Developing MEMS Electric Current Sensors for End-use Monitoring of Power Supply: Part IX - Threshold-Triggered Current Sensing

A passive type MEMS DC current sensor for monitoring the electricity consumption by either one-wire or two-wire appliance cord was proposed, micro-fabricated and tested in our past work (DTIP 2011, 2012). A novel oscillating type MEMS DC current sensor, comprised of both actuating and sensing elements, was further proposed for constant DC current measurement (DTIP2013). The relationship between magnetic induction and sensitivity of the DC current sensor was discussed both analytically and experimentally (DTIP2017). In this work, exploratory study on threshold-triggered AC current sensing mechanism by making use of bistability applicable to two-wire AC appliances is proposed in this work. It can monitor the AC current whether reaches a critical level when it is used for AC current. Only when the monitored amplitude of AC current reaches a preset threshold, the bistable piezoelectric cantilever sensing system will transform from intrawell oscillations to interwell oscillations, realize snap-through and give out a high output.