Capacitive detection and/or classification device and operation method for heater member compensation, particularly for automotive application

A capacitive detection device with electric heater member compensation, the capacitive detection device comprising:

• at least one capacitive sensor having at least one electrically conductive sense electrode and at least one electrically conductive auxiliary electrode that are proximal arranged to and mutually insulated from each other, wherein the at least one sense electrode and the at least one auxiliary electrode are arrangeable in the vicinity of an electric heater member,
• a signal voltage source that is configured for providing an alternating measurement voltage with reference to a reference voltage at at least one output port, configured to serve as a measurement signal to be provided to the at least one sense electrode, and a guard signal selectively to be provided to the at least one auxiliary electrode,
• a complex impedance measurement circuit that is electrically connected to the at least one output port, to the at least one sense electrode and to the at least one auxiliary electrode and that is configured for measuring complex sense currents generated in the at least one sense electrode, and for determining a complex impedance based on the measured complex sense current, and is configured to operatively and selectively electrically connect the at least one auxiliary electrode either with the reference voltage or with the guard signal, and
• a control and evaluation unit that is connected to the complex impedance measurement circuit for receiving and evaluating data signals and that is at least configured to control the complex impedance measurement circuit to carry out a complex impedance measurement, for controlling a remotely controllable switching unit for operatively and selectively electrically connecting the at least one auxiliary electrode either with the reference voltage or with the guard signal,
• wherein said control and evaluation unit is further configured for executing at least the following steps:
• provide the measurement signal to the at least one sense electrode and electrically connect the at least one auxiliary electrode to the reference voltage,
• determine a complex electric current flowing through the at least one sense electrode,
• calculate a complex impedance using the determined complex electric current and derive a capacitance value as an emit mode capacitance value,
• electrically disconnect the at least one auxiliary electrode from the reference voltage,
• electrically connect the at least one auxiliary electrode to the guard voltage,
• determine a complex electric current flowing through the at least one sense electrode,
• calculate a complex impedance using the determined complex electric current and derive a capacitance value as a guard mode capacitance value,
• calculate the difference between the guard mode capacitance value and the emit mode capacitance value as a differential loading mode capacitance value, and
• calculate a compensated capacitance value as a weighted sum of the emit mode capacitance value and the differential loading mode capacitance value, wherein the weighting factors are predefined constant values.