The Giant Magneto-impedance Effect In The Application Of Current Sensor Research

The giant magneto-impedance(GMI) effects is a newly kind of magnetic effect,with high sensitivity,fast response,non-contact,wide frequency of use and small sensitive element size.It offers a new facility for developing a current sensor.In this thesis,the GMI effect theory and the GMI effect in Co66Fe4Ni1Si15B14amorphous ribbon have been investigated systematically.A novel non-contact GMI current sensor is designed.The main contents are generalized as follows:The high-frequency GMI effect of the ribbon with a nearly transverse magnetic domain structure is proposed.The expression of impedance and effective permeability have been deduced by solving Maxwell equation and Landau-Lifshitz equation with the damping term.The impact of the dynamic part of induced magnetic anisotropy and equivalent stess field have been considered.Moreover,the related magnetic parameters and measurements on GMI effct are analysised.The GMI effect of Co66Fe4Ni1Si15B14amorphous ribbon sputtered CoFe2O4film are studied.The experimental results show that CoFe2O4film can effectively improve the surface roughness of Co-based amorphous ribbon and improve the GMI ratio.Comparing with the casted sample of the maximum GMI ratio39.4%,the deposited sample of the maximum GMI ratio58.9%is increased by19.5%under the optimum sputtering condition of power:100W,time:30min,Ar pressure:0.9Pa.As the length of the sample increase,the GMI effect enhances accordingly. When the length is longer than50mm,the GMI effect tends to saturation.In this thesis, the influence of isothermal annealing and DC Joule heating treatment on GMI effect in material have been investigated systematically.The optimal procedure parameters of isothemal annealing are annealing temperature:300℃,annealing time:60min,and the highest GMI ratio is96.9%when excitation frequency is1MHz.Accordingly,the optimal procedure parameters of DC Joule heating are annealing current density:30A/mm2,annealing time:120s,and the highest GMI ratio is115.2%when excitation frequency is1MHz.A novel non-contact GMI current sensor is designed.The sensor circuit consists of signal circuit, preamplifier circuit, low-pass filter, peak detector circuit and differential amplifier circuit.The test results show that a novel GMI current sensor with a measurement range of0～2.4A,the sensitivity of1.08V/A,the linearity of±2.09%FS,the hysteresis of0.31%FS and the precision of±2.11%FS.