Patent ID: 7679378

Claim:
A dual function capacitive sensor apparatus for detecting an occupant of a seat, the seat including a foam cushion supported on a frame and covered with a seat cover, the sensor apparatus comprising: a capacitive load cell disposed between the foam cushion and the frame, including upper and lower conductive plates biased apart by a resilient member that compresses to reduce a separation distance between said conductive plates in response to force applied to the seat by the occupant; an electric field emitter disposed between the foam cushion and the seat cover in a seating area of said seat; a capacitance-responsive control circuit coupled to both the capacitive load cell and the electric field emitter for determining (1) a seated weight of the occupant based on a first capacitance between said upper and lower conductive plates, and (2) an electric field coupling of the occupant based on a second capacitance between the electric field emitter and a ground reference; and a control unit coupled to the capacitance-responsive control circuit for detecting the occupant based on the determined seated weight and the determined electric field coupling; wherein said electric field emitter includes an insulative mat, a first conductor disposed on an upper surface of said insulative mat adjacent said seat cover, and a second conductor disposed on a lower surface of said insulative mat adjacent said foam cushion: and said control circuit applies substantially identical AC signals to the first and second conductors.