Quick response large current sensor using amorphous MI element resonant multivibrator

A non-contact type small sized large current sensor for inverter controls was constructed utilizing the magnetoimpedance (MI) effect of negative-magnetostrictive amorphous wires (CoSiB) of 5-mm length used as field sensing heads of a resonant type of multivibrator sensor. The sensor head could be set close to a conductor bar by using a negative feedback circuit, which simultaneously improved linearity, dynamic frequency characteristics, temperature stability, temperature variations, and signal-to-noise ratio. Experimental results for detection of DC and AC currents up to 500 A at 25 mm distance (40 Oe) and 2000 A at head angle of 80°C with the cut-off frequency of 300 kHz showed good linearity with less than 0.5% FS non-linearity and temperature stability with less than 0.01%/°C FS variation up to 130°C