Research On Planar Triaxial Magnetic Sensor Based On Cobalt-based Giant Magneto Impedance Effect

Magnetic sensor based on cobalt-based Giant Magneto Impedance(GMI)effect,due to its high sensitivity,fast response speed,low power consumption,small size,simple excitation mode etc.,has broad application prospects in geological resource exploration,geomagnetic navigation and positioning,nondestructive flaw detection and other fields.The magnitude and direction of the magnetic field can be measured using three perpendicular cobalt-based GMI magnetic sensors.However,when three-dimensional integration of a cobalt-based GMI magnetic sensor,the introduction of a Z-axis magnetic sensor increases the volume of the integrated device.Aiming at this problem,this paper proposes a planar triaxial magnetic sensor based on the cobalt-based GMI effect,which uses the magnetic collector to introduce the Z-axis magnetic field to the XY plane and measure it through the X-axis or Y-axis magnetic sensor.This method avoids the installation of the Z-axis magnetic sensor,so it can not only reduce the volume of the three-axis cobalt-based GMI magnetic sensor,but also reduce the vertical mounting error of the Z-axis magnetic sensor.The main research contents of this paper are as follows:(1)The uniaxial cobalt-based GMI magnetic sensor was prepared and tested.The cobalt-based material was VITROVAC 6025 Z cobalt-based amorphous ribbon produced by VAC,Germany.The material has the advantages of high permeability,low coercivity and nearly zero magnetostrictive coefficient.The cobalt-based amorphous ribbon was 21 mm long,3 mm wide and 0.025 mm thick.The uniaxial cobalt-based GMI magnetic sensor was tested by the vector network analyzer.When the excitation current frequency was 5 MHz,the GMI effect reached 51%.(2)A planar triaxial cobalt-based GMI magnetic sensor was designed.The structure of the device is as followed from top to bottom: annular magnetic collector,cruciform cobalt-based amorphous ribbon and regular octagonal plane bias coil.The bias coil generates a reverse magnetic field on both sides of the cobalt-based amorphous ribbon,in order to improve the linear range and sensitivity of the GMI magnetic sensor.The static magnetic finite element analysis results show that the magnetic fields of the X(Y)axis and Z axis under the action of the magnet collector will produce different distributions on both sides of the cobalt-based amorphous ribbon.Compared with the bias magnetic field direction,the magnetic field of the guided X(Y)axis is in the reverse distribution,while the magnetic field of the guided Z axis is in the same direction.This shows that the X(Y)axis and Z-axis magnetic field signals can be extracted by differential and summation methods.The feasibility of this method has been verified by electromagnetic simulation analysis and magnetic sensor testing in this paper.(3)The cobalt-based GMI magnetic sensor drive circuit was designed.The main modules include: DDS-based signal excitation circuit,Howland-based V-I conversion circuit,preamplifier circuit,phase-sensitive detection circuit based on analog multiplier,and second-order Butterworth low-pass filter circuit and differential amplifier circuit.The theoretical analysis and functional test of the above circuit module are carried out.The results show that the module works normally and meets the design requirements.(4)The testing system for planar three-axis GMI magnetic sensor was established.An automatic testing platform for V-H curve of GMI magnetic sensor is developed by LabVIEW software.The performance of the planar three-axis cobalt-based GMI magnetic sensor was tested.The results show that the sensitivity of the X-axis magnetic sensor is 3.814 V/Oe,the measurement range is-1.6 Oe~+1.6 Oe,the range is 3.2 Oe,the linearity is 1.096% and the background noise is 1.163 nT/?Hz@1Hz;the sensitivity of the Z-axis magnetic sensor is 0.308 V/Oe,the measurement range is-14 Oe ~ +14 Oe,the range is 28 Oe,the linearity is 3.309% and the background noise is 14.396 nT/?Hz@1Hz.