Capacitance type moisture sensor and method of producing the same

A capacitance type moisture sensor comprising:

• a sensor housing having an electrically-insulating wall, an outer surface of said electrically-insulating wall facing a space where amounts of water should be detected;
• a pair of electrodes disposed on said sensor housing, at least one of which is formed on an inner surface of said electrically-insulating wall, electric field developed between said electrodes being defined as a moisture detecting region;
• and
• a circuit unit including a capacitance detecting circuit for detecting a capacitance value between said electrodes, which changes in response to the amounts of water in said moisture detecting region, and an output circuit for providing an electrical signal corresponding to the amounts of water according to the capacitance value detected by said capacitance detecting circuit,
• wherein said pair of electrodes are composed of a ring-shaped electrode having an open center and a central electrode, which is disposed in the open center of said ring-shaped electrode such that an outer circumference of said central electrode is spaced from an inner circumference of said ring-shaped electrode by a constant distance.

A capacitance type moisture sensor comprising:

• a sensor housing having an electrically-insulating wall, an outer surface of said electrically-insulating wall facing a space where amounts of water should be detected;
• a pair of electrodes disposed on said sensor housing, at least one of which is formed on an inner surface of said electrically-insulating wall, electric field developed between said electrodes being defined as a moisture detecting region;
• and
• a circuit unit including a capacitance detecting circuit for detecting a capacitance value between said electrodes, which changes in response to the amounts of water in said moisture detecting region, and an output circuit for providing an electrical signal corresponding to the amounts of water according to the capacitance value detected by said capacitance detecting circuit,
• wherein said sensor housing has a concave formed in an inner surface of a bottom wall thereof, and a convex formed on an outer surface of the bottom wall at a position opposed to said concave, and wherein a bottom surface of said concave is the inner surface of said electrically-insulating wall and a top surface of said convex is the outer surface of said electrically-insulating wall,
• said capacitance type moisture sensor further comprising an electric wave shield layer formed by depositing a metal material on an internal surface of said sensor housing other than said concave, and wherein said shield layer is connected to a zero-voltage point of said capacitance detecting circuit.