Author Topic: The Reliability of the SHT-31 Humidity Sensor & What Psychrometer Should I Buy?  (Read 85157 times)

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Offline jgentry

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I talked to one of Davis’ tech folks. He forwarded my email to their design team regarding the suggestion of them switching the temp/hum sensor from the Sensirion SHT-31 to the IST HYT-221 sensor. He won’t be able to get a response from them but he did basically say that they may not switch due to compatibility issues and would have to redesign the transmitter board. But he wasn’t a 100% percent certain in which way they would go.

The Sensirion SHT-75 is the only option Davis users have if you live in an humid environment and want fairly reliable DP readings.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline ValentineWeather

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Here are the specs:
 [ You are not allowed to view attachments ]

Randy

Offline galfert

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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.
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Offline jgentry

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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.

Agreed. Hopefully they will do it very soon.  Unless there is a better option than the HYT-221, I hope they will use that sensor. Supposedly, it can handle very high humidity environments and is chemical resistant. According to IST, this sensor is good for agricultural use, which is one of Davis main targets for their stations.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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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.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline ValentineWeather

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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.

Looks about the same as SHT15 and 75. Not as good as 31 which is basic flatline through those sub-zero temperatures.
Randy

Offline WheatonRon

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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.
« Last Edit: May 21, 2019, 04:08:38 PM by WheatonRon »
Davis VP2 with SHT31 (3 complete VP2 systems—2 with a daytime fan and 1 that has a 24 hour fan); CWOP--CW5020, FW3075 and FW4350; WU--KILWHEAT17, KILWHEAT36 and KILWHEAT39; WeatherCloud.net; CoCoRaHS--IL-DP-132; and Weatherlink 2.0

Offline CW2274

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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.
Ahhh yes, but yet you proudly display owning three of them... :-P

Offline WheatonRon

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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.
Ahhh yes, but yet you proudly display owning three of them... :-P

Unfortunately, there isn’t a better system on the market at the Davis price point.
Davis VP2 with SHT31 (3 complete VP2 systems—2 with a daytime fan and 1 that has a 24 hour fan); CWOP--CW5020, FW3075 and FW4350; WU--KILWHEAT17, KILWHEAT36 and KILWHEAT39; WeatherCloud.net; CoCoRaHS--IL-DP-132; and Weatherlink 2.0

Offline galfert

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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.

With the release of the WLL the color console with WiFi solution no longer needs to come from Davis. All we need now is for someone to come up with an app that mimics a display console. A cheap tablet is all you'll need and you are all set. We'll see that soon from some 3rd party developer.

Since the WLL release, for me this I2C bus support is the last remaining advancement into having something worthy of being called a VP3. Then I can have a new ISS with I2C sensors, a WLL that is the console to receive sensor data and 3rd party software to do what you want with the data (as Meteobridge is already supporting via WLL API), and soon the tablet display app utilizing the same WLL API that Meteobridge is using and you got yourself a VP3.
« Last Edit: May 21, 2019, 04:51:02 PM by galfert »
Ecowitt GW1000 | Meteobridge on Raspberry Pi
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Windy: pws-f075acbe
Weather Underground Issue Tracking
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Offline jgentry

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Here is a interesting video that briefly talks about the IST HYT sensors
https://youtu.be/X9vW5JroqE4
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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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>

Offline jgentry

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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.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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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.

Offline jgentry

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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.

Please do! Not sure mounting will help much except to reduce wet bias.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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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.

Not sure mounting will help much except to reduce wet bias.
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.

Offline CW2274

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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.

Offline jgentry

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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?
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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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.

Offline jgentry

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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.


Gotcha  Let me know how it performs in the long run.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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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.


Gotcha  Let me know how it performs in the long run.
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.
Who knows....

Offline WheatonRon

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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....
[/quote]

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...
Davis VP2 with SHT31 (3 complete VP2 systems—2 with a daytime fan and 1 that has a 24 hour fan); CWOP--CW5020, FW3075 and FW4350; WU--KILWHEAT17, KILWHEAT36 and KILWHEAT39; WeatherCloud.net; CoCoRaHS--IL-DP-132; and Weatherlink 2.0

Offline CW2274

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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...
Quote
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.

Offline WheatonRon

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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...
Quote
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.

I truly hope you are right, but as you stated, this newbie needs a good test in higher humidities before I send Ryan my credit card!
« Last Edit: June 25, 2019, 08:39:57 PM by WheatonRon »
Davis VP2 with SHT31 (3 complete VP2 systems—2 with a daytime fan and 1 that has a 24 hour fan); CWOP--CW5020, FW3075 and FW4350; WU--KILWHEAT17, KILWHEAT36 and KILWHEAT39; WeatherCloud.net; CoCoRaHS--IL-DP-132; and Weatherlink 2.0

Offline CW2274

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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...
Quote
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.

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've sent three back to him so far, the fourth is coming. His return policy is as good as it gets.
« Last Edit: June 26, 2019, 02:28:58 AM by CW2274 »