8 years ago
#40 Quote
Tdiff is displayed for S-2, S-4, S-5 (Dri Eaz Dehumidifer built in sensor), and S-18 sensors as they are all dual channel sensors.  

  - Tdiff = temperature_this_port - dew_point_that_port
  - if "this port" is channel 1 then Tdiff is channel 1 temperature - channel 2 dew point temperature
  - if "this port" is channel 2 then Tdiff is channel 2 temperature - channel 1 dew point temperature

Tdiff is a computed value that is computed for the 2 channel sensors.  Tdiff will tell you how many degrees your surface is away from the dew point.  If Tdiff is negative your surface temperature is lower than the dew point and condensate is forming.

For example lets say you have a S-2-3 sensor with a A-1 HumiSense probe and you want to monitor the underside of a commercial roof deck for possible condensation.  You would thermally bond the A-1 probe to the roof deck and plug it into port 1 of the S-2-3.  Mount the S-2-3 nearby and about 1 foot below the roof deck such that the built in T/RH sensor inside the S-2-3 which is reported on channel 2 is measuring ambient air T and RH from which it computes the ambient air Dew Point.  The Tdiff reported for channel 1 is then going to be the interesting data as it is the difference between channel 2's dew point and channel 1's temperature, or in other words the temperature difference (Tdiff) between ambient air dew point and the roof deck temperature.  As that difference gets smaller the roof deck temperature is getting closer to the dew point and therefor closer to condensation.  By creating an alarm rule for Tdiff you can be alerted in real time to conditions that can cause condensation.