Extraction of crack indications from ECT signals using signal phase characteristics of a multi-coil probe

This paper proposes a method to reduce noise and extract crack indications from detection signals of a 48-channel ECT system based on its signal phase characteristics. Because this 48-channel ECT system performs two kinds of scanning patterns: U-scan and T-scan, and obtains two sets of signal distributions for one scanning area simultaneously, the proposed method uses a two-stage process that includes so-called main filter and sub filter. Using these two filters imposes more strict conditions on extracting crack indications so as to reduce more noise. The experimental results show that the proposed filtering method is effective to extract only crack indications from detection signals including complicated noises.