Electrical circuit configuration for alternating heating and capacitive measuring operation with functional testing and associated method and use

An electrical circuit configuration for an alternating heating and a capacitive measuring operation, comprising:

• a pair of first switching elements and a pair of second switching elements;
• a heating wire, which is connected to the pair of first switching elements and the pair of second switching elements in such a way that, in a heating operation during which the pair of first switching elements and the pair of second switching elements are in a conducting state, the pair of first switching elements and the pair of second switching elements and the heating wire are connected in series, and the heating wire is conductively connected to one of two different heating potentials via one of the pair of first switching elements and one of the pair of second switching elements connected to the pair of first switching elements via a conductor section, such that a heating current is applied to the heating wire;
• a detection circuit configured to determine a measuring capacitance of the heating wire with respect to a reference potential by applying an AC voltage of an AC voltage source to the heating wire in a measuring operation falling outside a time frame of the heating operation;
• a test circuit including at least one third switching element and a test impedance;
• a control circuit adapted to switch the pair of first switching elements and the pair of second switching elements from the heating operation to the measuring operation, wherein, during the measuring operation, the pair of first switching elements and the pair of second switching elements are in a blocking state, such that the two connections of the heating wire that are electrically conducting in the heating operation at the two different heating potentials are each interrupted multiple times in the measuring operation and the control circuit is further adapted to switch the test circuit in a test phase falling within the measuring operation in such a way that the test impedance is added to the measuring capacitance, and an associated change in the measuring capacitance and/or a total impedance made up of the measuring capacitance and the test impedance is at least detected by the detection circuit.