Self Adjustment Of Testo 6615 Trace Humidity Probe - TESTO 6381 Instruction Manual

4 Transmitter
4.3.4.13.

Self adjustment of testo 6615 trace humidity probe

Conventional trace humidity probes show a steep rise in measuring
uncertainty at low humidities. In the testo 6615 trace humidity
probe, these measuring uncertainties are corrected by means of an
automatic self-adjustment process. This means that extremely
accurate measuring results are also attained to -60 °C
To this end, a temperature sensor is fitted on the back of the
testo 6615 which is used as a heater. A humidity and temperature
value pair is taken in both the unheated and heated state. The
deviation of the probe obtained from these pairs of values is
automatically corrected.
The graph shows the effect of the self-adjustment, e.g. during the
Init. phase.
1 Self-adjustment
2 Correction of measurement value
3 Process dew point temperature
For the effectiveness of the self-adjustment the following
prerequisites are decisive over the duration of the self-adjustment.
• The process temperature should not vary by more than 0.5K
• The dew point temperature should remain stable, as far as
possible
• The process pressure should not vary excessively
60
If these prerequisites cannot be fulfilled, the values
obtained during the last successful self-adjustment will be
maintained.
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