Research On Metal Detector Based On Magnetoresistance Sensor Array

Metal detector is an electronic equipment used to detect metal objects.This paper mainly studies the metal detection equipment used to detect metal impurities in assembly line materials.Rectangular transmitting coil and TMR sensor array are used as detection probes to replace the traditional transceiver coil,which has the advantages of small size,low power consumption and high precision.This article adopts active magnetic detection technology based on magnetization effect and eddy current effect,which can simultaneously detect ferromagnetic metals and nonferromagnetic metals.According to the established theoretical model of metal detection,the background magnetic field of the rectangular excitation coil and the secondary induction field of the metal target are analyzed,and then the finite element simulation model of metal detection is established to analyze the magnetic field characteristics of different materials of metal.By studying the influence of the detection distance and excitation frequency on the magnetic field of the target,the detection distance and the excitation frequency of the different types of materials are determined.In turn,a metal detection system is designed with dual-frequency excitation.In order to avoid the interference of electromagnetic noise in detection,a matched filtering algorithm based on the magnetic anomaly signal of metal target is proposed to extract the target signal,which can greatly improve the detection ability of the system.Based on the matched filtering amplitude of the signal,a grid search method is proposed to locate the target,which is convenient for the subsequent system to eliminate the impurity target.On the basis of technical principle of active magnetic detection,the software and hardware modules such as excitation signal box,probe device and data acquisition device are designed.Finally,a dual frequency metal detection system is developed to detect and locate metal particles.The experimental results show that the system has good detection effect and positioning accuracy.