CAPACITIVE OCCUPANCY OR PROXIMITY DETECTOR

A capacitive occupancy or proximity detector includes a heating circuit, an impedance measurement circuit connected to the heating element and a diagnostic circuit configured for determining integrity of the heater element. The heating circuit includes a heating element, a heating current source and a common mode choke having a first and a second winding, the heating element being connectable to the heating current source via the first and second windings. The diagnostic circuit includes at least one controllable switching element coupled across the second winding circuitry for injecting a DC current into a series connection formed by the first winding, the heating element and a parallel connection of the second winding and said at least one controllable switching element; and at least one detection circuit for detecting a voltage variation across the second winding.