Detection of Metal Surface and Back Surface by Rectangular Wave Eddy Current Testing with Magneto Resistive Sensor

Eddy current testing (ECT) at different frequencies can identify surface and back-surface defects caused by the skin effect. Therefore, we present the development of a rectangular wave eddy current testing (RECT) system using a magneto resistive (MR) sensor. The system uses rectangular wave excitation, which can generate both low and high frequency signals, and an MR sensor to detect the magnetic field components. A 12-mm thick aluminum plate with an artificial circular defect of 10 mm in diameter and 6 mm in depth was used as a specimen. The measurement results reveal that the developed system can effectively and quickly distinguish between surface and back-surface defects.