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 pulse-width modulated electrical heater power of a pulse-width modulation frequency and time-varying output signals of the signal generating unit. The signal evaluation unit is configured to monitor a voltage difference between the electrical connection ends of the seat heater member, and is further configured to generate an output signal that is indicative of the seat heater member to be defective, on the basis of a fulfillment of at least one predetermined condition concerning the monitored voltage difference and a phase of the pulse-width modulated electrical heater power.

A vehicle seat occupancy detection system includes at least one capacitive sensor member having at least one sensing electrode, an impedance measurement circuit for determining a complex impedance or a complex admittance of the at least one sensing electrode, an evaluation unit for generating an output signal based on a determined complex admittance of the at least one sensing electrode and comparison of the determined complex admittance to at least one predetermined value, and at least one electrically conductive ground connecting member that is intentionally electrically connected to the reference electrode and that is arranged in close proximity to the at least one sensing electrode. The at least one ground connecting member and the at least one sensing electrode are galvanically separated such that, when the seat gets wet, the sensing electrode is directly electrically connected to the reference electrode by the at least one ground connecting member.

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.

A heater/sensor assembly comprises a sensor assembly and a heater assembly. The sensor assembly comprises a first sheet of an electrically non-conducting material, a first wire attached to a first side of the first sheet, and a second wire arranged parallel to the first wire and attached to a second side of the first sheet that is opposite the first side. The heater assembly comprises a second sheet of the electrically non-conducting material arranged parallel to the first sheet; a third wire attached to a first side of the second sheet facing the second side of the first sheet; and a fourth wire arranged parallel to the third wire and attached to a second side of the second sheet that is opposite the first side of the second sheet. The third and fourth wires are arranged at an angle relative to the first and second wires.

A vehicle seat occupancy detection system includes at least one capacitive sensor member having at least one sensing electrode, an impedance measurement circuit for determining a complex impedance or a complex admittance of the at least one sensing electrode, an evaluation unit for generating an output signal based on a determined complex admittance of the at least one sensing electrode and comparison of the determined complex admittance to at least one predetermined value, and at least one electrically conductive ground connecting member that is intentionally electrically connected to the reference electrode and that is arranged in close proximity to the at least one sensing electrode. The at least one ground connecting member and the at least one sensing electrode are galvanically separated such that, when the seat gets wet, the sensing electrode is directly electrically connected to the reference electrode by the at least one ground connecting member.

Disclosed herein is an occupancy detection device for detecting an occupancy of a seat of a motor vehicle. The occupancy detection device comprises an electric resonant circuit and a sensor element, wherein the electric resonant circuit experiences a change due to a change of the surroundings of the sensor element, so that with reference to the determined electrical parameter an occupancy of the seat can be detected; and a heater control connected with the occupancy detection device such that the sensor element can simultaneously operate as a heater.

A capacitive sensing device includes an antenna electrode for emitting an alternating electric field in response to an alternating voltage caused in the antenna electrode and a control and evaluation circuit configured to maintain the alternating voltage equal to an alternating reference voltage by injecting a current into the antenna electrode and to measure the current. The control and evaluation circuit includes a microcontroller with a digital output for providing a digital signal and a low-pass filter operatively connected to the digital output for generating the alternating reference voltage by low-pass-filtering the digital signal.