MOISTURE SENSOR

PURPOSE:To obtain a sensor having high film strength, excellent responsiveness, etc. without clogging of fine holes by suspended dust by using a dustproof film which consists of a hydrophilic org. high polymer film incorporated with fibers as aggregate and allows transmission of moisture but prohibits permeation of liquid water to coat a moisture sensitive element. CONSTITUTION:A mixed soln. composed of cellulose acetate having about 55% rate of acetylation and plasticizer is impregnated with fibers of Japanese paper, etc. and is dried to manufacture a moisture permeable dustproof film. On the other hand a moisture sensitive element 2 obtd. by impregnating a surface active agent with the porous ceramics obtd. by calcining a mixture composed of silicon carbide and borosilicate zinc glass is prepd. The surface of the elemen 2 is coated by said film 3 by which a moisture sensor 1 is obtd. The film 3 has such pores which allow permeation of liquid water and allows permeation of only the steam. The sensor having good responsiveness without closing of the pores by suspended dust and without change in the mositure sensing characteristic for a long period of time is obtd.