In humidity measurement and especially in calibration, it is essential that the temperature of the probe and the measurement environment are the same. Even a small temperature difference between the environment and the probe causes an error. As the curve in the following figure shows, if the temperature is +20 °C and relative humidity is 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. The 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.
