A passive AC/DC current sensing methodology for diverse multiline cables

Abstract

A photoelectric cantilever-based current sensing methodology, mainly composed of a cantilever, a magnet, an analyzer, and a photodiode, for passive measuring diverse multiline cables with diverse currents, is proposed for the desirable application of a Wireless Sensor Node (WSN) in Internet of Things (IoT). The basic idea is to achieve a synchronous vibration of both the analyzer and the cantilever to modulate the natural light signal incident on the photodiode. In this Letter, the magnet, fixed at the end of the cantilever, is used to passively convert the applied current induced magnetic force into a cantilever vibration, which is further converted to a polarization angle variation via the above synchronous vibration. The natural light signal is accordingly modulated and a varied voltage, as a function of the applied current, is thus output from the photodiode. A two-wire DC electric current is used to verify the validity of the sensing mechanism. The measurement error can be decreased to less than half of the theoretical one by calibration, and the linear range can be further adjusted by changing a value on the host computer. Compared to the piezoelectric cantilever-based one, the proposed photoelectric cantilever-based methodology can achieve a continuous measurement of DC and its variation with a higher resolution, and both a faster response and a higher resolution for AC, and thus is more suitable for IoT applications.