Humidity sensor

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Dear all
I want to know if you know a humidity sensro that can work to -80°C, I want to use it to calculate dew point.
any suggestions are welcome.

I love Digital
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I would expect at -80c that there would be little humidity due to any water vapour being frozen.

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Ali_dehbidi wrote:
sensro that can work to -80°C, I want to use it to calculate dew point.

http://en.wikipedia.org/wiki/Tri...
Could you tell us at what pressures H2O is still in liquid phase at -80degC?

Preparing for a longer journey?

No RSTDISBL, no fun!

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Quote:
Could you tell us at what pressures H2O is still in liquid phase at -80degC?

There are some devices that they sell. See this
http://www.vaisala.com/en/produc...

The problem is the price!
So do you happen to know something way cheaper, if I could sense humidity then there are lots of cheap ways to measure temperature and finally calculating dew point.

I love Digital
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Brutte wrote:

http://en.wikipedia.org/wiki/Tri...
Could you tell us at what pressures H2O is still in liquid phase at -80degC?

Even at well below the triple point, water still exerts a non-zero vapour pressure, which means that humidity will quite happily form at any pressure (1), including standard atmospheric pressure. For example, at the bizarrely named Troll Station, there is humidity:

http://www.wunderground.com/glob...

But back to the OP, UPSI in France claims to have capacitive sensors that work down to -90 C:

http://upsi.fr/products/sensor.html

Sorry, I don't know the price for their sensors.

- S

(1) Funny things happen at above the critical pressure, so YMMV there.

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That's an industrial scale sensor, even NIST traceable. I guess that makes it slightly more expensive than the sensor used in my $10 'weather' station...

You are probably looking for something like this.

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jayjay1974 wrote:
That's an industrial scale sensor, even NIST traceable. I guess that makes it slightly more expensive than the sensor used in my $10 'weather' station...

You are probably looking for something like this.


The sensor linked, specified with "Operating Temperature Range: 0°C to +60°C", is not even close to the OP's requirement.
Quote:
I want to know if you know a humidity sensro that can work to -80°C

For pricing, some of the UPSI sensors are available at Saelig and seem quite reasonable.

Stan

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Quote:
For pricing, some of the UPSI sensors are available at Saelig and seem quite reasonable.

Which model do you suggest? I have seen all of them, and none of them seems to work till -80°C,
Most of them work till -40°C ,And I think for -40 I can use SHT75..It’s way more cheaper and more accurate!

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I overlooked the -80 requirement. In what application does it get so cold?

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Quote:
overlooked the -80 requirement. In what application does it get so cold?

In military warheads! :D

In some food processing systems, In some air conditioners, etc...

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Quote:
In military warheads! [smile]

Careful, Ali! You might easily be taken seriously. Fair or not, your country-of-origin will likely make a lot of people nervous.

"Ziggy really sang, screwed up eyes and screwed down hairdo. Like some cat from Japan, he could lick 'em by smiling. He could leave 'em to hang. He came on so loaded man, well [..] and snow white tan. [Bowie]

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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I had a good laugh, .... I like that kind of humor :)

Dragon broken ? Or problems with the Parallel Port Programmer ? Scroll down on my projects-page http://www.aplomb.nl/TechStuff/TechStuff.html for tips

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Quote:
Careful, Ali! You might easily be taken seriously. Fair or not, your country-of-origin will likely make a lot of people nervous.

lol...if you smile the world reflection would be a smile!
Like plons respnose.

I love Digital
and you who involved in it!

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Ali_dehbidi wrote:
Quote:
For pricing, some of the UPSI sensors are available at Saelig and seem quite reasonable.

Which model do you suggest? I have seen all of them, and none of them seems to work till -80°C,
Most of them work till -40°C ,And I think for -40 I can use SHT75..It’s way more cheaper and more accurate!

From the Saelig link navigate: Components/Sensors/Ambient

These three are specified: "Ambient temperature (AT) from -90°C to 85°C"
- UPSI G-US.12 Very Low Temperature Humidity Sensor US$6.77
- UPSI G-US.13 Plugable Low Temperature Sensor US$8.05
- UPSI G-TUS.13 Dual Channels Low Temperature Sensor US$8.38

Stan

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But what is your application?

I witnessed a few HALT tests where a product is mercilessly tortured with vibrations (random up to 80Grms) and temperature variations. To get low temperatures quickly (> 65C/min) it uses liquid nitrogen. I saw peak temperatures of -100degC.

Quite a cool machine ;)

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Quote:
From the Saelig link navigate: Components/Sensors/Ambient

These three are specified: "Ambient temperature (AT) from -90°C to 85°C"
- UPSI G-US.12 Very Low Temperature Humidity Sensor US$6.77
- UPSI G-US.13 Plugable Low Temperature Sensor US$8.05
- UPSI G-TUS.13 Dual Channels Low Temperature Sensor US$8.38

Stan


Thanks stan.

I love Digital
and you who involved in it!

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JohanEkdahl wrote:
Quote:
In military warheads! [smile]

Careful, Ali! You might easily be taken seriously. Fair or not, your country-of-origin will likely make a lot of people nervous.

Somehow, I can't imagine a defence contractor asking for technical help on avrfreaks.

jayjay1974 wrote:
But what is your application?

Well, food processing was mentioned, and -80C is the sublimation temp for dry ice, so my guess would be ice cream:

http://www.itv.com/food/recipes/...

Incidentally, for the OP, you mentioned this sensor:

http://www.vaisala.com/en/produc...

Although it's speced for a dew point of -80C, its ambient temp rating only goes down to -40C. If your ambient requirements are only -40C, then there are many humidity sensors that work at that temp, including the sensiron SHTx and the measurement specialties sensors:

http://www.meas-spec.com/humidit...

- S

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Quote:
Somehow, I can't imagine a defence contractor asking for technical help on avrfreaks.

Neither can I. Others might, and that was my point.

"Ziggy really sang, screwed up eyes and screwed down hairdo. Like some cat from Japan, he could lick 'em by smiling. He could leave 'em to hang. He came on so loaded man, well [..] and snow white tan. [Bowie]

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]