Development of differential probes in pulsed eddy current testing for noise suppression

Differential probes are developed to suppress noises and improve the sensitivity and robustness of pulsed eddy current (PEC) testing. As the close magnetic circuit is used to concentrate the magnetic field, three-core probe and U-shape probe gain high signal to noise ratio (SNR) with limited excitation current, the latter also reduces the influence caused by probe tilting. Lift-off effect is a great obstacle for practical application of pulsed eddy current testing, so probes developed with two-stage differential design can carry out the effective suppression of the lift-off effect. Verifying experiments are also presented, by which the performance of these differential probes are tested and compared in this paper.