Theoretical and experimental study on novel weak current sensor using single nanocrystalline toroidal core with double-winding

Abstract

Fe 73.5Cu 1Nb 3Si 13.5B 9 nanocrystalline core made by furnace annealing under nitrogen atmosphere can show good thermal stability of magnetic properties and excellent soft magnetic properties. Based on the characteristic of the sensitive magnetic core, we proposed a novel non-contact weak current sensor adopting single nanocrystalline core with double-winding excited by a multivibrator bridge. The measurement principle based on an established mathematic model for the sensor was described in details. The observed phenomenon is consistent with the theoretical results and the model, indicating that the key factors affecting the performance of the sensor includes the magnetic parameters of the sensing materials, the number of turns of the coils and circuit parameters in the multivibrator bridge. In other words, we can design sensor freely to meet different requirements according to its theory. The output signal of the multivibrator bridge was analyzed by Fourier transform. Moreover, the method to design the corresponding signal conditioning circuit was presented. The zero drift of the sensor was maintained within 0.01%FS at 25 °C for 2 h, and the temperature offset drift for zero input current was less than 0.03%FS/°C for temperature variation from −15 °C to 50 °C.