Study of a new surface eddy current probe without lift-off noise

摘要

The authors propose a new surface eddy current probe without lift-off noise. The basic concept of the probe is that it does not detect the eddy current induced by the exciting coil when the test material has no flaw and detects only that eddy current which is generated by a flaw in the test material. The new eddy current probe, called Θ probe, consists of a pancake exciting coil and a tangential detecting coil. Experimental results with the new probe have indicated that it generates far less lift-off noise than the conventional surface probe. The flaw signal phase changes according to flaw depth but is changed little by the length, width, and direction of the flaw. The new probe makes it possible to estimate flaw depth based on the flaw signal phase and greatly improves the depth evaluation accuracy of slit flaws in eddy current testing.