Author Topic: build your own temp/hum sensor for vp2  (Read 37314 times)

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Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #25 on: January 13, 2012, 06:10:09 PM »
No i just did a general comparison, nothing complex, as to how they read compared to each other. I have them all uploading to wu and could watch them as they changed and i looked at the  info on wu to see how they did over a long period of time. Just something to do to pass the time being retired i have time to do this kind of thing lol.

Offline DanS

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Re: build your own temp/hum sensor for vp2
« Reply #26 on: January 13, 2012, 06:21:52 PM »
No i just did a general comparison, nothing complex, as to how they read compared to each other. I have them all uploading to wu and could watch them as they changed and i looked at the  info on wu to see how they did over a long period of time. Just something to do to pass the time being retired i have time to do this kind of thing lol.

Another visual way to compare between stations is have the stations you want to compare with all upload to CWOP. Then, pick the station you want to use as the reference and open it's page on CWOP. Click on 'findu' , 'Quality Control Graphs for (station name)'. At the bottom click to select the other stations you want to compare to then 'Add to Charts'. You will get an overlay of all the temps, humidity, Dew pt., pressures, wind. I use this to keep an eye on things daily.

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #27 on: January 13, 2012, 06:33:48 PM »
Yes that would work pretty well. I was just curious how the better speced sensor was compared to the one davis uses. I do not know why all the ones i have top out at 98, i guess at that humidity it is wet lol. I could just check the show 100 box in wd. For the most part the sensors are just fine, well within specs. I just needed to satisfy my curiosity. I am going to leave the homemade sensor on my main site because i like how it seems to follow the metars closely. I ordered the 75 sensor that is already mounted on a board with the capacitor on board and the filter housing that goes on the sensor, i might have to make it fit the 75 board but will try it anyway. The cover will help keep dust and stuff out of the sensor. It will be another little fun project.

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #28 on: January 17, 2012, 08:39:40 PM »
Got the sht75 in today plus i ordered the sf-1 filter which is a plastic housing with a filter screen that fits over the sensor to keep dust, bugs and water drops out. The 75 is alot easier to work with if you are building a spare sensor rather than replacing one on the Davis board. The sensor will not fit neatly into the filter which is made for a larger square board so i cut a notch in the bottom of the filter so the 75 fit neatly in the housing and sealed it. Then i soldered the cable leads to the pins carefully bending one up and one down etc. so they would not touch. Then i put the sensor in an old temp/hum housing i had from an old station. I have it running now and looks real good comparing to the other sensors. I like the filter, makes it easy to mount and seal the sensor plus keeps all the gunk out. Now i will let it age for awhile and compare the readings with the other sensors to see how it ages if at all. It only took me about a half hour to assemble the sensor, the only thing will be how long will it last outside without all the potting that Davis does. I had some of the os sensors outside for years without any corrosion problems and they were not sealed so hope that is a good omen.

Offline AVman

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Re: build your own temp/hum sensor for vp2
« Reply #29 on: February 05, 2012, 12:40:46 AM »
Would this work on a VP1?

Thanks!
  
Edit 2/5/2012
I think I answered my own question



This is the Vantage Pro 1 temp / humidity sensor (the the protective cover taken off), and it is defiantly not an SHT11

Any idea on what it actually is? If I could find that white sensor (marked Y421 on the plastic) I could easily swap it out when it dies. I have 5 of these things around Gloucester, MA (a lot of salt and wind) and it would be nice to fix it myself when they die.

Edit Later 2/5/12
Found out the white thing is the humidity sensor, and the blue thing is the temp sensor.  I pulled the white thing and the humidity read 100%, which also means if someone has a station reading 100% it could simply be a bad connection to the humidity sensor.
« Last Edit: February 05, 2012, 03:10:33 PM by AVman »

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #30 on: February 23, 2012, 12:01:57 PM »
Well its time for an update on my experiments with the 15 sensor. In my stevenson screen i have mounted side by side three sensors, one is a 15 i built and put in an old sensor housing with no dust screen, the second is a sparkfun breakout board with the 15 on it and the sf1 dust filter, the third is a 15 mounted on a davis sensor board that went bad. I have been doing some comparisons since we have been having alot of dense fog lately and all three sensors show 100 percent when dense fog is happening. The thing i noticed most is the sensor with the davis screen on it had a pretty long lag time before the humidity started to drop and rise when the other two where tracking each other pretty close. This am it was foggy again and the two sensors that track showed 90% while the Davis showed 94% so i removed the screen from the Davis and by the time i got into the house it was showing 90% also and has been tracking with the other two just fine. So it seems to me the dust cover causes a pretty good lag time on the Davis sensor, it does catch up with the other two when the humidity stabilizes some. The temps are real good and track withing a couple of tenths of each other. I have a regular davis sensor in a daytime fars housing that i modified to run on ac so i could run it at night and with the fan running it did not have the lag time that the non fars davis sensor has. It looks to me like the Davis sensor is better at tracking the temp/hum with the fan pulling air over it all the time. The lag time when the fog is dense is because we get dense fog when the wind is not blowing are is very low mph and the sensor is not getting the air movement it needs. We are due a cold front in tonight and the humidity is supposed to get down low and i can compare them on the low side for a change lol.  \:D/

Offline dalecoy

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Re: build your own temp/hum sensor for vp2
« Reply #31 on: February 23, 2012, 01:16:10 PM »
From that single report (and of course with common sense, regardless of that report), a FARS tends to improve average accuracy and decrease response time of sensors.

...translation: a FARS is really necessary if you want accurate realtime data. Agree?

Exactly what do you mean by "accurate data"?

Exactly what do you mean by "realtime data"?

Offline d_l

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Re: build your own temp/hum sensor for vp2
« Reply #32 on: February 23, 2012, 08:21:46 PM »
...translation: a FARS is really necessary if you want accurate realtime data. Agree?

If your weather site has continuous winds faster than about 2-3 mph, then the FARS probably isn't necessary for the various Davis non-FARS radiation shields.  I've come to this conclusion after checking various Davis spec sheets and personal experience with Davis units.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline Yfory

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Re: build your own temp/hum sensor for vp2
« Reply #33 on: February 23, 2012, 08:50:23 PM »
I have not said much here, but I follow these discussions daily.

I have multiple stations, an old Davis Vantage, a new Vantage View, and a precision sensor system I am building myself as a calibration unit.

I have experimented with and without fan aspiration for months and I am a STRONG advocate of sensor aspiration. Each sensor, assuming all to be fairly well calibrated, has its own response time to show air readings so it is simply a matter exposing the sensor the real air temperature as quickly as possible without exposing the sensors to sunlight or rain.

To the extent of a sensor's isolation from sunlight and rain, it's readings are delayed. The delay depends on how long it takes the outside air to get to the sensor. I have seen as much as 20 minutes difference in a daily high temperature reading from two good sensors, depending on the shielding, aspiration, and and/or wind.

Good isolation from direct sun and rain is important for accurate temperature and humidity measurements but blowing outside air over the sensor, with a fan, is even better.

I am now experimenting with a simple 2 inch 12 VDC, 1.5 watt computer fan mounted on edge inside my old Davis Vantage Pro and it works very well and gives a nearly simultaneous reading compared to a fast calibration thermometer outside the Davis unit (but in the shade).

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #34 on: March 01, 2012, 03:32:01 PM »
I liked the results of a fars unit so i broke down and ordered the parts to convert my Davis over to a 24 hr fars. I got all the parts from Archer Trading Post. I got the 24 hr solar panel, two 2300 mah batteries the covers and o rings plugs Archer now has the battery clips with wires that fit into the empty battery housings on the daytime fars. I got the power control board also. The control board is not very complex, it charges the batteries through a blocking diode and a 50 ohm current limiting resistor. The fan has three leads, the black is battery neg. The center red lead goes thru a 10 ohm resistor to battery plus and the outside red lead goes directly to the solar panel plus. With the batteries being in parallel it gives you alot of run time. The hardest part was mounting the panel to the top of the screen, the screws that come with the daytime fars are too long so had to cut off about three quarter inch. The rain gauge base has its own 3 holes to mount spacers in to set the assembly back aways so as not to shield the fan solar panel. I found some spacers in my goodie box that worked and i have it online now to do some comparisons with my other sensor housings. I think Davis ought to sell a kit for this mod instead of pieces.

Offline d_l

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Re: build your own temp/hum sensor for vp2
« Reply #35 on: March 01, 2012, 04:47:07 PM »
I think Davis ought to sell a kit for this mod instead of pieces.

Jerry, I think they did once.  The 7755 Solar-Powered Fan-Asperated Radiation Shield looks to be nearly identical to the 24-Hr FARS although I haven't compared the measurements.  It does have the inner wind tunnel tube (sensor chamber) that is shielded from radiation and directs air flow across the sensors which a converted daytime FARS doesn't have.

http://www.davisnet.com/product_documents/weather/manuals/07395-084_IM_07750_7755.pdf
http://www.davisnet.com/product_documents/weather/spec_sheets/7755_spec.pdf

Differences that I've noted from the current 24-hr FARS are the sensors, possibly the hardware and the arrangement of it that attaches to the rain collector base, and the lack of a wiring-pass-through hole in the solar panel.

It may be that an old 7755 if still for sale someplace on the internet, might be a better 24-hr FARS than a conversion job.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #36 on: March 01, 2012, 05:53:26 PM »
I saw that and could not find any for sell i used the manual to help see how the wiring was set up. So i guess making do is the only way to get there if you did not buy the 24 hr to start with. I am set up now to compare it with my stevenson screen and the daytime fars as well as the nonfars shield. Should be interesting to see how it all shakes out.

Offline d_l

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Re: build your own temp/hum sensor for vp2
« Reply #37 on: March 04, 2012, 12:28:51 PM »
Here is one still "offered" for sale: http://www.wxbureau.com/files/7755.html; however, I think that may be a ghost website that is residing on a web server well past its expiration date. 

It looks like it died circa 2004.  It would be neat if they they are still in operation and still had 7755s in stock.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline DaleReid

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Re: build your own temp/hum sensor for vp2
« Reply #38 on: March 04, 2012, 05:23:36 PM »
How do you know when the original factory supplied sensor is beginning to fail?

Is there a loss of linearity? Failure to reach max of 100%, or a narrowed range?

Can the humidity function fail or be imprecise and the temp still ok and track other thermometers?

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Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #39 on: March 04, 2012, 07:28:16 PM »
I am far from an expert on this stuff but i can tell you from experience that mine was reading ok and then the next time i looked it had dropped 50% below what it was but the temperature was correct. The readings were all over the place but the temp always read right. I think the humidity can go bad with the temp being ok but if the temp goes bad it will cause the humidity to read wrong. Maybe someone else can explain it better.

Offline DaleReid

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Re: build your own temp/hum sensor for vp2
« Reply #40 on: March 04, 2012, 08:40:49 PM »
Thanks Jerry,
I have just brought my Davis Pro back on line after being quiet since last summer, and watching it compared to my other stations that track pretty close to one another and drat, I see that my humidity is 50% on the Davis while the others are 78 to 81%....

Grrr, maybe I'll be reading this thread a lot closer than I was to see what my options to get back to being more accurate.

I appreciate all the enthusiasm the contributors have here.

Dale
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Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #41 on: March 15, 2012, 10:44:46 PM »
I finally got some info on the 24 hr shield and was surprised that it has a number that is 6153s, s is for shield i would think, it is a replacement for the 6153 shield and does not include the sensor. I was looking on Archer Trading Post site and there was one showing as new for March and he had one in stock so i jumped on it and it is comming ups. I did not think you could get a shield by itself. I searched the part on Google and can not find it. Maybe with the interest people have shown in upgrading to the 24 hr fars they are going to put them out there for retrofit. From the picture it looks like all you have to do is mount the rain base on top. Might need some screws that are shorter, will find out and post here when got it up and running.

Offline moehoward4

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Re: build your own temp/hum sensor for vp2
« Reply #42 on: March 16, 2012, 05:26:54 AM »
jerryg   The guy that owns ATP is an electrical engineer, I think he is putting those fan shields together himself for sale. Saw the need and has the parts....make the sale....VERY GOOD idea for those that didn't and now want one. I don't think the price is too bad either.
« Last Edit: March 16, 2012, 05:28:31 AM by moehoward4 »
3 Davis set-ups...which one ya wanna talk about? And I got ALL my manuals....

Offline d_l

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Re: build your own temp/hum sensor for vp2
« Reply #43 on: March 16, 2012, 11:11:35 AM »
Frankly that is a very good price on that 24-hr FARS conversion kit!  A daytime only kit is ~$100.

jerryg, ATP is now showing zero units in stock though.  I wonder if you got the only one they had and how long it will take to restock?

Also I wonder if ATP is making these parts available by disassembling complete units and then selling the component parts?
« Last Edit: March 16, 2012, 11:19:51 AM by d_l »
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #44 on: March 16, 2012, 11:20:36 AM »
I know i saw there was only one in stock and after my order i could not find any info showing. It is due here next Tuesday and as far as how it came to be it was listed with a Davis part number so will just wait and see. The daytime fars i converted to 24 hr has been working pretty good and am looking forward to comparing the two.

Offline moehoward4

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Re: build your own temp/hum sensor for vp2
« Reply #45 on: March 16, 2012, 12:07:24 PM »
d_l    Check out the site, www.archertradingpost.com/atp, he has the parts in stock to make these so I don't think he's taking good packages apart.















3 Davis set-ups...which one ya wanna talk about? And I got ALL my manuals....

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #46 on: March 16, 2012, 12:38:26 PM »
I would not think he is making them from parts because the 24 hr assembly is different than the daytime fars conversion parts. The sensor chamber on the 24hr goes down the center of 7 of the plates with the holes in them and is open at the bottom with a screen on it. I have never seen parts for this anywhere.

Offline d_l

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Re: build your own temp/hum sensor for vp2
« Reply #47 on: March 16, 2012, 01:27:13 PM »
Disassembling a complete unit and selling it as parts could be price advantageous to a merchant if he can get all the parts sold.  Everyone knows that it costs far more to buy the individual parts and build an ISS than buying a complete unit.

Disassembling complete units would be especially profitable if there was some component that is desired by many customers and not available any where else.  A retro fit 24-hr FARS fits that description.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline jerryg

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Re: build your own temp/hum sensor for vp2
« Reply #48 on: March 16, 2012, 03:16:20 PM »
Just got of the phone with ryan and that is what he did. He parted out all the stuff and sold the shield. He said he will have one for sale from time to time when he has the parts sold, can not break up the whole iss without losing his shirt lol. So i guess it will be luck of the draw if you want one or maybe call or email him and get on a list if he has one. I do not see why Davis does not sell the shield to retrofit the standard to 24 hr. Either they buy the iss as a complete unit and do not have the shield set up separate or they do not want the general public messing around with the change out and getting poor results and then bad mouthing the product because they did something wrong. I know there are alot of technical people on here and would have no problem retrofitting one but then again there are alot of people who could break an anvil too lol.  :lol:  :lol:  :lol:

Offline moehoward4

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Re: build your own temp/hum sensor for vp2
« Reply #49 on: March 16, 2012, 03:35:22 PM »
OK OK, I stand corrected, can't be right all/any of the time. I just figured that with the parts he stocks and his knowledge that it was 'his' configuration.
3 Davis set-ups...which one ya wanna talk about? And I got ALL my manuals....

 

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