
Feature
Warmed probe
Chemical purge
Extra heat (Xheat)
Notes
Requires an additional
temperature probe for
relative humidity
measurement.
Data is locked during
heating and cooling.
Not for use in freezing
temperatures.
For use before relative
humidity calibration and
adjustment.
Data is locked during
heating and cooling.
Warmed probe, chemical purge and extra heat are optional features available for
probes with composite sensors (HUMICAPR2C, HUMICAP180RC and
HUMICAP180C).
More information
‣
‣
Chemical purge option (page 14)
‣
Extra sensor heating (Xheat) option (page 16)
2.3.1 Warmed probe option
The warmed probe is suitable for climates with high humidity. It is ideal for tropical, coastal,
and marine installations. It helps the sensor stay dry reducing the chemical contamination and
minimizing drift.
In changing temperatures with high humidity, the probe temperature can lag behind the
temperature of the surrounding air causing a risk of condensation on the sensor. A wet probe
cannot observe the actual humidity in the ambient air. If the condensed water is contaminated,
the life span of the probe may shorten and the calibration change.
The temperature of a warmed probe is always higher than that of the environment. This
prevents condensation on the probe. With the additional temperature probe it is possible to
calculate the true RH based on the non-heated (ambient) temperature information. If you have
selected warming but the additional temperature probe is not present, HMP155 only produces
dew point and mixing ratio output.
The warmed probe function works with 12 VDC but the heating starts slower. For optimal
heating with the warmed probe function, use 16 VDC.
2.3.2 Chemical purge option
The chemical purge option suits installation locations that are exposed to chemical pollution,
such as chemical plants and roads.
HMP155 User Guide
M210912EN-D
14
Содержание HUMICAP HMP155
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