S/N Ratio Measuring Method 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: $\begin{array}{cc}V1=\mathrm{pi}/n.\sum _{i=1}^n{\left({X\left(i\right)}^2+{Y\left(i\right)}^2\right)}^{1/2}& \left(1\right)\end{array}$ where n represents the number of samplings of the signal waveform data.