Patent ID: 8138772

Claim:
An occupant sensing system for a seat, comprising: a sensing electrode configured to generate an electric field when power is supplied to the electrode; a shield electrode configured to form a layer parallel to the sensing electrode, the shield layer configured to reduce the electromagnetic influence of electric fields generated by objects located outside of the electric field; and a circuit coupled to the sensing electrode and configured to sense a change in the electric field caused by an occupancy state of the seat, the circuit further configured to ground the shield layer for measuring a first impedance at the sensing electrode, to ground the sensing electrode for measuring a second impedance at the shield layer, to electrically couple the sensing electrode and shield electrode together for measuring a third impedance at the sensing electrode and shield electrode, and to determine the impedance from the sensing electrode to ground based on the first, second, and third impedances, wherein the determined impedance from the sensing electrode to ground does not include an impedance from the sensing electrode to the shield layer.