Optimizing Surface Type Eddy Current Probe Design with Dual Induction for Wobble Noise Suppression

In eddy current testing, probe lift-off and probe wobble noise is detected, as well as the flaw signal, and the noise is often larger than the flaw signal. In order to suppress this noise, signal processing and probe design have been devised. In this paper, surface eddy current probe with dual induction is proposed and its noise suppression effect is explained using numerical analysis and experimental results. The novelty lies in the application of the dual induction method to surface eddy current probe and the use of phase shifters during the optimal design of the coil geometry. The paper begins with a numerical analysis that shows the effect of the dual induction method on the noise suppression of the probe, which has not been observed in the encircling probe. The paper first confirms the characteristic of the phase shifter, and clarifies the necessity of the phase shifter since the phase is not 180° symmetrical when the intensity ratio becomes the most constant. The optimal design obtained by numerical analysis was used to make a probe, and it was clarified that the optimal design showed a suppression effect of up to 94% in actual measurements.