Capacitive sensing system configured for using heating element as antenna electrode

摘要

A capacitive sensing system (24) for being connected to a heating element (12) producing heat upon electrical current being caused to flow there across comprises a capacitive detector connectable to the heating element and a common mode choke (28) for connecting the heating element with a heating current supply (22). The capacitive detector is configured for driving an alternating current into the heating element and for producing an output depending on the capacitive load, which the alternating current is subject to. Depending on the object to be sensed, the capacitive load is variable in a range between a minimum value and a maximum value. The common mode choke represents an inductive load in parallel of the capacitive load. The capacitive load and the inductive load contribute together to a complex impedance. The inductive load dominates the capacitive load. A compensation capacitor is arranged in parallel of the choke. The compensation capacitor represents an additional capacitive load also contributing to the complex impedance. The compensation capacitor is dimensioned such that the sum of the additional capacitive load and the maximum value amounts to at least 50 % of the inductive load.