Leakage flux testing using a GMR line sensor and a rotating magnetic field

A new system configuration of magnetic leakage flux testing using a GMR line sensor and a rotating magnetic field is proposed. The GMR line sensor, which we developed, can visualize a magnetic field distribution by a single axis scan. Directional sensitivity and frequency characteristics of the multilayer GMR element are shown. Leakage flux is generated near a defect. Using a rotating magnetic field, the leakage flux can be generated independent of the direction of the defect. Using this system, leakage flux distribution near the defect is detected and it is shown that the shape of defect is identified.