to be AS or later despite what Davis says as long as it was manufactured in Jan 2016. You can open transmitter and look at first 4 numbers after the 2 letters.

Example code of AP160101201 (Jan 2016)

Now I'm really confused.

My ISS is AR160914029.
The ISS board has Assy# 07315.115 Rev E3.

The Current Temp Sensor as a white sticker with Part# 7346.176J.

Don't seem to get many reference when I search for any of those codes.

It's an Aussie unit from our official distributor, & was on backorder waiting, for fresh stock when I ordered it back in August 2016.

Should have popped the screen off the above temp sensor when I had the Shield apart converting it to DFARS, as I find no official information as to exactly what the 7346.176C sensor is.

Real question though, is do I need to apply the offset when my SHT31 arrives.

Thanks

Phil.

Edit:

How do you determine the firmware revision of the ISS (as opposed to the console).
« Last Edit: August 10, 2017, 06:20:25 AM by Phil23 »

Offline Phil23

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Re: SHT31
« Reply #35 on: August 10, 2017, 06:21:48 AM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.

Phil.

Online ValentineWeather

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Re: SHT31
« Reply #36 on: August 10, 2017, 11:51:18 AM »
Easiest way when new SHT31 comes pop dust shield and compare to old sensor. The new sht31's are very small don't sit as high as the SHT11 and 15's. 
« Last Edit: August 10, 2017, 01:17:23 PM by ValentineWeather »
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Offline WxLover16

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Re: SHT31
« Reply #37 on: August 10, 2017, 12:38:36 PM »
Easiest way when new SHT31 comes pop dust shield and compare to old sensor. The new sht31's are very small don't set as high as the SHT11 and 15's.

Basically you'll know if you have a 31 if you can't read the 31 AT ALL. Even under a microscope the damn thing is still hard to read.
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Online ValentineWeather

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Re: SHT31
« Reply #38 on: August 10, 2017, 01:04:03 PM »
Here is 15 and new 31.  No mistaken once filter cap is removed.
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Offline johnd

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Re: SHT31
« Reply #39 on: August 10, 2017, 01:10:34 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.

Almost certainly not I would have thought, since any heating element must consume power but which is in very short supply in a wireless VP2 ISS.

But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
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Offline CW2274

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Re: SHT31
« Reply #40 on: August 10, 2017, 03:35:59 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.
But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
Yeah, there's probably a few of us trying to figure out this one.... :???:
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Offline Phil23

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Re: SHT31
« Reply #41 on: August 10, 2017, 04:33:59 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.
But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
Yeah, there's probably a few of us trying to figure out this one.... :???:

Although the whole device is tiny, (2.5 x 2.5mm), maybe the heater is very localised to the humidity sensing element & isolated from the temp sensor part or the device.

Also the data sheet states the heaters power at 4.5 to 33mW, and being that it's a completely digital device, any heating input influencing the temp element could be calculated & adjusted for within the device. The data sheet says it's for "plausibility testing only".

But I've read other stuff discussing it's relevance to improved humidity readings in high humidity circumstances when condensation is present.

Dunno, but in loose terms you could say turn the heater on for a bit, ignore the temp for a bit & focus on the humidity; turn it off; go back to reading the temp again.

Also plausible is a device (as in board) with two STH31's present. One with the heater on the other heater off.

Bit Academic, but interesting anyway.

Phil

Offline CW2274

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Re: SHT31
« Reply #42 on: August 10, 2017, 04:55:43 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.
But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
Yeah, there's probably a few of us trying to figure out this one.... :???:
Also the data sheet states the heaters power at 4.5 to 33mW, and being that it's a completely digital device, any heating input influencing the temp element could be calculated & adjusted for within the device. The data sheet says it's for "plausibility testing only".
Could you please post this "data sheet?" Don't know about anyone else, but I have no idea what you're refering to.
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Offline SLOweather

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Re: SHT31
« Reply #43 on: August 10, 2017, 05:09:47 PM »
As I recall from the SHT11 and/or SHT15 datasheets, the on-sensor heater is used to recondition the sensor after exposure to solvents during assembly/soldering. But I could be wrong...

Offline CW2274

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Re: SHT31
« Reply #44 on: August 10, 2017, 05:45:03 PM »
Okay, found this, but I have no idea what "plausibility checking" is.
4.10
Heater
The SHT3xis equipped with an internal heater, which is meant for plausibility checking only. The temperature increase achieved by the heater depends on various parameters and lies in the range of a few degrees centigrade. It can be switched on and off by command, see table below. The status is listed in the status register. After a reset the heater is disabled (default condition)
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Offline Phil23

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Re: SHT31
« Reply #45 on: August 10, 2017, 07:22:54 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.
But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
Yeah, there's probably a few of us trying to figure out this one.... :???:
Also the data sheet states the heaters power at 4.5 to 33mW, and being that it's a completely digital device, any heating input influencing the temp element could be calculated & adjusted for within the device. The data sheet says it's for "plausibility testing only".
Could you please post this "data sheet?" Don't know about anyone else, but I have no idea what you're refering to.

This is the official data sheet for the device.

https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Datasheet_digital.pdf

Few searches make mention the heater in relation to humidity & condensation.

Phil.

Offline CW2274

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Re: SHT31
« Reply #46 on: August 10, 2017, 07:41:47 PM »
Would also be curious to know if Davis is using the Heater in the SHT31 in later firmware revisions to improve temperature accuracy.
But since you've mentioned it, I do find myself curious as to how heating a temperature sensor can enhance its accuracy?
Yeah, there's probably a few of us trying to figure out this one.... :???:
Also the data sheet states the heaters power at 4.5 to 33mW, and being that it's a completely digital device, any heating input influencing the temp element could be calculated & adjusted for within the device. The data sheet says it's for "plausibility testing only".
Could you please post this "data sheet?" Don't know about anyone else, but I have no idea what you're refering to.

This is the official data sheet for the device.

https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Datasheet_digital.pdf

Few searches make mention the heater in relation to humidity & condensation.

Phil.
Yes, that's where I got my quote from two post ago.
I guess the point is you're reading into this as a potential benefit, as far as I can tell this is nothing more than a diagnostic tool.
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Offline Phil23

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Re: SHT31
« Reply #47 on: September 22, 2017, 08:19:57 PM »
Might Try & actually install this today.

Just in regards to the off-set, do I need to Increase or Decrease the reading at the console by the 0.5C off-set.

Thanks

Phil.

Offline WxLover16

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Re: SHT31
« Reply #48 on: September 22, 2017, 10:52:46 PM »
Might Try & actually install this today.

Just in regards to the off-set, do I need to Increase or Decrease the reading at the console by the 0.5C off-set.

Thanks

Phil.

If I'm not mistaken, you need to decrease the reading.
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