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 Posted: May 12, 2012 - 11:09 AM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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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. |
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Posted: May 12, 2012 - 01:10 PM |
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Joined: Dec 30, 2004
Posts: 8730
Location: Melbourne,Australia
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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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Posted: May 12, 2012 - 02:39 PM |
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Joined: Oct 05, 2006
Posts: 2242
Location: Poland
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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/Triple_point
Could you tell us at what pressures H2O is still in liquid phase at -80degC?
Preparing for a longer journey? |
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Posted: May 13, 2012 - 06:06 AM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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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/products/dewp ... MT152.aspx
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. |
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Posted: May 13, 2012 - 04:07 PM |
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Joined: Nov 09, 2011
Posts: 396
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Brutte wrote:
http://en.wikipedia.org/wiki/Triple_point
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/global/stations/89504.html
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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Posted: May 14, 2012 - 12:57 AM |
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Joined: Oct 30, 2002
Posts: 5718
Location: The Netherlands
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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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Posted: May 14, 2012 - 03:18 AM |
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Joined: Nov 19, 2001
Posts: 917
Location: San Luis Obispo
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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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Posted: May 14, 2012 - 09:42 AM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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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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Posted: May 14, 2012 - 12:33 PM |
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Joined: Oct 30, 2002
Posts: 5718
Location: The Netherlands
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| I overlooked the -80 requirement. In what application does it get so cold? |
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Posted: May 14, 2012 - 01:21 PM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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Quote:
overlooked the -80 requirement. In what application does it get so cold?
In military warheads! 
In some food processing systems, In some air conditioners, etc... |
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Posted: May 14, 2012 - 02:52 PM |
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Joined: Mar 27, 2002
Posts: 18531
Location: Lund, Sweden
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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. |
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Posted: May 14, 2012 - 03:51 PM |
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Joined: Nov 01, 2005
Posts: 6323
Location: Hilversum - the Netherlands
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Posted: May 14, 2012 - 04:46 PM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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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. |
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Posted: May 14, 2012 - 07:43 PM |
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Joined: Nov 19, 2001
Posts: 917
Location: San Luis Obispo
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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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Posted: May 14, 2012 - 11:37 PM |
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Joined: Oct 30, 2002
Posts: 5718
Location: The Netherlands
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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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Posted: May 15, 2012 - 06:08 AM |
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Joined: Dec 22, 2005
Posts: 1261
Location: shiraz , iran
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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. |
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Posted: May 15, 2012 - 08:07 AM |
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Joined: Nov 09, 2011
Posts: 396
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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/hestons ... -ice-cream
Incidentally, for the OP, you mentioned this sensor:
http://www.vaisala.com/en/products/dewp ... MT152.aspx
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/humidity-senso ... nents.aspx
- S |
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Posted: May 15, 2012 - 09:01 AM |
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Joined: Mar 27, 2002
Posts: 18531
Location: Lund, Sweden
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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. |
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