Abstract: An impedance measurement circuit for determining a complex impedance of a capacitive sensor having at least one sense electrode operable in loading mode and at least one guard electrode. The measurement circuit includes: a pulse generator unit for providing a periodic electric measurement signal and a periodic electric guard signal; a signal sensing circuit for sensing a sense current flowing through the at least one sense electrode or the sense electrodes in response to the pulse generator unit measurement signal; and a control and evaluation unit. The control and evaluation unit is configured for determining a complex impedance from the determined sense currents with reference to a complex reference potential.

Abstract: A method of operating a capacitive sensing device that includes a capacitive sensor having at least one sense electrode, a measurement signal source for providing an alternating electric measurement signal with at least three fixed predefined signal frequencies to the at least one sense electrode, and an impedance measurement circuit for determining an unknown complex impedance of the at least one sense electrode from a response to the provided electric measurement signal.

Abstract: An impedance measurement circuit for determining a complex impedance of a capacitive sensor having at least one sense electrode operable in loading mode and at least one guard electrode. The measurement circuit includes: a pulse generator unit for providing a periodic electric measurement signal and a periodic electric guard signal; a signal sensing circuit for sensing a sense current flowing through the at least one sense electrode or the sense electrodes in response to the pulse generator unit measurement signal; and a control and evaluation unit. The control and evaluation unit is configured for determining a complex impedance from the determined sense currents with reference to a complex reference potential.

Abstract: A method of operating a capacitive sensing device that includes a capacitive sensor having at least one sense electrode, a measurement signal source for providing an alternating electric measurement signal with at least three fixed predefined signal frequencies to the at least one sense electrode, and an impedance measurement circuit for determining an unknown complex impedance of the at least one sense electrode from a response to the provided electric measurement signal.

Abstract: A capacitive sensor arrangement includes a sensing electrode having a capacitance (Cx) which depends on the presence of an object in a detection space; a measurement device connected to the sensing electrode and configured to detect the capacitance (Cx) of the sensing electrode; and a conducting structure, wherein the capacitance (Cx) of the sensing electrode depends on a potential of the conducting structure. In order to obtain a reliable capacitive measurement, the measurement device is connected to a power supply between a first potential (Vs) and a second potential (GND), the measurement device being connected to the second potential exclusively via the structure.

Abstract: A method of operating a capacitive sensing device for diagnosing a galvanic connection of at least one guard electrode. The capacitive sensing device includes at least one sense-guard capacitive sensor and a capacitive measurement circuit. The sense-guard capacitive sensor includes a first electrically conductive sense electrode and a first electrically conductive guard electrode and at least a second electrically conductive sense electrode, which is galvanically separated from the first sense electrode, and at least a second electrically conductive guard electrode. Each of the guard electrodes is proximally arranged to at least one of the sense electrodes and is galvanically separated from each of the sense electrodes. The method uses a calculated difference of imaginary parts of complex sense currents resulting from coupling mode measurements between at least two of the sense electrodes for assessing a status of the galvanic connection of the guard electrodes.

Abstract: A sensor arrangement for capacitive position detection of a hand on a steering wheel. The sensor arrangement includes: a plurality of capacitive sensors disposed along a detection surface, which is an outer surface of the steering wheel, each sensor having at least one sensor electrode; and a measurement device electrically connected to the sensors. In order to increase the reliability of capacitive hand detection on a steering wheel, the measurement device is adapted to perform a sequence of detection operations, and in each detection operation, to activate at least one sensor by applying a detection signal to its at least one sensor electrode in order to capacitively detect the hand while grounding at least one other sensor by connecting at least one of its sensor electrodes to ground, and to activate different sensors in consecutive detection operations.

Abstract: A sensor arrangement for capacitive position detection of a hand on a steering wheel. The sensor arrangement includes: a plurality of capacitive sensors disposed along a detection surface, which is an outer surface of the steering wheel, each sensor having at least one sensor electrode; and a measurement device electrically connected to the sensors. In order to increase the reliability of capacitive hand detection on a steering wheel, the measurement device is adapted to perform a sequence of detection operations, and in each detection operation, to activate at least one sensor by applying a detection signal to its at least one sensor electrode in order to capacitively detect the hand while grounding at least one other sensor by connecting at least one of its sensor electrodes to ground, and to activate different sensors in consecutive detection operations.

Abstract: A method of operating a capacitive sensing device for diagnosing a galvanic connection of at least one guard electrode. The capacitive sensing device includes at least one sense-guard capacitive sensor and a capacitive measurement circuit. The sense-guard capacitive sensor includes a first electrically conductive sense electrode and a first electrically conductive guard electrode and at least a second electrically conductive sense electrode, which is galvanically separated from the first sense electrode, and at least a second electrically conductive guard electrode. Each of the guard electrodes is proximally arranged to at least one of the sense electrodes and is galvanically separated from each of the sense electrodes. The method uses a calculated difference of imaginary parts of complex sense currents resulting from coupling mode measurements between at least two of the sense electrodes for assessing a status of the galvanic connection of the guard electrodes.

Abstract: A capacitive sensor arrangement includes: a sensing electrode having a capacitance (CX) which depends on the presence of an object in a detection space; a measurement device connected to the sensing electrode and configured to detect the capacitance (CX) of the sensing electrode; and a conducting structure, wherein the capacitance (CX) of the sensing electrode depends on a potential of the conducting structure. In order to obtain a reliable capacitive measurement, the measurement device is connected to a power supply between a first potential (VS) and a second potential (GND), the measurement device being connected to the second potential exclusively via the structure.

Abstract: A capacitive vehicle seat occupancy detection and classification system includes an impedance measurement circuit and a control and evaluation unit. The impedance measurement circuit is configured for providing periodic electrical measurement signals to a capacitive sensor of N different fundamental frequencies, wherein N is a natural number of at least 3, and to determine a complex impedance from each of determined sense currents in the capacitive sensor. The control and evaluation unit is configured to determine a seat occupancy class for each one of the complex impedances determined at the at least N different fundamental frequencies, and to determine a final seat occupancy class derived by a majority decision among the determined seat occupancy classes.

Abstract: A capacitive detection system for detecting occupancy of a vehicle seat includes a signal generating unit and a signal evaluation unit. The vehicle seat has a seat heater member configured for receiving time-varying output signals of the signal generating unit. The signal evaluation unit is configured to generate an output signal that is indicative of the seat heater member to be defective, if the sensed capacitance of the seat heater member is less than a second predetermined threshold value for the sensed capacitance.

Abstract: A capacitive occupancy or proximity detector includes a heating circuit, an impedance measurement circuit connected to the heating element, and a diagnostic circuit configured for determining integrity of the heater element. The heating circuit includes a heating element, a heating current source and a common mode choke having a first and a second winding, the heating element being connectable to the heating current source via the first and second windings. The diagnostic circuit includes at least one controllable switching element coupled across the second winding, circuitry for injecting a DC current into a series connection formed by the first winding the heating element and a parallel connection of the second winding and the at least one controllable switching element, and at least one detection circuit for detecting a voltage variation across the second winding.

Abstract: A capacitive occupancy or proximity detector includes a heating circuit, an impedance measurement circuit connected to the heating element and a diagnostic circuit configured for determining integrity of the heater element. The heating circuit includes a heating element, a heating current source and a common mode choke having a first and a second winding, the heating element being connectable to the heating current source via the first and second windings. The diagnostic circuit includes at least one controllable switching element coupled across the second winding circuitry for injecting a DC current into a series connection formed by the first winding, the heating element and a parallel connection of the second winding and said at least one controllable switching element; and at least one detection circuit for detecting a voltage variation across the second winding.

Abstract: A capacitive detection system for detecting occupancy of a vehicle seat includes a signal generating unit and a signal evaluation unit. The vehicle seat has a seat heater member configured for receiving time-varying output signals of the signal generating unit. The signal evaluation unit is configured to generate an output signal that is indicative of the seat heater member to be defective, if the sensed capacitance of the seat heater member is less than a second predetermined threshold value for the sensed capacitance.