A simplified model for non-destructive thickness measurement immune to the lift-off effect

A simplified model for thickness measurement was introduced in this paper by using an electromagnetic sensor. It uses the phase signature of inductance change to reduce the lift-off effect when air-core coil is placed next to a thin nonmagnetic metallic plate. The phase signature can be extracted through the data at several frequencies. The thickness of the plate can be evaluated non-intrusively and directly. Numerical simulations were carried out for different plate thickness. The results validated the effectiveness of the proposed model when used in eddy-current testing.