Designing GMR Sensor Probe Using Transmitter Coil for Artificial Crack Identification on Brass and Mild Steel Calibration Block

Giant Magnetoresistance (GMR) sensors have become increasingly popular for Non-Destructive Testing (NDT) applications, especially in eddy current inspection. GMR sensors have high sensitivity and low noise characteristics, and they have been used for detecting surface cracks in conductive materials and monitoring the structural health of steel bridge cables. According to the GMR sensor application, it also can be used for detecting corrosion on pipelines compared to conventional eddy current systems that are only applicable to measure the coating thickness and depth of defect on pipeline. In this work, the designing of a GMR sensor probe by using coil as the excitation signal transmitter has been done for measuring the depth of defect based on a calibration block on two types of material within brass and mild steel material. This system will measure the lower depth is 0.5 mm and the higher depth 5 mm. The turn of coil for the excitation signal transmitter is set on 600turns where the diameter of the coil is 0.17 mm. Based on the Brass steel calibration block, a sudden increase occurs at a defect depth of 5 mm which is as much as 2.443Vp compared to the previous one which is 2.427Vp (4.5 mm) and 2.421Vp (4 mm). In addition, a sudden increase also occurred for mild steel, which is in the defect depth of 3.5 mm, which is 2.458Vp compared to the previous 2.441Vp (3 mm) and 2.431Vp (2.5 mm). Finally, the result shows that when the depth of defect is increased then the value of signal Voltage peak (Vp) also increases.