Patent ID: 8729430

Claim:
Combined seat heater and capacitive occupancy sensor, comprising a heater network including a heating element connected between a first node and a second node to dissipate heat when a heating current is caused to flow between said first and second nodes, a capacitive sensing network connected to said heating element configured to apply an oscillating current thereto and to derive a complex impedance of said heating element from a voltage resulting on said heating element in response to said application of said oscillating current; wherein said heater network comprises a common mode choke connecting said first and said second node to a third and a fourth node, respectively, and wherein said capacitive sensing network comprises means to sustain said oscillating current in or to drive said oscillating current into said heating element; as well as a high-impedance amplifier having an input node operatively connected to said heating element, to probe said voltage, and an output node to provide an output signal indicative of said voltage, said high-impedance amplifier having a complex impedance with a reactive part and a resistive part, the reactive part of the complex impedance of the high-impedance amplifier being at least five times higher than a reactive part of the complex impedance of said heating element and the resistive part of the complex impedance of the high-impedance amplifier being at least five times higher than a resistive part of the complex impedance of said heating element.