Author Topic: Best sensor for a sauna (Read 1497 times)

dunc1ca · « **on:** January 31, 2019, 11:00:41 AM »

I'm wondering if anyone has experience adding a remote thermometer for their sauna. I have a WS-2000 unit which is compatible with the WH31 and WH31B, however they are only rated to up to 60°C. I would prefer something compatible with the weather station but I would consider a stand-alone unit if there is nothing else available. This unit would be subject to temperatures as high as 100°C and very high humidity.

galfert · « **Reply #1 on:** January 31, 2019, 12:29:17 PM »

They are only rated at 60°C because the accuracy is stated as ±0.2°C by Ambient. Above 60°C it still works but then the accuracy suffers a bit more. But it isn't terrible because at 100°C the accuracy is only slightly worse with just ±0.5°C. So it should still work for you. So just because Ambient doesn't report the accuracy at 100°C doesn't mean we can't find out what it is from the manufacture of the sensor. I'm sure your sauna will be okay with ±0.5°C accuracy. If it really matters then you need something with an SHT31 or better like SHT35 or SHT85.

The sensor in these devices is the SHT30 made by Sensirion.

Here are a couple spec sheet data graphs from Sensirion.
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This is a picture I took of my WH32B (same sensor in WH31 or WH31B). You can clearly see the SHT30 stamped on the sensor. This is something my camera picked up but I could not see with the naked eye. This thing is tiny.
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Here you can see how small the SHT30 is.
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As for humidity it wouldn't be high humidity. A sauna has a very low humidity of about somewhere around 5 to 30 percent. A steam room on the other hand has 100 percent humidity. The SHT30 will do very well between 10% to 90% humidity and then the accuracy drops a bit on the high and low end. But it just goes from ±2% to ±4% accuracy. Here are the specs for the SHT30 humidity.
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dunc1ca · « **Reply #2 on:** January 31, 2019, 12:52:39 PM »

Thanks. However, I was under the impression that the WH31/B won't even report anything higher than 60, that the reading would show --- or something to that effect.

galfert · « **Reply #3 on:** January 31, 2019, 12:54:36 PM »

Quote from: dunc1ca on January 31, 2019, 12:52:39 PM

Thanks. However, I was under the impression that the WH31/B won't even report anything higher than 60, that the reading would show --- or something to that effect.

Hmmm good point, it may be software limited. Well you said you already have a WS-2000. So try out the WH32B that came with it and see how high it reports. Let us know.

kbellis · « **Reply #4 on:** February 01, 2019, 08:38:21 AM »

George,

Would you please post a photo of the WH32B illustrating the location of the barometric sensor?

Thanks!!

Kind regards,

Kelly

Sir_MAK · « **Reply #5 on:** February 01, 2019, 08:48:47 AM »

One concern is the lifetime of the sensor in the sauna environment. They are weather resistant, but not weather proof. I am guessing quite a bit of moisture will get inside and may cause issue with the electronics and batteries.

galfert · « **Reply #6 on:** February 01, 2019, 09:18:08 AM »

Quote from: kbellis on February 01, 2019, 08:38:21 AM

George,

Would you please post a photo of the WH32B illustrating the location of the barometric sensor?

Thanks!!

Kind regards,

Kelly

The barometer sensor is the small square silver SMD with the hole in the corner. PCB labeled U2.
I can't say with any certainty but it looks like it's a ~~PBM210 from Pewatron~~
https://www.pewatron.com/en/products/pressure-sensors-load-sensors/product/pbm210/

EDIT: Wrong. See follow up posts. Kelly discovered its a Hoperf HP203N.
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galfert · « **Reply #7 on:** February 01, 2019, 09:27:25 AM »

Quote from: Sir_MAK on February 01, 2019, 08:48:47 AM

One concern is the lifetime of the sensor in the sauna environment. They are weather resistant, but not weather proof. I am guessing quite a bit of moisture will get inside and may cause issue with the electronics and batteries.

High humidity exposure is not a concern in a sauna. A sauna only has between 5% to 30% humidity. A steam room is a different thing. In a steam room there is 100% humidity. A sauna is high heat (up to 212°F) and low humidity. A steam room is lower heat and high 100% humidity. They are opposite. Totally different things.

Sauna ≠ Steam Room

kbellis · « **Reply #8 on:** February 01, 2019, 11:24:13 AM »

Quote from: galfert on February 01, 2019, 09:18:08 AM

The barometer sensor is the small square silver SMD with the hole in the corner. PCB labeled U2.
I can't say with any certainty but it looks like it's a PBM210 from Pewatron
https://www.pewatron.com/en/products/pressure-sensors-load-sensors/product/pbm210/
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Fantastic - thanks!

galfert · « **Reply #9 on:** February 01, 2019, 02:41:25 PM »

Okay people....I did it FOR SCIENCE !!!

Set my oven to 212°F and let it warm up.....tun tun tuuuun!

I placed a piece of cardboard in the oven. Paper burns at 451°F so that's good.

I placed the WH31B in the oven on top of the cardboard.
Most plastic can withstand temperatures higher than 212°F and some as high as 255°F so it should be good.

SMD soldering is done at 600°F so the WH31B printed circuit board and components should be good.

Then I waited for the WH31B to register. It took a couple minutes and it slowly started to register.
(yes my oven window needs cleaning)
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Then it reached 140°F (60°C) Pretty cool so far. No plastic melting.
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Then I saw dashes ---.-°F ....oh oh. I opened the oven door and pulled it out. Test complete. It never registered above 140°F (60°C)
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The WS-2000 display still showed 140°F
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I held the WH31B next to the oven and it still showed dashes for at least a minute.
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But then I noticed something strange. The WS-2000 display tablet showed a new CH8 sensor. I don't have a Channel 8 sensor. So my WH31B which is set for Channel 1 was broadcasting on Channel 1 and 8 at the same time. I could still see CH1 (renamed Master Bedroom). As I watch the temperature go down CH8 kept showing. After the WH31B reached room temperature and I still saw CH8 being broadcast I decided to power down the WS-2000 display tablet and also to pull the batteries from the WH31B. Then put it all back and all seems fine.
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No troubles so far. WH31B looks good. Everything back to normal.

So there you have it. The WH31B is software limited to 140°F (60°C)

kbellis · « **Reply #10 on:** February 01, 2019, 02:50:55 PM »

COOL!

So no broadcast issues inside a metal box? Try the freezer!!

Interesting your oven still had kind of a high humidity with only cardboard and plastic in there.

dunc1ca · « **Reply #11 on:** February 01, 2019, 03:27:06 PM »

Thanks for that. The sauna isn't installed yet so it was good to see. We have a WH31B inside the deep freezer in the garage with no issues. Also, the absolute humidity in your oven went up quite a bit. In the first photo at 125°F (52°C), the dew point was 35°C (95°F). In the second photo, at 140°F (60°C), the dew point was up to 39°C (102°F).

galfert · « **Reply #12 on:** February 01, 2019, 10:53:31 PM »

Yep no problems broadcasting from the metal box oven. But it does have glass window.

Now the Freezer has no window and is also a metal box. So here we go....

Meet the large cold metal box...
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Temperature in the Freezer drawer is -2°F
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Temperature quickly begins to drop
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Sensor is sitting on top of my frozen waffles.
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Within the hour it has adjusted close to the set temperature.
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Dinner came came about and we opened the freezer one too many times and the temperature went up. So we waited till later and finally it reached -2°F
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galfert · « **Reply #13 on:** February 01, 2019, 10:56:19 PM »

And for verification I used my trusty Fluke 87V with thermocoupler
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Fridge Settings
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kbellis · « **Reply #14 on:** February 03, 2019, 08:12:39 AM »

ooo, nice fridge!

Thanks for sharing and testing

kbellis · « **Reply #15 on:** April 28, 2019, 05:26:35 PM »

Quote from: galfert on February 01, 2019, 09:18:08 AM

I can't say with any certainty but it looks like it's a PBM210 from Pewatron
https://www.pewatron.com/en/products/pressure-sensors-load-sensors/product/pbm210/

Hello George,

Just curious, were there any markings or other extrinsic evidence that suggested the name of the manufacturer and model of the barometric sensor in the WH32B? After studying your photo, I was unable to determine any stamped markings on the little square metal enclosure.

Thank you for all of your great information!

Kind regards,

Kelly

Bushman · « **Reply #16 on:** April 28, 2019, 06:54:04 PM »

I use the Wirelesstags (as shown in my sig) for the hot tub and sauna and fridge. (I get a small referral fee - full disclosure). Highly accurate.

galfert · « **Reply #17 on:** April 28, 2019, 07:48:11 PM »

Quote from: kbellis on April 28, 2019, 05:26:35 PM

Quote from: galfert on February 01, 2019, 09:18:08 AM
I can't say with any certainty but it looks like it's a PBM210 from Pewatron
https://www.pewatron.com/en/products/pressure-sensors-load-sensors/product/pbm210/

Hello George,

Just curious, were there any markings or other extrinsic evidence that suggested the name of the manufacturer and model of the barometric sensor in the WH32B? After studying your photo, I was unable to determine any stamped markings on the little square metal enclosure.

Thank you for all of your great information!

Kind regards,

Kelly

There are no markings at all. I looked under pretty good magnification lens and found nothing on it. That does seem strange doesn't it.

kbellis · « **Reply #18 on:** April 29, 2019, 07:04:19 AM »

So how'd you come up with a PBM210, or even Pewatron?

galfert · « **Reply #19 on:** April 29, 2019, 07:13:19 AM »

I spent a lot of time looking at all the barometric parts available in Digikey and Mouser. It was the only thing that looked like what was inside the WH32B. That is why I said I couldn't say it with certainty.

galfert · « **Reply #20 on:** April 29, 2019, 07:27:51 AM »

Also from Pewatron's product page you can see that their product markings are on the bottom of the SMD.

EDIT: Turns out the barometric sensor is actually a Hoperf HP203N. See below posts and follow my link to Kelly's post. You need a microscope to see the markings. A magnify lens as I used is not good enough.

kbellis · « **Reply #21 on:** April 29, 2019, 07:32:29 AM »

Good enough. Thanks for the diligence and your kind reply George!

galfert · « **Reply #22 on:** April 30, 2019, 07:51:48 AM »

Thanks Kelly for the better detective work than mine, and finding out the barometric sensor is actually a Hoperf HP203N.

https://www.wxforum.net/index.php?topic=36781.0

News:

Author Topic: Best sensor for a sauna (Read 1497 times)