Capacitive humidity transducer

Claim 1

In a capacitive humidity transducer, electrically non-conductive base means having an outer supporting surface, at least a pair of electrically conductive coatings carried by said base means at said outer supporting surface thereof, said electrically conductive coatings being spaced from each other and being passive with respect to water absorption, dielectric film means also carried by said surface of said base means, said dielectric film means covering at least a portion of said electrically conductive coatings and being composed at least in part of a film which is active with respect to water absorption and which has a dielectric constant which changes as a function of the amount of water absorbed thereby, and an outer, thin, electrically conductive, water-permeable layer carried on the outer surface of said dielectric film means, said layer because of its water permeability permitting moisture in the atmosphere to reach said dielectric film means which is situated at least in part between said electrically conductive coatings and said electrically conductive water permeable layer, said dielectric film means maintaining said electrically conductive water permeable layer out of contact with at least a portion of one of said electrically conductive coatings to form a capacitor therebetween, another portion of said electrically conductive coatings and a portion of said electrically conductive water permeable layer being in contact with each other to form an electrical connection so that said capacitor can be connected to measuring means for indicating atmospheric humidity, said capacitor being supported in its entirety by said base means which provides a stable support for said capacitor enabling said dielectric film means to provide a rapid response to changes in humidity under a wide variety of atmospheric conditions.