Current sensor utilizing giant magneto-impedance effect in amorphous ribbon toroidal core and CMOS inverter multivibrator

The giant magneto-impedance (GMI) effect was observed in almost zero-magnetostrictive Co66.3Fe3.7Si12B18 amorphous ribbon toroidal cores after annealed by a 25 A/mm2 pulse current density under a transverse magnetic field of 2 kA/m for 30 s. A maximum GMI ratio of 34% and a sensitivity of about 65%/Oe were measured employing a 900 kHz sharp pulse current generated by a CMOS inverter multivibrator. A sensitive non-contact type current sensor composed of an amorphous ribbon toroidal core connected with a pulse current generator, a peak detector, and a differential amplifier is presented. The sensor is able to examine the value and direction of dc current. The measurement accuracy of 0.45% and sensitivity of 0.67 V/A were obtained with full scale ±2.5 A using a power source voltage of 5 V.