Topic: Reasonably Accurate Hygrometer

[kilogulf59]

I'd like to purchase a reasonably accurate (indoor) hygrometer that actually performs within it's claimed tolerance. I've purchased several that claim +/-2%, which is fine for me, tested them using various adaptations of the salt method for a high-end 75% check and a Boveda One-Step Hygrometer Calibration Kit - 32% RH for a low end and by direct comparison with each other and they are all over the map. They are not accurate nor are they even consistent.

So, how much do I have to spend to get a hygrometer, analog or digital, that is relatively accurate and consistent and which brand would you suggest?

[Old Tele man]

Sensirion™ makes & sells a stand-alone "development kit" module 'SMART GADGET' for their SHT31 chips. Try contacting them to see about getting one:
https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Smart-Gadget_User-Guide.pdf

One of our forum members here has a couple of them that he is comparison testing. The SHT31 is the same sensor chip that's used in current Davis VP2 weather stations.

[kilogulf59]

I didn't see anything regarding operational tolerance and/or accuracy or price...

[ValentineWeather]

I didn't see anything regarding operational tolerance and/or accuracy or price...

https://www.digikey.com/products/en?keywords=smart%20gadget

[kilogulf59]

Anyone ever tested them?

[ValentineWeather]

If you have a Davis VP2 made in 2016 or later the SHT31 is the Temp/hum sensor you get. Prior to 2016 many have added the SHT31.

The smart Gadget is standalone sensor with LED readout also works with phones but not necessary. You can have several of these at $28. The one I ordered was $70 when first released so price has really dropped and they still have 400+ in stock.

[kilogulf59]

Thanks for the advice folks.

No Davis here. I had an AcuRite but gave up on it.

$28 seems reasonable if they work. I am so fed up of things not working according to their specs or not at all, regardless of cost. I'm turning into the consumer from hell and if others did the same most of the junk would be off the markets. And I hate hearing 'well what do you expect for the price?". I expect it to work as advertised, simple as that, and sorry for the tirade.

[Old Tele man]

Thanks for the advice folks.

No Davis here. I had an AcuRite but gave up on it.

$28 seems reasonable if they work. I am so fed up of things not working according to their specs or not at all, regardless of cost. I'm turning into the consumer from hell and if others did the same most of the junk would be off the markets. And I hate hearing 'well what do you expect for the price?". I expect it to work as advertised, simple as that, and sorry for the tirade.

I heard an answer to your "Cannot operate a weather rock"...which goes: "...turn it over to do a 'manual reset'." (wink,wink)

[kilogulf59]

See, now why didn't I think of that 

[DaleReid]

I just ordered the evaluation kit from DigiKey, who is figuratively just up the road from me.

I've gotten some good stuff in eval kits, for less than parts sometimes.  I guess they put this together to have designers try things out and maybe build a million of something.

The interesting thing about this particular setup is that it uses low energy bluetooth to communicate too, so I could stick it in one of my many radiation shields and read the temp and humidity through a glass window with my cellular phone.  That alone is worth the $30 to fiddle with.  I see this same company has a pressure chip demo kit, too, and wonder how it would work out as a barometer?

[kilogulf59]

My sole interest is accuracy and consistency. Remember, I have trouble working my weather rock...

I noticed, while looking for the tolerance specs, that there's two series; SHT3x-DIS Series Datasheet and SHT3x-ARP Series Datasheet, which one is being sold? The DIS is slightly more accurate.

Also, has anyone here actually tested on of these for accuracy and consistency?

[ValentineWeather]

The interesting thing about this particular setup is that it uses low energy bluetooth to communicate too, so I could stick it in one of my many radiation shields and read the temp and humidity through a glass window with my cellular phone.  That alone is worth the $30 to fiddle with.  I see this same company has a pressure chip demo kit, too, and wonder how it would work out as a barometer?

FYI the bluetooth range is also low about 15' or so.

[DaleReid]

I have a Vaisala humidity calibrator that uses the three salts to give great accuracy, but I dont think I can stuff this thing, even if it is an inch across, into the holes.  So I'm not sure what I can test it against for humidity accuracy.

Yeah, the range won't be like the Rainwise LR or anything, but good enough to get to a picture window where I can go up to check on the temps while the wind is howling this winter.  I'd guess that the battery wouldn't last til spring, though.

[user3162]

Sensirion™ makes & sells a stand-alone "development kit" module 'SMART GADGET' for their SHT31 chips. Try contacting them to see about getting one:
https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Smart-Gadget_User-Guide.pdf

One of our forum members here has a couple of them that he is comparison testing. The SHT31 is the same sensor chip that's used in current Davis VP2 weather stations.

 I have a wineador for cigars. I bought three different hygrometers to monitor the humidity. One could not be calibrated, it was "Good out of the box"... not.
One could only be adjusted by 6%. I did the salt test, left it in a sealed freezer bag, at room temperature, with a salt / water solution for 12 hours, found it wasn't within 6%.
The third could be adjusted for any amount. I did the salt test and calibrated it. After a week, my humidity level did not drop below 70%. I was suspicious, so I ordered the one quoted above, to compare with what I had in the wineador. Since this one is the same sensor I put in my VP2, I have high hopes.
 I selected US Mail, but they shipped it Priority Mail, and I received it today. I will do the salt test later, see what I come up with. For now, I'll monitor it, see what I get.
Since it has blue-tooth, I installed the app for IOS. The app would be great, if the sensor is accurate. If not, It isn't the first bad hygrometer that I bought.

[ValentineWeather]

Spec sheet is available for the SHT31. With the electronics board these aren't designed to be submitted to chemicals or even outside conditions.

Smart Gadget operating temperature range: -10 to 60 °C
 The Smart Gadget is intended for indoor use only

[kilogulf59]

user3162, my results were similar though with different hygrometers. No where near their claim...and that's why I started this thread.

I did several salt tests for 24-hours, monitoring as best I could, and the units were low by 3 to 10 percentage points. Then I tested them using a Boveda 32% Low-RH One-Step Hygrometer Calibration Kit. They were from 4 to 12 percentage points high. Then I changed batteries and got similar results but from different units. Even if they could be calibrated, how the heck would I? None of them were within their own specs and none were consistent. I received refunds from Amazon and posted my results on these 4 to 5 star rated units. The manufacturers contacted me trying to play the CYA game, one claiming it was my batteries, another questioning my procedures, et cetera. All offering refund/replacement. No thanks. I, at least, got my refund and I didn't want more garbage.

Spec sheet is available for the SHT31. With the electronics board these aren't designed to be submitted to chemicals or even outside conditions.

Smart Gadget operating temperature range: -10 to 60 °C
 The Smart Gadget is intended for indoor use only

So, essentially, I have to take their word for it or test it via a side by side comparison, with a good hygrometer, which I don't have and can't seem to find? OK, back to the thread starter...

I'd like to purchase a reasonably accurate (indoor) hygrometer that actually performs within it's claimed tolerance. I've purchased several that claim +/-2%, which is fine for me, tested them using various adaptations of the salt method for a high-end 75% check and a Boveda One-Step Hygrometer Calibration Kit - 32% RH for a low end and by direct comparison with each other and they are all over the map. They are not accurate nor are they even consistent.

So, how much do I have to spend to get a hygrometer, analog or digital, that is relatively accurate and consistent and which brand would you suggest?

[ValentineWeather]

user3162, my results were similar though with different hygrometers. No where near their claim...and that's why I started this thread.

I did several salt tests for 24-hours, monitoring as best I could, and the units were low by 3 to 10 percentage points. Then I tested them using a Boveda 32% Low-RH One-Step Hygrometer Calibration Kit. They were from 4 to 12 percentage points high. Then I changed batteries and got similar results but from different units. Even if they could be calibrated, how the heck would I? None of them were within their own specs and none were consistent. I received refunds from Amazon and posted my results on these 4 to 5 star rated units. The manufacturers contacted me trying to play the CYA game, one claiming it was my batteries, another questioning my procedures, et cetera. All offering refund/replacement. No thanks. I, at least, got my refund and I didn't want more garbage.

Spec sheet is available for the SHT31. With the electronics board these aren't designed to be submitted to chemicals or even outside conditions.

Smart Gadget operating temperature range: -10 to 60 °C
 The Smart Gadget is intended for indoor use only

So, essentially, I have to take their word for it or test it via a side by side comparison, with a good hygrometer, which I don't have and can't seem to find? OK, back to the thread starter...

Do whatever you want I could care less. Destroy as many as you want have fun doing it. 

For the rest of you the boards have been tested.
https://www.wxforum.net/index.php?topic=32439.50

They are within specs repeatability has come into question however.

[kilogulf59]

Do whatever you want I could care less. Destroy as many as you want have fun doing it. 

So what's with the sarcasm? Who said anything about destroying them?

[Old Tele man]

ValentineWeather is the person that I was referring to in my original post:

One of our forum members here has a couple of them that he is comparison testing. The SHT31 is the same sensor chip that's used in current Davis VP2 weather stations.

Do whatever you want I could care less. Destroy as many as you want have fun doing it. 

So what's with the sarcasm? Who said anything about destroying them?

I believe his 'destroying them' humor refers to doing testing that he's already done for us (you). You can do so at your own risk, 'cuz they're not that expensive a loss if it gets salt-corrosion damaged...as his did.

Buy two, test the crap out of one...and...*if* it passes to your satisfaction, ASSUME the second one is equivalently good/accurate.

[ValentineWeather]

Do whatever you want I could care less. Destroy as many as you want have fun doing it. 

So what's with the sarcasm? Who said anything about destroying them?

It was humor, as cheap as they are test them but I'm saying they don't like chemicals. From what I read, in handling instructions for the SHT31 just exposing to scotch tape with the correct storage bag is a no no. Putting them in plastic bag not designed for sensor is bad also. I threw away a couple for this very reason after storing in plastic bag.