Application of Giant Magnetoresistance Sensor for Micro Material Detection

This paper presents the application of giant magnetoresistance (GMR) sensor for micro material detection. The proposed ECT probe was fabricated for detection of conductive microbead by spin-valve type magnetoresistance (SV-GMR). The four exciter coils (Helmholtz, ferrite core, flux concentrator and double spiral) were used to compare the conductive microbead detection of signals that were obtained from GMR sensor. Both of eddy-current testing (ECT) technique and static magnetic methods were applied to detect the ferromagnetic material. In addition, the two GMRs were used to detect the underground water velocity. The results enabled us to determine the position and achieve a good level of signals.