Abstract: A dry/dew/frost sensor comprising a plurality of sensor units, each sensor unit comprising a ceramic substrate (1, 2) whose permittivity is lower than ice and a pair of electrodes (3, 4; 5, 6) being arranged on the ceramic substrate in contact therewith, wherein adjacent sensor units are arranged so as to face each other at a predetermined distance so that the pair of electrodes (3, 4; 5, 6) may be opposed to each other, and the impedance between the pair of electrodes on each of the sensor unit varying with changes in three states, dry, bedewed, and frosted states.

Abstract: A humidity sensitive resistor, comprising a pair of detecting electrodes (2) and (3) formed on an insulating substrate (1), and a humidity sensitive film (4) formed to coat on this detecting electrodes, the humidity sensitive film (4) being made of an integrated structure of a first layer macromolecular resin film (5) containing a polyvinyl alcohol polymer and an electrolyte and a second layer of hygroscopic macromolecular resin film (6) covering on the surface of the first layer, and humidity being detected with the aid of a change of the resistance value of this humidity sensitive film (4).