Latching ultra-low power MEMS shock sensors for acceleration monitoring

A microelectromechanical shock sensor, which uses a latching mechanism to record a shock event above a specified threshold level, is discussed in this article. The fabrication process for the shock sensor, which includes wafer-level vacuum packaging, is detailed along with the design features. These features include a reset actuator for reuse of the sensor, a no-power operation scheme when the reset actuator is not activated, and a control circuit to minimize power used to unlatch the sensor. In order to describe the shock-sensor dynamics and interaction with the latch mechanism, a preliminary non-linear model has been developed. Experimental results are presented and compared with model predictions.