Impedance Characteristics and Analysis of Liftoff Distance Effect using Polynomial Approximation on Eddycurrent Nondestructive Testing

Development of eddy current testing makes possible for the inspection of the conductivity variations, inspection of surface and beneath the surface of conductivity materials and liftoff property to characterize nonconductive materials.This paper deals with impedance analysis and analyzes liftoff distance effect using numerical method on eddy current testing. The focus of this paper is to first characterize impedance values under measurement with ferrite pot core probe in eddy current testing. Pot coreshaping probe used in this work offers a number of advantages, including self-shielding, space efficiency, convenience, good temperature stability and low losses. In addition, utilization of pot core shaped probe makes the edge effect on test sample avoidable. Secondly, a liftoff distance effect using a polynomial model is introduced and can be mitigated on zero of liftoff distance effect for measured data. This research allows to present the possibility of pot core shaped probe utilization and analytical approach for lift off distance effect. Keyword Impedance characteristics, liftoff distance effect, multi-frequency technique, polynomial approach, eddycurrent testing.