METHOD FOR MEASURING S/N RATIO IN EDDY CURRENT TESTING ON INTERNAL SURFACE OF PIPE OR TUBE

摘要

A method in accordance with the present invention includes the steps of: separating an eddy current signal into an X-axis component and a Y-axis component to obtain signal waveform data of the respective components; excluding predetermined low-frequency components respectively from the respective signal waveform data thus obtained; calculating a noise voltage value V1 defined by the following Equation (1) based upon voltage values X(i) and Y(i) of the signal waveform data of the X-axis component and the Y-axis component from which the low-frequency components have been excluded; and calculating an S/N ratio by dividing a voltage value D of an eddy current signal corresponding to a predetermined artificial flaw by the noise voltage value V1: V �¢ 1 j = À / n ‹ ˆ‘ i = 1 n X �¢ i 2 + Y �¢ i 2 1 / 2 where n represents the number of samplings of the signal waveform data.