Short-Range Detection of Ferromagnetic Target Based on Tunneling Magnetoresistance Sensor

In order to improve the accuracy of short-range ferromagnetic target location and distance-determination, the short-range detection technology of ferromagnetic target based on tunneling magnetoresistance (TMR) sensor is studied in this paper. Based on the analysis of the tunneling magneto-resistance effect principle and the understanding of the relevant magnetic field detecting components, a suitable signal conditioning and signal processing circuit is designed to constitute the TMR magnetic detector. Two kinds of ferromagnetic targets with regular shapes are measured at different distances and orientations, and the measured data are analyzed by curve fitting method. The results show that the output signal amplitude value of the detector is inversely proportional to the cubic power of the relative distance between the detector and the measured target when it is in the near field (no more than 5 meters in this paper). And the influence of the measured target material and detection orientation on the relationship between the two also shows a certain correlation. On the basis of the short-range static detection of general ferromagnetic targets, dynamic tests were carried out with the aim of household cars, the results indicate that the detection distance of dynamic vehicles can reach 7 meters.