Probe lift-off compensation method for pulsed eddy current thickness measurement

Abstract

The pulsed eddy current nondestructive testing signal for ferromagnetic plate thickness testing is sensitive to the plate's thickness and probe lift-off effect simultaneously. This feature leads to the difficulty of eigen-value extraction in thickness quantification. To remove the probe lift-off effect, a method based on calculating the time-varied relative magnetic flux changing rate is presented. Experiment result shows the relative magnetic flux changing rate is approximately lift-off independent and only determined by the plate thickness.