Spatial detection of ferromagnetic wires using GMR sensor and based on shape induced anisotropy

The purpose of this paper is to introduce a new technique for row spacing measurement in a wire array using giant magnetoresistive (GMR) sensor. The self-rectifying property of the GMR-based probes leads to accurately detection of the magnetic field fluctuations caused by surface-breaking cracks in conductive materials, shape-induced magnetic anisotropy, etc. The ability to manufacture probes having small dimensions and high sensitivity (11 mV/mT) to low magnetic fields over a broad frequency range (from dc up to 1 MHz) enhances the spatial resolution of such a probe that is applicable to eddy current testing (ECT) techniques. Here, an AC uniform magnetic field is formed using a Helmholtz coil in which by scanning the probe over an array of acupuncture needles, the distances between them are detected. The results verified the possibility and the performance of the proposed row spacing measurement using GMR sensor.