Noninvasive Passive Measurement of Multiphase Currents in IoT

The feasibility and the diversity of cantilever-based current sensing mechanism, which mainly comprised a cantilever with a permanent magnet on its free end, are verified for desirable applications of wireless sensor network (WSN) in Internet of Things (IoT). In the noninvasive multiphase current measurement, the applied current induced magnetic force is passively converted into a cantilever vibration via the magnet. The cantilever vibration can be further converted to an output voltage as a function of the applied current via diverse detecting units, enabling the diversity of cantilever-based current sensing mechanisms. In this article, cantilever-based methodology is verified to be applicable to multiphase current measurements, with considering decoupling and reconstructing in case of unbalanced ones. As a typical demonstration, three-phase four-wire ac current is passively measured via the positive piezoelectric effect of the piezoelectric detecting unit. Since the measurement of current is physically the noninvasive passive measurement of the gradient of the superimposed magnetic field, the cantilever-based current sensing methodology is applicable to a wide range of diverse current measurements of WSN in various IoT use cases.