Acceleration sensor unit having self-checking function

摘要

This invention relates to an acceleration sensor system having a self-checking operation of an air bag safety system while a vehicle is being driven. An acceleration sensor element suitable for self-checking while a vehicle is driven is obtained by a planar piezoelectric element supported so that it can vibrate, a detecting electrode provided on an upper face of the planar piezoelectric element, and an actuator to add vibrations at a predetermined frequency to the planar piezoelectric element. A sensitivity checking circuit generates a sensitivity checking signal representing sensitivity of an acceleration sensed from a detected signal. A signal processing circuit generates an acceleration signal representing the applied acceleration to the acceleration sensor from the detected signal. An operation checking circuit generates a self-checking signal representing the operational state of the acceleration sensor system by checking the operation of the signal processing circuit and the acceleration sensor from the acceleration signal and the sensitivity checking signal.