An innovative eddy Current sensor with E-Core ferrite resistant to lift-off and tilt effects

Abstract

ABSTRACT The detection of defects can be seriously affected by lift-off and tilt effects, which represents significant challenges for eddy current testing (ECT). In this paper, an innovative eddy current sensor with E-core ferrite is proposed to overcome these challenges. The sensor comprises two excitation coils, one receiving coil, and an E-shaped ferrite core. The excitation coils and receiving coil are wound on two sides and the middle of the E-core, respectively. Specially, the two excitation coils are wound in opposite directions, resulting in magnetic field cancellation in the middle receiving coil when there is no defect in the plate. All the design principle, simulation, and experimental verification demonstrate the feasibility and excellent performance of the proposed sensor. Moreover, the proposed sensor can assess the depth of defects and achieve defect localisation based on the proposed measurement method. The results indicate that the defect depth can be accurately classified and identified based on the measured signal amplitude. The localisation of defects on aluminium sheets shows excellent results for depths ranging from 0.6 mm to 2.0 mm. However, for stainless-steel sheets, the defect localisation results show an unexpected error rate of over 15% when the defect depth is less than 1.1 mm.