Eddy current testing method and eddy current testing apparatus

摘要: The present invention provides an eddy current testing method and apparatus that can reduce detection noise to increase the SN ratio thus improving defect accuracy. An sensor includes a pair of excitation coils coil disposed therebetween. For example, voltage regulator applies voltages having different amplitudes so as caused by deformed portion heat exchanger tube plate in signal coil. Alternatively, for detector first frequency f 1 , at which material is reduced negligible amplitude, second 2 higher than sensor. phase gain measurement waveform with are adjusted then differential frequencies obtained based on induction detected cancel out expansion noise.