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5.3
Adjustment behaviour of the sensor
In humidity and temperature measurement, several parameters are responsible for the
adjustment behaviour (time until the actual measuring value is displayed). The para-
meter responsible for the highest measuring error is a temperature discrepancy
between the sensor resp. the whole measuring instrument and the material being
measured resp. the air.
Therefore, allow your humimeter device to adjust until the displayed temperature
corresponds to the actual temperature. The graph below shows how long it takes to
adjust from 20 °C to 30 °C.
To demonstrate the importance of temperature adjustment, the table below shows the
measuring errors due to a temperature difference between the measuring instrument
and the material being measured of only 1 °C / 1.8 °F, at different ambient tempera-
tures.
0.1 aw
10 °C (50 °F)
20 °C (68 °F)
30 °C (86 °F)
+/- 0.007 aw
+/- 0.006 aw
+/- 0.006 aw
0.5 aw
+/- 0.035 aw
+/- 0.032 aw
+/- 0.03 aw
0.9 aw
+/- 0.063 aw
+/- 0.057 aw
+/- 0.054 aw
At room temperature (20 °C / 68 °F) and an assumed water activity of 0.5, a tempera-
ture difference between the sensor and the material being measured of 1 °C / 1.8 °F
causes a measurement error of 0.032 aw. A temperature difference of 3 °C / 5.4 °F
would cause a measurement error of more than 0.1 aw.