Bistable Current Sensing Scheme Applicable to Two-Wire DC Appliances

Abstract

This paper proposes a bistable cantilever-based current sensing scheme for measuring dc current flow in a two-wire appliance cord constantly without using a cord separator to realize wide measurement range and high sensitivity without extra component from the typical cantilever-based oscillating type dc sensing system. Bistability has been introduced into dc current sensing system for the first time simply by changing the positions of magnet pole and current core. Through theoretical analysis and analytical studies, we find that as the applied dc current increases, the bistable sensing system also exhibits interwell oscillations and intrawell oscillations as the bistable energy harvester. It is proved that the output displacement amplitude is approximately proportional to the applied dc current in the interwell oscillations area where the vibrational trajectory is symmetric and the output displacement amplitude is dramatically improved. Therefore, on the same conditions the measurement range of the proposed work is 11 times wider than the oscillating type and the sensitivity is over 2 times higher than the oscillating one. In addition, we find that as interval decreases or magnet’s volume increases, the sensitivity increases accordingly while the maximum range determined by interwell oscillations area decreases. The differential equation of the proposed system is further analyzed to predict the relative output displacement. The method proposed here could shed light on bistable current sensing scheme and might be applied to self-powered current sensing system in vibrational environment.