Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review <s> Applications (a) Magnetic Field Sensor <s> Abstract Giant magneto-impedance (GMI) effect has been studied in Fe 73.5 Nb 3 Cu 1 Si 13.5 B 9 glass-covered microwires after heat treatment in vacuum at different temperatures up to 600 °C for 1 h. We present studies on the frequency dependence of the GMI in the range of 1 kHz–10 MHz and the dependence of magnetostriction constant on annealing time. <s> BIB001 </s> Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review <s> Applications (a) Magnetic Field Sensor <s> Abstract Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe 6 Co 94 ) 72.5 Si 12.5 B 15 . 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. <s> BIB002
In work BIB001 it can see a magnetic sensor formed by two parallel microwires. These microwires are connected in series and allows to measure continuous and alternating fields with a sensitivity of 10 mV/(A/m). This sensor was further improved by increasing the range for continuous fields up to 1 kA/m with a compensation coil. Another way we can find in BIB002 a new amplitude detector. It is formed by a device (Direct Digital Synthesizer) connected to a GMI sensor, that produce a voltage which is applied to detector. The output of this detector is proportional to the magnetic field measured and the sensitivity is around 0.0164 V/A/m.