Patent ID: 7271730

Claim:
An occupant determination apparatus comprising: a first sensor section having a plurality of seat section electrodes arranged on a seating section of a seat having the seating section on which an occupant sits and a backrest section; and a first determination section which detects each capacitance formed between the seat section electrodes by using a predetermined first signal for capacitance measurement, in order to determine a size of the occupant, wherein the first sensor section has a reference electrode array where a plurality of reference candidate electrodes, included in the plurality of the seat section electrodes, are arranged by a predetermined rule, the first determination section comprises: an electric field generating device which outputs the first signal; a capacitance measuring device which detects each capacitance between the seat section electrodes based on a current flowing through each of the seat section electrodes corresponding to the first signal; a switching device which sequentially switches a connection of the capacitance measuring device to the plurality of the seat section electrodes based on a switch control signal; and a controlling device which outputs the switch control signal, and the controlling device comprises: a selecting device which sets one of the reference candidate electrodes included in the reference electrode array as a reference electrode, based on measurement capacitances of the seat section electrodes determined by detection capacitances of each of the seat section electrodes which are detected by the capacitance measuring device; a first calculating device which determines the size of the occupant based on a distance between the reference electrode and the occupant which is calculated from the measurement capacitance and an area of the reference electrode, and the measurement capacitances of the seat section electrodes included in the first sensor section; and a switch signal generating device which outputs the switch control signal.