Study on metal tag identification impedance characteristics based on eddy testing

A crack is definitely harmful in metallic components, yet it is maybe useful in a metal barcode label (MBL) application which is a special barcode made up of tiny notches and spaces sculptured in the surface of the un-supporting parts of a metallic component. The obvious different requirement from the eddy current testing (ECT) applied in a non-destructive evaluating (NDE) is that an ECT must distinguish elements (notches and spaces) with high resolution for the high barcode density in a MBL. To achieve the optimal detection performance, the electromagnetic signals induced by MBLs must be studied under various conditions. In this paper, the impedance change of coils with various geometries and electromagnetic (EM) parameters has been given caused by the elements with various geometries and EM parameters, based on the ECT technique. Also the coverage is investigated, in which an element can effect on the coil impedance. The resolution of the MBL is defined and the characteristics of the coil impedance change caused by a MBL containing multiple elements have been analyzed.