Author Topic: The Reliability of the SHT-31 Humidity Sensor & What Psychrometer Should I Buy?  (Read 59825 times)

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Offline CW2274

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even in fog mist my station only got to 96%.
Well, I suppose you could try the "baking method" if you wanted.

Offline fkapp

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Thanks. overall am happy as has been smooth operation. dialing in is the next chapter.
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?

Offline CW2274

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Thanks. overall am happy as has been smooth operation. dialing in is the next chapter.
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?
"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.

Read back in the thread for baking procedures, I've never done it.

Offline jerryg

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Well need to update my post too, the new 31 has been doing ok but like the other 31 it maxed out at 98% so i went ahead an baked it and now it hits a solid 99%. We have had a few nights of dense fog and it has been solid and shows no signs of any wet bias at all. I decided to bake the older 31 again because it was a little slower than the new one and it now follows the new one just fine plus with a dense fog and 99% showing it bumps 100% every so often so the baking did help it some. The old 31 is still trucking along with no problems seen.

Offline fkapp

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Forgot to mention that I came across a used wireless weather monitor II that I setup for my son who is in elementary as his first weather station as a science project together.

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.

Just wanted to mention that another WM II is still going strong
« Last Edit: April 21, 2020, 02:36:20 PM by fkapp »

Offline CW2274

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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.


Offline jerryg

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Update the newest 31 is still working fine with no bias seen and works good from low humidity to the max of 99%.  =D>

Offline jgentry

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On an interesting note....There is a guy on the WeatherFlow forum that received his WeatherFlow Tempest station yesterday and the SHT31 in the Tempest has performed really well so far.  The humidity sensor reached to 100% this morning.

Here is his station webpage. https://tempestwx.com/station/18140/ and https://smartweather.weatherflow.com/station/18140/grid

Here are the surrounding NWS/RAWS stations
 https://mesowest.utah.edu/cgi-bin/droman/trend_zip_mm.cgi?zipcode=33186&type=0&radius=25&noho=1&rawsflag=1&orderby=p&mode=
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline drew1021

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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.
VP2 with 24 hour FARS. WU: KNCLEWIS2. CWOP/APRS: DW4712, COCORAHS: NC-FR-7

Offline galfert

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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.

From Sensirion's datasheet...

Reconditioning Procedure
The following reconditioning
procedure may bring the sensor back to calibration state:
Baking: 100 105C at < 5%RH for 10h
Re-Hydration: 20 30C at ~ 75%RH for 12h
Ecowitt GW1000 | Meteobridge (WeatherBridge)
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Windy: pws-f075acbe
Weather Underground Issue Tracking
Tele-Pole

Offline drew1021

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So do you wrap the sensor with foil and place it on a baking sheet
VP2 with 24 hour FARS. WU: KNCLEWIS2. CWOP/APRS: DW4712, COCORAHS: NC-FR-7

Offline jerryg

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What i use and it works real well is a cheap table top toaster oven that i set with a calibrated thermometer  to 220 degrees and it cycles between 215 to 225. It has worked real well on several sensors that i just put in the oven without any wrapping. I place it towards the front door so it doesn't get too close to the element. I have not had any type of melting problem with the temperature being that low.

Offline drew1021

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Great idea, not sure I want to buy a toaster oven just for this though.
VP2 with 24 hour FARS. WU: KNCLEWIS2. CWOP/APRS: DW4712, COCORAHS: NC-FR-7

Offline CW2274

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Great idea, not sure I want to buy a toaster oven just for this though.
Celebrate afterwards with some tater tots...

Offline Intheswamp

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Davis VP2, v3.12
Cumulus v1.9.4  Build 1079
Today's weather beats no weather at all!
www.beeweather.com
Nope, I still haven't replaced that humidity sensor...<grin>

Offline jgentry

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Ive now have some experience with two WeatherFlow Tempest weather stations. Not sure how they did it, but the SHT-31 in their station doesnt have any wet bias issues and it easily goes up to 100%. Keep in mind that this happens right out of the box and its before WF does any further calibrations to it.
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358