US Patent 7436299 Vehicle occupant detection using relative impedance measurements

A passenger detection system is provided. A sensor measures capacitance, electric field effects or other characteristic responsive to a load in a seating area. The sensor uses one or more electrodes (e.g., a transmit and receive electrode or one electrode for transmit and one or more electrodes for receive). Other electrodes are connected with different impedances. Measuring by a sensor, but with other electrodes connected with different impedances, may distinguish between an occupant and inanimate objects, may distinguish between characteristics of a passenger (e.g., size, height, weight or position), or may indicate a grounding state of an occupant.