Vaisala Oy

Hannu Jauhiainen

Lars Stormbom

Jorma Ponkala

Ari Paukkunen

Veijo Antikainen

Method, in particular in radiosondes, for measurement of relative humidity by using a capacitive humidity detector (10) or a combination of detectors (10.sub.1,10.sub.2 ;10P), as well as humidity detectors. In the detector, between the capacitor plates, an insulating material (12) is used, whose permittivity is a function of the amount of water vapor absorbed by the insulating material (12). The detector (10) or the 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 (C.sub.M) or a part (C.sub.1 . . . C.sub.N) of same is heated, in time and/or in place, periodically by means of electric current (I). The detecting of the detector capacitance (C.sub.M) is carried out without measurement of the detector temperature after the detector capacitance or a part (C.sub.1 . . . C.sub.N) of same has cooled down substantially to the temperature of the environment where the ratio of the duration of the measurement cycle to the duration of the heating cycle is selected from a minimum range of 10 to one, up to a maximum range of 3000 to one.

Method for measurement of relative humidity, in particular in

Method, in particular in radiosondes, for measurement of relative humidity by using a capacitive humidity detector (10) or a combination of detectors (10.sub.1, 10.sub.2 ; 10P), as well as humidity detectors. In the detector, between the capacitor plates, an insulating material (12) is used, whose permittivity is a function of the amount of water absorbed by the insulating material (12). The detector (10) or the 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 (C.sub.M) or a part (C.sub.1 . . . C.sub.N) of same is heated, in time and/or in place, periodically by means of electric current (I). The detecting of the detector capacitance (C.sub.M) is carried out without measurement of the detector temperature after the detector capacitance or a part (C.sub.1 . . . C.sub.N) of same has cooled down substantially to the temperature of the environment.

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Espoo, Finland

Hannu Jauhiainen