DC and AC linear magnetic field sensor based on glass coated amorphous microwires with Giant Magnetoimpedance

• Giant Magneto Impedance phenomenon has been studied in amorphous microwires.
• A combination of two microwires with a bias field has been developed to get a linear response.
• An electronic circuit has been developed to obtain a sensor with a linear response.
• A feedback coil have been added to increase the measurable range of the sensor.

Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe6Co94)72.5Si12.5B15. The impedance of a 1.5 cm length sample has been characterized by using constant AC currents in the range of 400 µA–4 mA at frequencies from 7 to 15 MHz and DC magnetic fields from −900 to 900 A/m. Double peak responses have been obtained, showing GMI ratios up to 107%. A linear magnetic field sensor for DC and AC field has been designed, using two microwires connected in series with a magnetic bias of 400 A/m with opposite direction in each microwire in order to obtain a linear response from ±70 (A/m)rms for AC magnetic field, and ±100 A/m for DC magnetic field. A closed loop feedback circuit has been implemented to extend the linear range to ±1 kA/m for DC magnetic field.