Research On The Metal Thickness Measurement Of Pulsed Eddy Current

Now, in the industry manufacture and equipment testing, there are several methods for the metal thickness measurement, as ultrasonic,X-ray, eddy current and so on. One of these testing methods, eddy current, has been widely used for metal thickness measuring because of its good sensitivity, high test speed , non-contact and other advantage. The principle of eddy current testing is that, when the test coil is close to the metal conductor with alternating current, the eddy current would be inducing in the conductor, and correspongdingly, the eddy current would affect the original magnetic field, the result is the coil's impedance and inducing voltage changed. So we can get the information of metal from analyze the change.Pulsed eddy current techniques is a new nondestructive testing technology developed in recent years, which contains a string of frenquencies and more information than conventianl eddy current techniques, but lift-off effects is still a main obstacle for this new technology.This study mainly shows how to alleviate lift-off effects for measurement of non-ferrous metal thickness via introducing lift-off intersection point(LOI) to analyze pulsed eddy current signals. The results from simulation and experiment show that applying LOI information to metal thickness measurement can get well effect and achieve accurate measurement. At last, on the base of experiment, a equipment of PEC thickness measurement is built up.Finally, the conclusion of this paper is given and the suggestion for further research is provided.