The values of output parameters that are dependent on temperature measurement (such as
relative humidity) are unavailable when the probe is warming itself, unless the true
temperature of the measured environment is updated to the temperature compensation
register of the probe from another measurement instrument (for example, TMP1 model probe).
Output parameters that can be measured or calculated without this external temperature
information, such as dew point temperature, are available even without the temperature input.
Indigo500 transmitters support HMP7 temperature compensation from TMP1. For more
information, see Indigo520 User Guide (M212287EN).
HMP7 in fuel cell applications
Probe heating makes HMP7 ideal for use in fuel cell applications, specifically proton-exchange
membrane fuel cells (PEMFC). Humidity measurements in fuel cell applications are performed
in a high-humidity environment, typically over 80% relative humidity. Performing humidity
measurements in hot, near-condensing environments is a challenging task, and the humidity
sensor must be adequately protected against saturation to allow continuous measurement.
Probe heating accomplishes just that.
HMP7 can be ordered from Vaisala with special settings that have been optimized for the fuel
cell application. These settings include a faster probe heating control that allows the probe to
quickly heat the probe to stay ahead of the rising dew point temperature.
HMP7 is not designed for use in hazardous environments with
potentially explosive atmospheres. Make sure no part of the probe is placed in
a potentially explosive gas mixture.
WARNING!
More information
‣
Mounting probe head inside DTR502B (page 38)
HMP Series with MMP8 and TMP1 User Guide M212022EN-F
28
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