Author Topic: Cold temperature SHT31 vs 75  (Read 1297 times)

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Offline ValentineWeather

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Cold temperature SHT31 vs 75
« on: November 09, 2018, 08:13:57 AM »
For anyone using the SHT75 it runs .5F warmer in single digits. I'm going to keep this test going throughout winter and report on this thread as we get below zero. The Pro shield has the SHT75.... Fars and standard the SHT31.
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Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #1 on: November 09, 2018, 08:31:11 AM »
Dropped another degree now differential is .6
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Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #2 on: November 10, 2018, 04:39:27 AM »
Here is difference at 16 coming in at +.3. The Pro shield has the SHT75.
Only doing these comparisons at night with good wind mixture so shield difference passive vs FARS don't come into play.  Both Pro and Standard Meteo shields are passive with similar design.
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Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #3 on: November 12, 2018, 07:39:46 PM »
Interesting. Keep us posted!
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #4 on: November 27, 2018, 10:15:05 PM »
How is your test still coming along?
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #5 on: November 28, 2018, 06:33:19 AM »
How is your test still coming along?

Haven't had anything colder yet. I did this test with a chest freezer before but temperature changes so fast during freezer cycle can't really trust so wanted to confirm under steadier conditions.   
Randy

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #6 on: December 08, 2018, 04:04:32 AM »
At zero 0 looks like the SHT75 runs full 1 warm. The SHT31 is in standard shield, SHT75 in the pro shield.
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Randy

Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #7 on: December 18, 2018, 10:45:45 PM »
At zero 0 looks like the SHT75 runs full 1 warm. The SHT31 is in standard shield, SHT75 in the pro shield.
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Interesting. But will say thats within specs of the 75 if my memory serves me correctly. Does your calibrated thermometer agreeing with your 31?
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #8 on: December 19, 2018, 09:33:46 AM »
At zero 0 looks like the SHT75 runs full 1 warm. The SHT31 is in standard shield, SHT75 in the pro shield.
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Interesting. But will say thats within specs of the 75 if my memory serves me correctly. Does your calibrated thermometer agreeing with your 31?

The thread isn't whether the 75 is within specs but where is it compared to the 31. We have some now running the SHT75 year round even in cold climates because of the high humidity bias displayed by the Davis version of the SHT31. From what I'm seeing the 75 specs are tighter than datasheet. Example at 0F (1 vs 1.6F) on datasheet C needs to be converted.
Yes the 31 is right with the Certified +/- .2F.
Randy

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #9 on: December 19, 2018, 09:43:40 AM »
Maybe better wording is on the tighter side of specs. Because it does say (+/-).
Randy

Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #10 on: December 21, 2018, 07:43:05 PM »
At zero 0 looks like the SHT75 runs full 1 warm. The SHT31 is in standard shield, SHT75 in the pro shield.
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Interesting. But will say thats within specs of the 75 if my memory serves me correctly. Does your calibrated thermometer agreeing with your 31?

The thread isn't whether the 75 is within specs but where is it compared to the 31. We have some now running the SHT75 year round even in cold climates because of the high humidity bias displayed by the Davis version of the SHT31. From what I'm seeing the 75 specs are tighter than datasheet. Example at 0F (1 vs 1.6F) on datasheet C needs to be converted.
Yes the 31 is right with the Certified +/- .2F.

Thanks for the info!
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #11 on: February 07, 2019, 06:56:14 AM »
Haven't updated much so here is the difference at -5F. The Pro is the SHT-75.  Good air mix this morning so no passive vs fars issues.
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Randy

Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #12 on: February 07, 2019, 12:08:59 PM »
Interesting. Not too bad if the 31 is right in the money.
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: Cold temperature SHT31 vs 75
« Reply #13 on: February 08, 2019, 04:40:38 AM »
Even better news the differential spread isn't getting bigger as temperture drops, so these 75's can be used year round as long as the user puts a little - bias (1) below zero (F).
The 75 has superior humidity when dewpoint is above 55. Jerry's along Gulf of Mexico shows SHT75 is less prone to get high humidity saturation when humidity levels stay above 90% over extended periods of several days.
Pro shield is the sht75 sensor in image.
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Randy

Offline jgentry

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Re: Cold temperature SHT31 vs 75
« Reply #14 on: February 09, 2019, 10:09:39 AM »
Even better news the differential spread isn't getting bigger as temperture drops, so these 75's can be used year round as long as the user puts a little - bias (1) below zero (F).
The 75 has superior humidity when dewpoint is above 55. Jerry's along Gulf of Mexico shows SHT75 is less prone to get high humidity saturation when humidity levels stay above 90% over extended periods of several days.
Pro shield is the sht75 sensor in image.
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Good deal! I probably wont have to worry about that because Im in Alabama. Lol. But interesting info about humidity. Ill say its overall better than the 31 but with my experience, the 75 has shown some wet bias at times. In example: Here are the currents in my area.

Davis: 40/27
Nearby ASOS 39/23
Kestrel 40/26

Will note that the ASOS DP just dropped to 23. It was sitting at 25 along with the Kestrel not long ago.
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

 

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