User's Guide ______________________________________________________________________
16 __________________________________________________________________ M210297EN-E
Beware of Temperature Differences
In humidity measurement and especially in calibration it is essential
that temperature of the probe and measuring environment is the same.
Even a small difference in temperature between the environment and
the probe causes an error. As the curve below shows, if the
temperature is +20 °C and the relative humidity 100 %RH, a
difference of ±1 °C between the environment and the probe causes an
error of ±6 %RH. When the humidity is 90 %RH, the corresponding
error is ±5.4 %RH.
A temperature difference of a few degrees can also cause water to
condense on the sensor surface. HUMICAP
®
®
sensor starts to function
normally as soon as the water has evaporated. If the condensed water
is contaminated, the life span of the probe may shorten and calibration
may change. See also information about sensor preheat, page 36.
0
1
2
3
4
5
6
7
8
9
10
-40
-20
0
20
40
60
80
100
Temperature (°C)
dRH
(
%RH
)
Figure 3
Measurement error at 100 %RH with 1 °C
difference between the ambient and sensor temperature
