US Patent 7791356 Capacitive proximity switch and household appliance equipped therewith

A capacitive proximity switch has an electrically conductive sensor surface, which is covered by an electrically non-conductive covering plate and which serves as a part of a capacitor with a capacitance that varies with proximity. The proximity switch includes a reference sensor surface for generating a reference signal for determining an actuation state of the proximity switch. Signal portions of the reference signal are proportional to the capacitance of a reference capacitor formed with the reference sensor surface, and the capacitance of the reference capacitor is determined by surrounding conditions of the sensor surface.