Multi-Threshold Inertial Switch With Acceleration Direction Detection Capability

We present an inertial switch with three threshold levels, which can provide quantitative acceleration measurements and detect the acceleration direction in the x-y plane. The designed device has four movable electrodes attached to the proof mass (one at every side of the square proof mass) and 12 flexible stationary electrodes (three on each side). When the device is subjected to an acceleration input, the movable electrode can contact one or more of the 12 stationary electrodes based on the acceleration magnitude and direction. The acceleration direction can be determined by identifying the individual electrical switches that are activated. The designed switch is simulated using a finite element model under different acceleration signals of various magnitudes and directions. A device prototype has been fabricated using the SOIMUMPs process and has been tested by a drop-table system under various shock accelerations in different directions. The experimental and simulation results show good agreement indicating that the acceleration direction detection accuracy and resolution improve with the increase in the number of used electrical switches.