A Pulsed Eddy Current Testing Sensor Made of Low-Cost Off-the-Shelf Components: Overview and Application to Pseudo-Noise Excitation

A low-cost device for eddy current non-destructive testing made of off-the-shelf components is described. The system consists of a dual H-bridge stepper motor driver, a coil wound in-house on an additively manufactured support, a tunneling magnetoresistance sensor, and a data generation/acquisition module. The system is compact, and it can flexibly generate rectangular pulses, square wave bursts and arbitrary binary excitation waveforms. Among these, in this paper pseudo-noise binary signals were used within a pulse-compression measurement protocol to increase the SNR and the inspection sensitivity with respect to pulsed excitation. A benchmark sample was analyzed, and all the defects were correctly located, demonstrating a good detection capability of the overall hardware-software solution proposed. It was also found that pulse-compression output signals can be further processed as standard pulsed eddy current data. Features can be extracted from them for defect classification purposes and the lift-off invariant point can be used for imaging. These results were achieved by assembling a low-cost handy device, which can be further improved in portability and performances using different off-the-shelf components and by integrating it with a single-board PC, paving the way for future developments in this field.