Patent ID: 8378819

Claim:
An electrostatic occupant detection apparatus comprising: an electrostatic sensor including a main electrode, which is located in a vehicle seat, and a guard electrode, which is located between a vehicle body and the main electrode and spaced from the vehicle body and the main electrode, the vehicle body being conductive with a vehicle grounded portion; a sensor-characteristics detection unit configured to: selectively apply an alternating voltage signal to each of the main electrode and the guard electrode of the electrostatic sensor; selectively cause each of the main electrode and the guard electrode to be opened or grounded; cause, in these conditions, a selection unit to select a potential difference between ends of one of resistors connected to the main electrode and the guard electrode respectively; cause a current conversion unit to convert the selected potential difference into an electric current; cause a voltage conversion unit to convert the electric current into a voltage value; and cause an overcurrent detection unit separately to detect an overcurrent in each of the main electrode and the guard electrode when the alternating voltage signal is applied; and an arithmetic control unit configured to, according to one or a combination of the voltage value detected by the sensor-characteristics detection unit and detection or non-detection of the overcurrent by the sensor-characteristics detection unit: determine whether an open failure occurs in each of the main electrode and the guard electrode; determine whether a power supply short failure occurs due to a short-circuit between a connection path from a power supply to a signal source, which is for applying the alternating voltage signal to each of the main electrode and the guard electrode, and another electric conduction element; determine whether a grounded failure occurs in each of the main electrode and the guard electrode; and determine whether a short failure occurs between the main electrode and the guard electrode.