Method for measurement of relative humidity, in particular in radiosondes, and humidity detectors that make use of the method

Method for measurement of relative humidity by using a capacitive humidity detector (10), in particular in radiosondes, in which detector, between capacitor plates with each capacitor plate connected to a different output terminal, an insulating material ( 12 ) is used whose permittivity is a function of the amount of water vapor absorbed by said insulating material (12), and in which method said detector capacitance (C.sub.M) is heated, in time, periodically by means of electric current (I) in order to reduce or remove the adverse effects of any ice, frost, or condensed humidity deposited on the face or in the environment of the detector, in which method the detecting of the detector capacitance (C.sub.M) is carried out without measurement of the detector temperature after detecting the capacitance between the output terminals, and in which method the heating period (t.sub.o) of the detector is a fraction of the measurement cycle T.sub.o of the detector, and the detecting (t.sub.3 . . . t.sub.4) of the detector capacitance (C.sub.M) is carried out after the heating cycle (t.sub.o) in the final stage of the measurement cycle T.sub.o after the detector (10) has had time to be stabilized after said heating period (to) and to cool down substantially to the temperature of its environment, at which time the detector shows a correct humidity reading (RH.sub.M), where the method is characterized in that:

• the ratio of the duration of the measurement cycle T.sub.o to the duration of the heating cycle t.sub.o is selected from the range of T.sub.o /t.sub.o =10 . . . 3000.