Vaisala HUMICAP HMP155, User Manual, Page: 15 / 102

2.2 HMP155 parts
Figure 1 HMP155 parts
1 8-pin male connector (M12)
2 Protective cover
3 Plastic part of filter
4 Filter
2.3 Heating options
HMP155 offers 3 heating options. The following table describes the options, their benefits, and
typical applications.
Table 10 Heating options
Feature Warmed probe Chemical purge Extra heat (Xheat)
Type Continuous probe heating Periodical heating of
humidity sensor Triggered heating on
humidity sensor
Description Keeps the relative humidity
of the humidity sensor
below 80 %RH in all
circumstances by heating
the probe. Cleans the humidity sensor
regularly, for example by
heating to 180 °C for 6 min
every 0.5 … 10 days (user
configurable). Heats the humidity
sensor chip to 100 °C
(212 °F) for 30 s, if the
sensor humidity is >
95 %RH (user
configurable).
Benefits Accurate measurement in
high humidity climate by
avoiding condensation on
the probe. Reduced drift by removing
chemical vapors from the
sensor polymer. Rapidly drying water
vapor or droplets in
humidity sensor.
Where used High humidity climates,
such as tropical, coastal,
and marine installations
Installation location
exposed to chemical
pollution, such as roads
and chemical plants Industrial applications
where there is a risk that
the humidity sensor
becomes too wet (for
example, installation
without a radiation
shield).
Chapter 2 – Product overview
13