Patent ID: 8405408

Claim:
A capacitive occupant detecting apparatus comprising: a voltage applying portion configured to generate an alternating-current voltage signal; a capacitance sensor including an electrode disposed in a seat of a vehicle, the capacitance sensor configured to output an electric current in accordance with a change in an electric field generated between the electrode and a vehicle body when the alternating-current voltage signal is applied to the electrode, the vehicle body coupled with a vehicle grounded portion; a line coupling the voltage applying portion and the capacitance sensor; a capacitor coupled with the line so as to be applied with the alternating-current voltage signal; a storing portion configured to store a reference voltage; a measuring portion configured to detect a first voltage in accordance with an electric current that flows between the voltage applying portion and the capacitor when the alternating-current voltage signal is applied to the capacitor, the measuring portion configured to detect a second voltage in accordance with the electric current output from the capacitance sensor when the alternating-current voltage is applied to the capacitance sensor; and a calculating portion configured to detect an abnormality of the voltage applying portion based on the first voltage and the reference voltage, the calculating portion configured to determine an object disposed on the seat based on the second voltage; a first switch disposed on the line coupling the voltage applying portion and the capacitance sensor; and a second switch disposed on another line coupling the voltage applying portion and the capacitor; wherein when the first voltage is different from the reference voltage, the calculating portion determines that a frequency of the alternating-current voltage signal is abnormal; and the capacitor is applied with the alternating-current voltage signal when the first switch is turned off and the second switch is turned on.