Method and arrangement in measurement of humidity, in particular in radiosondes

Method for measurement of relative humidity by using a humidity detector (14), in particular in radiosondes (100), in which humidity detector (14) an active material is used whose electric properties are a function of the amount of water absorbed by said material, in which method said detector (14) is heated so as to remove any ice, frost or condensed humidity gathered on its face or in its vicinity, in which method the temperature (T) of the humidity detector (14) and of the ambient temperature (T.sub.a) are detected by appropriately positioned temperature detectors and these quantities are utilized along with the differences between both such temperatures as correction factors or compensation values in the computing of the humidity measurement values (U), and in which method the humidity detector (14) is protected by means of a mechanical shield construction (10) arranged around the detector, chacterized in that said shield construction (10) is heated to a temperature higher than the ambient temperature so that no substantial condensing or freezing of humidity takes place on the humidity detector (14) or on the structures in the vicinity of same.