Patent ID: 7791356

Claim:
A capacitive proximity switch, comprising: an electrically insulating cover plate having a front surface; an electrically conductive sensor surface covered by said cover plate, said sensor surface serving as a part of a capacitor having a capacitance that varies with proximity; a reference sensor surface for generating a reference signal for a determination of an actuation state of the proximity switch, wherein signal components of a reference signal are proportional to a capacitance of a reference capacitor formed with said reference sensor surface, and wherein the capacitance of the reference capacitor is determined by ambient conditions at said sensor surface; a common substrate disposed at a spacing distance from said cover plate and carrying said reference sensor surface and said sensor surface in common; an electrically conductive body disposed between said cover plate and said substrate, spanning said spacing distance between said substrate and said cover plate, and being electrically connected to said sensor surface and/or forming at least a part of said sensor surface with a portion of a surface thereof; wherein said reference sensor surface is insulated against electrical charges and/or changes in a charge at said front side of said cover plate by an air layer formed by said spacing distance between said substrate and said cover plate.