Abstract: A circuit for measuring a complex alternating current resistance comprises a signal source which is designed to generate an alternating voltage excitation signal, a first signal path, a second signal path and a third signal path, into each of which the alternating voltage excitation signal of the signal source is fed in parallel to one another. The alternating voltage excitation signal is fed into the first signal path or into the second and third signal path at least temporarily with a phase offset compared to the alternating voltage excitation signal generated by the signal source. The first signal path has a high-pass filter and, in series therewith, the alternating current resistance to be measured. A measurement signal tapped at a measuring point between the high-pass filter and the alternating current resistance to be measured is mixed with the alternating voltage excitation signal in the second signal path and furthermore demodulated in order to obtain a first demodulated measurement signal.

Abstract: A capacitive sensor including a sensor electrode connected to a signal generation circuit and a signal evaluation circuit. The signal generation circuit contains a signal generator that is a noise generator or a pseudo-noise generator, the signal evaluation circuit includes a synchronous rectifier. The synchronous rectifier is connected for synchronization to the signal generator.

Abstract: A capacitive sensor including a sensor electrode connected to a signal generation circuit and a signal evaluation circuit. The signal generation circuit contains a signal generator that is a noise generator or a pseudo-noise generator, the signal evaluation circuit includes a synchronous rectifier. The synchronous rectifier is connected for synchronization to the signal generator.