Author Topic: Sensirion SHT-75 is now unavailable  (Read 5636 times)

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Offline jgentry

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Sensirion SHT-75 is now unavailable
« on: February 25, 2019, 08:39:51 PM »
Looks like the Sensirion SHT-75 is finally unavailable. Will say that sensor did performed better at times than the 31 but overall, performed about the same in terms of humidity IMO. But I’ll rather have the 75 over the 31 anyday.

But if anyone can figure how to get the Davis transmitter or console to work with the HYT-221 sensor from Innovative Sensor Technology, I’ll be eternally grateful.

For those that have used the HYT-221, does it have a wet or dry bias?
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline hwcorder

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Re: Sensirion SHT-75 is now unavailable
« Reply #1 on: February 26, 2019, 09:52:42 AM »
Saw Digikey has a little over 400 left. Just bought a few more just in case.


Offline ValentineWeather

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Re: Sensirion SHT-75 is now unavailable
« Reply #2 on: February 26, 2019, 01:12:17 PM »
Last year Newark had a stick of 10 for $22 each now $29. Just purchase 10 or so and never worry about it, over 1000 in stock. By the time you need new sensors something new will be out. least I'm hoping.

 https://www.newark.com/sensirion/sht75/humidity-temperature-sensor/dp/18M2988?MER=bn_level5_5NP_EngagementRecSingleItem_1
Randy

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #3 on: February 26, 2019, 03:40:04 PM »
Just for info, i found a site that has a lot of them in stock but it is in China which means they are probably reject sensors lol. They say they are Sensirion  sensors so i ordered one just to see if they are any good, free one month shipping lol. The price is good at $21.85 if they work, so will have one here in several weeks and will compare it to good sensor and let everyone know the results.

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #4 on: February 27, 2019, 02:03:30 PM »
Got email this am that sensor has shipped, now we will see how long it takes to get here. :shock:

Offline ValentineWeather

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Re: Sensirion SHT-75 is now unavailable
« Reply #5 on: February 27, 2019, 02:21:43 PM »
 [tup] Good.
Hope there not rejects as you mentioned. Or worse Chinese knockoffs like they do with everything else.
Randy

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #6 on: February 27, 2019, 02:34:31 PM »
Yea that's the deal, but looking at the pictures the sensor has the Sensirion markings and is in the factory package, so hope everything on the up and up. I wonder if Sensirion culls the sensors by performance and prices them different? They say the sensors are from Sensirion so we shall see. The Chinese or the best knock off artist in the world so who knows.

Offline CW7491

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Re: Sensirion SHT-75 is now unavailable
« Reply #7 on: February 27, 2019, 03:22:51 PM »
I’ve finally given up on Sensirion in general. I have the good fortune of having held on to my old analog temperature/humidity sensor from the pre2006 VP2 days (the 7346.029). At 14 years old, I wasn’t sure what kind of performance I’d get from it, although for most of that time it hasn’t been exposed to the extremes of outdoor conditions. I plugged it in and it worked and the temperature matched my other sensors. I placed a wet cloth over it and it read 100% humidity within 5 mins. I installed it as my primary sensor on 23Feb. We’ve had unusually dry weather in western Washington for this time of year (humidity down near 30%) the last 2 days. It has performed well.
 
Previously I was using the SHT75, which for humidity was performing better than the Davis 31, but with the continuous wet conditions, it still suffered from a pretty bad wet bias when things would dry out. I used an offset and calibration on the SHT75 of (1.061x)-5 in Cumulus. With the analog, I am using no calibration or offset. It’s really a shame Davis could not source these humidity elements any longer. I’ll see how it does over the long term, but if you’re interested to see how it compares, the nearest NWS ASOS is KTIW. KSEA and KBFI aren’t too far (see link). Everything prior to 23Feb was the SHT75 with calibration setting. Everything after is the old analog.

https://weather.gladstonefamily.net/qchart/C7491?date=20190227&addnl=KTIW&addnl=KSEA&addnl=KBFI

05Feb really gives a good demonstration of the wet bias after a long wet period with the Sensirion:
https://weather.gladstonefamily.net/qchart/C7491?date=20190206&addnl=KTIW&addnl=KSEA&addnl=KBFI
« Last Edit: February 27, 2019, 03:33:08 PM by CW7491 »

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #8 on: February 27, 2019, 09:18:39 PM »
Well now i am confused, how did you get a analog sensor to work in a digital sensors place? I thought that would not work. Ok did some checking and it looks like the sensor switch happened around the 2006-2007 iss change over and those would do either sensor but not sure if that holds true for later iss boards.
« Last Edit: February 27, 2019, 09:26:31 PM by jerryg »

Offline jgentry

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Re: Sensirion SHT-75 is now unavailable
« Reply #9 on: February 27, 2019, 09:42:49 PM »
I’ve finally given up on Sensirion in general. I have the good fortune of having held on to my old analog temperature/humidity sensor from the pre2006 VP2 days (the 7346.029). At 14 years old, I wasn’t sure what kind of performance I’d get from it, although for most of that time it hasn’t been exposed to the extremes of outdoor conditions. I plugged it in and it worked and the temperature matched my other sensors. I placed a wet cloth over it and it read 100% humidity within 5 mins. I installed it as my primary sensor on 23Feb. We’ve had unusually dry weather in western Washington for this time of year (humidity down near 30%) the last 2 days. It has performed well.
 
Previously I was using the SHT75, which for humidity was performing better than the Davis 31, but with the continuous wet conditions, it still suffered from a pretty bad wet bias when things would dry out. I used an offset and calibration on the SHT75 of (1.061x)-5 in Cumulus. With the analog, I am using no calibration or offset. It’s really a shame Davis could not source these humidity elements any longer. I’ll see how it does over the long term, but if you’re interested to see how it compares, the nearest NWS ASOS is KTIW. KSEA and KBFI aren’t too far (see link). Everything prior to 23Feb was the SHT75 with calibration setting. Everything after is the old analog.

https://weather.gladstonefamily.net/qchart/C7491?date=20190227&addnl=KTIW&addnl=KSEA&addnl=KBFI

05Feb really gives a good demonstration of the wet bias after a long wet period with the Sensirion:
https://weather.gladstonefamily.net/qchart/C7491?date=20190206&addnl=KTIW&addnl=KSEA&addnl=KBFI

100% in agreement with you.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline ValentineWeather

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Re: Sensirion SHT-75 is now unavailable
« Reply #10 on: February 27, 2019, 10:22:19 PM »
Well now i am confused, how did you get a analog sensor to work in a digital sensors place? I thought that would not work. Ok did some checking and it looks like the sensor switch happened around the 2006-2007 iss change over and those would do either sensor but not sure if that holds true for later iss boards.

I'm wondering too.  Unless he has an old VP unit.
Randy

Offline CW2274

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Re: Sensirion SHT-75 is now unavailable
« Reply #11 on: February 27, 2019, 10:32:41 PM »
Hell, I'm so confused on what goes with what anymore, I quit asking...

Offline CW7491

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Re: Sensirion SHT-75 is now unavailable
« Reply #12 on: February 27, 2019, 11:14:34 PM »
When they switched to the digital sensor around 2006, they made the ISS capable of working with the new digital sensor as well as the old analog sensor I presume because they still had analog sensors in the supply chain. The incompatibility comes in with trying to use a digital sensor with a pre-2006 ISS. I had an old analog sensor from a pre-2006 cabled VP2. My current wireless ISS is a 2006 model that came with the SHT11 and is compatible with the old analog sensor.

I believe more recent ISSs up to the current are still compatible with the analog sensor, but I’m not certain, especially after the recent modification for the SHT31. It’s almost irrelevant though as the real trouble is finding an analog sensor as they have been out of production for years now.

« Last Edit: February 28, 2019, 07:15:42 AM by CW7491 »

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #13 on: February 28, 2019, 10:32:31 AM »
Ok now that makes sense, an older iss. I guess at sometime that backward capability was dropped, doesn't really matter anyway just didn't know you had a iss that old and still working. Have you been using that iss all these years or did you take it out of storage?

Offline hwcorder

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Re: Sensirion SHT-75 is now unavailable
« Reply #14 on: February 28, 2019, 11:28:10 AM »
Yeah I wish I would have never gotten rid of my analog sensors now. Another advantage I think they had was that you could perform field calibration using adjustment screws. I wonder if the old temp/hum modules are compatible with newer analog sensors today?

Offline CW7491

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Re: Sensirion SHT-75 is now unavailable
« Reply #15 on: February 28, 2019, 03:39:03 PM »
Ok now that makes sense, an older iss. I guess at sometime that backward capability was dropped, doesn't really matter anyway just didn't know you had a iss that old and still working. Have you been using that iss all these years or did you take it out of storage?

It’s actually been working almost all these years. There were a few years I was living in places I could not have it set up.

Yeah I wish I would have never gotten rid of my analog sensors now. Another advantage I think they had was that you could perform field calibration using adjustment screws. I wonder if the old temp/hum modules are compatible with newer analog sensors today?

The VP2 analog sensor doesn’t have those calibration screws. Those maybe were for the WMII? The humidity element is a 2 pin thin film capacitor. If you could find a manufacturer of the actual element, it could be plug and play. I’ve searched in vain to find a potential replacement if I were to need it, but it seems obsolete. I guess that’s why everyone from Davis to Rainwise have gone to Sensirion. The specs on paper are superior for the digital sensors, but the real world application seems to tell another story.

I’ve reposted pictures from elsewhere on this forum. The blue dot is the thermistor and the thin film humidity element is removable.
Looks like a cheap version of Vaisala
https://store.vaisala.com/eu/vaisala-intercap-humidity-sensor/15778HM/dp
 [ You are not allowed to view attachments ]  [ You are not allowed to view attachments ]
« Last Edit: February 28, 2019, 04:15:44 PM by CW7491 »

Offline Jstx

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Re: Sensirion SHT-75 is now unavailable
« Reply #16 on: February 28, 2019, 06:00:02 PM »
[quote author=CW7491

The VP2 analog sensor doesn’t have those calibration screws. Those maybe were for the WMII? The humidity element is a 2 pin thin film capacitor. If you could find a manufacturer of the actual element, it could be plug and play. I’ve searched in vain to find a potential replacement if I were to need it, but it seems obsolete. I guess that’s why everyone from Davis to Rainwise have gone to Sensirion. The specs on paper are superior for the digital sensors, but the real world application seems to tell another story.

I’ve reposted pictures from elsewhere on this forum. The blue dot is the thermistor and the thin film humidity element is removable.
Looks like a cheap version of Vaisala
https://store.vaisala.com/eu/vaisala-intercap-humidity-sensor/15778HM/dp
[attachment id=1 msg=372306][attachment id=2 msg=372306]
[/quote]

That "thin film humidity element" is sort of cute, reminds one of a washed sheet flapping on a clothesline (y'all remember your mom doing the laundry?). That's all I got...

Offline jgentry

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Re: Sensirion SHT-75 is now unavailable
« Reply #17 on: March 04, 2019, 12:57:43 PM »
I’ve finally given up on Sensirion in general. I have the good fortune of having held on to my old analog temperature/humidity sensor from the pre2006 VP2 days (the 7346.029). At 14 years old, I wasn’t sure what kind of performance I’d get from it, although for most of that time it hasn’t been exposed to the extremes of outdoor conditions. I plugged it in and it worked and the temperature matched my other sensors. I placed a wet cloth over it and it read 100% humidity within 5 mins. I installed it as my primary sensor on 23Feb. We’ve had unusually dry weather in western Washington for this time of year (humidity down near 30%) the last 2 days. It has performed well.
 
Previously I was using the SHT75, which for humidity was performing better than the Davis 31, but with the continuous wet conditions, it still suffered from a pretty bad wet bias when things would dry out. I used an offset and calibration on the SHT75 of (1.061x)-5 in Cumulus. With the analog, I am using no calibration or offset. It’s really a shame Davis could not source these humidity elements any longer. I’ll see how it does over the long term, but if you’re interested to see how it compares, the nearest NWS ASOS is KTIW. KSEA and KBFI aren’t too far (see link). Everything prior to 23Feb was the SHT75 with calibration setting. Everything after is the old analog.

https://weather.gladstonefamily.net/qchart/C7491?date=20190227&addnl=KTIW&addnl=KSEA&addnl=KBFI

05Feb really gives a good demonstration of the wet bias after a long wet period with the Sensirion:
https://weather.gladstonefamily.net/qchart/C7491?date=20190206&addnl=KTIW&addnl=KSEA&addnl=KBFI

You’re definitely right about the old sensor! Just looking through your data, it matches up with the airport really well. Sensirion sucks when it comes to humidity.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW7491

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Re: Sensirion SHT-75 is now unavailable
« Reply #18 on: March 04, 2019, 07:30:02 PM »
Yeah, I’m in Europe for the next week or so for work and I’m unable to spot check with my psychro dyne. It’s too bad too because the low humidity levels the last several days are really anomalous in the Seattle area this time of year. Lots of extreme local effects from proximity to water and downsloping and upsloping winds. By the time I get back, the pattern is likely to pass.

I’ve actually been concerned that it might even be reading too low at low humidity levels, but until I can compare side by side to the psychro dyne, it’s hard to say. I’m located between KTIW and KSEA. I’ve been running right between them for dewpoint. Seems reasonable for the downsloping winds and the proximity to the sound. For anyone interested, I can post the spot check results from the psychro dyne when I am back.

Offline jgentry

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Re: Sensirion SHT-75 is now unavailable
« Reply #19 on: March 05, 2019, 05:50:18 PM »
Yeah, I’m in Europe for the next week or so for work and I’m unable to spot check with my psychro dyne. It’s too bad too because the low humidity levels the last several days are really anomalous in the Seattle area this time of year. Lots of extreme local effects from proximity to water and downsloping and upsloping winds. By the time I get back, the pattern is likely to pass.

I’ve actually been concerned that it might even be reading too low at low humidity levels, but until I can compare side by side to the psychro dyne, it’s hard to say. I’m located between KTIW and KSEA. I’ve been running right between them for dewpoint. Seems reasonable for the downsloping winds and the proximity to the sound. For anyone interested, I can post the spot check results from the psychro dyne when I am back.

I’ll definitely be interested.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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Re: Sensirion SHT-75 is now unavailable
« Reply #20 on: March 11, 2019, 12:22:05 PM »
Contacted Davis about switching their temp/hum sensor from Sensirion to theHYT-221 sensor. Will let you know what they say
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jerryg

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Re: Sensirion SHT-75 is now unavailable
« Reply #21 on: March 13, 2019, 03:52:00 PM »
Ok got my new 75 sensor in from China today, so it took about 2 weeks to get here, and i have it running in test setup. It is a real Sensirion sensor in the factory packaging and shipped in a static free bag. Now i will let it run for a few days to let it adjust itself and get moistened up. First readings temp looks right on and the humidity is close but needs some time to settle in. The main thing it is a real sensor and it is alive for now lol.


Offline jgentry

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Re: Sensirion SHT-75 is now unavailable
« Reply #23 on: March 14, 2019, 06:08:07 PM »
Using my Kestrel DROP to guide me in this process, I decided to do an offset on my console for humidity by subtracting 3% and my DP is now accurate. Yes, my high humidity readings will be off but overall, my DP will be accurate.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline CW2274

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Re: Sensirion SHT-75 is now unavailable
« Reply #24 on: March 14, 2019, 06:50:40 PM »
Using my Kestrel DROP to guide me in this process, I decided to do an offset on my console for humidity by subtracting 3% and my DP is now accurate. Yes, my high humidity readings will be off but overall, my DP will be accurate.
With my 31 I use -2% and it works very well between ~3 to 90%. If I expect significant time outside those extremes, I'll take the correction out then reapply it when necessary.