Planar Eddy Current Sensor Array With Null-Offset

Aiming at the problem of low resolution of traditional eddy current sensor for buried defects detection in metal materials, a null-offset planar eddy current sensor array is designed, realized, and tested. The arrayed sensor is composed of a spatially periodic excitation coil and multiple differential detection coils, which are skillfully designed and can effectively suppress the common mode component in the induced voltage and improve the signal-noise-ratio of the sensor. The null-offset eddy current sensor is fabricated and utilized to detect the buried defects 0.5-mm depth beneath the surface of aluminum alloy test pieces. The simulation and experimental results show that the null-offset eddy current detection unit improves the detection resolution of buried defects by more than 1000 times.