Method and detector for measurement of relative humidity by using a combination of capacitive humidity detectors (101,102;10P), in particular in radiosondes. In the detector, between the capacitor plates, a material (12) is used, the permittivity of which is a function of the amount of water absorbed by said material (12). In the method said detector (10) or combination of detectors is heated in order to remove any ice, frost or condensed humidity deposited on the face and/or in the environment of the detector. The detector capacitance (CM) or a part (C1...CN) of same is heated, in time and/or in place, periodically by conducting an electric current (I) through one or several heating resistors (R), and the detecting of the detector capacitance (CM) is carried out without measurement of the detector temperature after the detector capacitance or a part (C1...CN) of same has cooled down substantially to the temperature of the environment. In the method, two or more separate detectors (101,102) or a coupling of several component detectors (C1...CN) in parallel, or equivalent is employed. When several separate detectors (101,102) are used, each detector is heated in its turn, and the relative humidity is detected primarily on the basis of a detector (101,102) or its component detectors (C1...CN) that has/have cooled sufficiently after said heating.
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