ABSTRACT
In eddy current (EC) testing, a fundamental requirement is that the examined material has induced in it a distribution of currents. This restricts the technique to those materials that are electrically conductive. The currents within the inspected materials are formed in response to a changing electromagnetic field that is generated by a changing current in a conductor that is placed in close proximity to the material. They are constrained to the flow in closed loops within the inspected material, and themselves generate magnetic fields. These fields, in combination with the fields that excite the currents, must be detected either by electromagnetic induction in a coil, or a system of coils, or by sensors such as the halt element. In many cases the same coil is used both to excite the circulatory (eddy) currents, and also to detect their fields.
