The flow of eddy currents is affected by fissures, constrictions or other discontinuities that cause distortions in the cross section through which the current is made to flow. Thus, the eddy current technique is useful for detecting the wall thickness of thin materials as well as measuring localized discontinuities
The thickness of the part must be within the depth of penetration (skin depth), eddy currents is dependent upon material properties and operating frequency.
This method can detect very small flaws in or near the surface of the material. Changes in material thickness, and changes in material properties can also be measured