TESTO 6681 Instruction Manual page 65

1.3.5.5 High-humidity adjustment for testo 6614
Mollier diagram
"Microclimate"
sensor conditions
After heating
With the testo 6614, the rear of the Testo humidity sensor is heated, creating
a microclimate around the sensor (within the filter) that is constantly 5 K
warmer than the actual process conditions. As can be seen in the Mollier
diagram, this reduces the relative humidity at the sensor from around
100 % RH to a lower value, e.g. 73 % RH. In this range, the reaction time of
the sensor is noticeably shorter than in the condensation range and the risk
of the sensor corroding is also reduced. Using the separate temperature
probe, the testo 6681 transmitter compensates the microclimate conditions
and displays the process readings.
The reference conditions (11.3 % RH and 75.3 % RH) for the
2-point adjustment of the testo 6614 should be generated in a
humidity generator, as humidity adjustment sets cannot be
used due to the heat generated. The adjustment can also be
carried out at a third adjustment point (90 % RH) by Testo
Service so that optimum accuracy is also achieved in the high
humidity ranges.
testo 6681 Ethernet
e.g. 73 % RH
100 % RH
High-humidity process
conditions
Mist
- 1.3 Commissioning 65