Passive MEMS DC Electric Current Sensor: Part I—Theoretical Considerations

This paper, the first of two companion papers, mainly reports theoretical considerations on working principle and structural design of a passive MEMS dc current sensor. The proposed sensor is capable of measuring dc current flowed in a two-wire appliance cord without using any cord separator like that used in Hall-effect based sensor. The crucial component of the proposed sensor is a cantilever made up of a piezoelectric film and a neodymium micro-magnet integrated on the end. The theoretical considerations are emphasized on the effect of partitioning piezoelectric thin film on the total output voltage, the magnetic force acted on the micro-magnet in a magnetic field generated by the dc current, and the cantilever stiffness subject to the sensing principle. A prototype of the proposed MEMS dc current sensor is thus micro-fabricated, with ten PZT partition plates and a 1-mm ³ micro-magnet, in accordance with the theoretical consideration of the design principle. The prototype device provides a physical support for further experimental verifications to be discussed in Part II.