Forum Menu




 


Log in Problems?
New User? Sign Up!
AVR Freaks Forum Index

Post new topic   Reply to topic
View previous topic Printable version Log in to check your private messages View next topic
Author Message
Ali_dehbidi
PostPosted: May 12, 2012 - 11:09 AM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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
and you who involved in it!
 
 View user's profile Send private message  
Reply with quote Back to top
Kartman
PostPosted: May 12, 2012 - 01:10 PM
10k+ Postman


Joined: Dec 30, 2004
Posts: 11126
Location: Melbourne,Australia

I would expect at -80c that there would be little humidity due to any water vapour being frozen.
 
 View user's profile Send private message  
Reply with quote Back to top
Brutte
PostPosted: May 12, 2012 - 02:39 PM
Raving lunatic


Joined: Oct 05, 2006
Posts: 3069
Location: Poland

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?

_________________
No RSTDISBL, no fun!
 
 View user's profile Send private message  
Reply with quote Back to top
Ali_dehbidi
PostPosted: May 13, 2012 - 06:06 AM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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.

_________________
I love Digital
and you who involved in it!
 
 View user's profile Send private message  
Reply with quote Back to top
mnehpets
PostPosted: May 13, 2012 - 04:07 PM
Resident


Joined: Nov 09, 2011
Posts: 591


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.
 
 View user's profile Send private message  
Reply with quote Back to top
jayjay1974
PostPosted: May 14, 2012 - 12:57 AM
Raving lunatic


Joined: Oct 30, 2002
Posts: 5764
Location: The Netherlands

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.
 
 View user's profile Send private message  
Reply with quote Back to top
sbennett
PostPosted: May 14, 2012 - 03:18 AM
Posting Freak


Joined: Nov 19, 2001
Posts: 1008
Location: San Luis Obispo

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
 
 View user's profile Send private message  
Reply with quote Back to top
Ali_dehbidi
PostPosted: May 14, 2012 - 09:42 AM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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!

_________________
I love Digital
and you who involved in it!
 
 View user's profile Send private message  
Reply with quote Back to top
jayjay1974
PostPosted: May 14, 2012 - 12:33 PM
Raving lunatic


Joined: Oct 30, 2002
Posts: 5764
Location: The Netherlands

I overlooked the -80 requirement. In what application does it get so cold?
 
 View user's profile Send private message  
Reply with quote Back to top
Ali_dehbidi
PostPosted: May 14, 2012 - 01:21 PM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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

In military warheads! Very Happy

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

_________________
I love Digital
and you who involved in it!
 
 View user's profile Send private message  
Reply with quote Back to top
JohanEkdahl
PostPosted: May 14, 2012 - 02:52 PM
10k+ Postman


Joined: Mar 27, 2002
Posts: 21408
Location: Lund, Sweden

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.
 
 View user's profile Send private message Visit poster's website 
Reply with quote Back to top
Plons
PostPosted: May 14, 2012 - 03:51 PM
Raving lunatic


Joined: Nov 01, 2005
Posts: 6597
Location: Hilversum - the Netherlands

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

_________________
Dragon broken ? Or problems with the Parallel Port Programmer ? Scroll down on my projects-page http://www.aplomb.nl/TechStuff/TechStuff.html for tips
 
 View user's profile Send private message Visit poster's website 
Reply with quote Back to top
Ali_dehbidi
PostPosted: May 14, 2012 - 04:46 PM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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!
 
 View user's profile Send private message  
Reply with quote Back to top
sbennett
PostPosted: May 14, 2012 - 07:43 PM
Posting Freak


Joined: Nov 19, 2001
Posts: 1008
Location: San Luis Obispo

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
 
 View user's profile Send private message  
Reply with quote Back to top
jayjay1974
PostPosted: May 14, 2012 - 11:37 PM
Raving lunatic


Joined: Oct 30, 2002
Posts: 5764
Location: The Netherlands

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 Wink
 
 View user's profile Send private message  
Reply with quote Back to top
Ali_dehbidi
PostPosted: May 15, 2012 - 06:08 AM
Posting Freak


Joined: Dec 22, 2005
Posts: 1329
Location: shiraz , iran

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!
 
 View user's profile Send private message  
Reply with quote Back to top
mnehpets
PostPosted: May 15, 2012 - 08:07 AM
Resident


Joined: Nov 09, 2011
Posts: 591


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
 
 View user's profile Send private message  
Reply with quote Back to top
JohanEkdahl
PostPosted: May 15, 2012 - 09:01 AM
10k+ Postman


Joined: Mar 27, 2002
Posts: 21408
Location: Lund, Sweden

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.
 
 View user's profile Send private message Visit poster's website 
Reply with quote Back to top
Display posts from previous:     
Jump to:  
All times are GMT + 1 Hour
Post new topic   Reply to topic
View previous topic Printable version Log in to check your private messages View next topic
Powered by PNphpBB2 © 2003-2006 The PNphpBB Group
Credits