CB (E7) 06/2018 Page 18/174
1.10 Resistance of the humidity sensor against harmful substances
The following list of harmful substances refers only to the humidity sensor and does not include any other
materials incorporated in the chamber or prohibited substances in relation to explosion protection.
Some gases - especially clean gases - do not have any influence on the humidity sensor. Others do have
a very small influence, whereas others may influence the sensor to a larger extent.
• The following gases do not influence the sensor and the humidity measurement: Argon (Ar), carbon
dioxide (CO
2
),helium (He), hydrogen (H
2
), neon (Ne), nitrogen (N
2
), nitrous oxide (N
2
O), oxygen (O
2
)
• The following gases do not or to a minor extent influence the sensor and the humidity measurement:
Butane (C
4
H
10
), ethane (C
2
H
6
), methane (CH
4
), natural gas propane (C
3
H
8
)
• The following gases do not, or to a minor extent influence the sensor and the humidity measurement,
provided that the indicated loads are not exceeded:
Maximum work place
threshold limit value
Tolerated concentration
with permanent load
These values are to be considered as approximate values. The sensor resistance largely depends on
the temperature and humidity conditions during the time of exposure to harmful substances. Avoid
simultaneous condensation. Tolerated error of measurement: ± 2 %r.H. The maximum work place
threshold limit value is one that can be regarded as harmless for humans.
• Vapors of oil and fat are dangerous for the sensor because they may condensate at the sensor and
thus prevent its function (insulating layer). For similar reasons it is not possible to measure smoke
gases.
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