Modified electric current perturbation (ECP) characterization for a circular aperture

In this paper, a modified electric current perturbation (ECP) is presented, which confines an interrogating current to its inspection region and improves inspection sensitivity by using high-frequency current distribution properties. Characterization of a circular aperture, namely, a mathematical model of the induced magnetic flux density for a radius of a circular aperture, is subsequently developed. The proposed method has the advantage that the induced magnetic flux density can be obtained only by integrating over the aperture region, due to the distribution properties. In order to confirm the validity of the mathematical model, experiments are carried out with several specimens, demonstrating close correlation with the mathematical model.