dave,
thanks for the documentation : I red this documents but I still do not undrstand the reason for which rh is normally distribuited even under 0 degC.
Please see this US weather condition in Alaska:
Anchorage, Alaska, United States

* Weather overview
* Two-week forecast
* Hour-by-hour
* Past week
* °F
* °C

Current Time marted 30 novembre 2010, 12.29.06 AKST
Current conditions
Sunny. Cold. -6 °C
Sunny. Cold.
Change to Fahrenheit
Sunny. Cold.
Location: Merrill Field
Temperature: -6 °C
Comfort level: -8 °C
Dew point: -15 °C
Barometer: 1005 millibars
Humidity: 48%
Visibility: 16 km
Wind: 6 km/h from 300° West-northwestDirection East-southeast
Last update: mar 11.53 AKST

They are saying -6°C 48%rh and -15°C dew point.

Could you please spend few more words in order for me to understand this point ?
Thanks
Regards,
Ambrogio
IW2FVO
73!



Quote Originally Posted by Dave View Post
iw2fvo , I have no idea where you got the calculation you are using but the calculation is different for relative humidity ABOVE ICE.. The calculation you are using is for ABOVE WATER. Please read this artical from the people that make the sensor you are trying to use....

http://www.sensirion.com/en/pdf/prod...Humidity_E.pdf

Dave Purola,
N8NTA