Pulse eddy current (PEC) testing is broadly used as an effective nondestructive testing technique especially for the defect detection of multiple layer and irregular surface objects. PEC testing's adoption of repeated pulses as excitation provides for the penetration of many frequency components into the piece being tested and returns more information from various depths. As the lift-off height will inevitably change during detection, the lift-off effect serves as a significant obstacle to implement effective nondestructive testing and further evaluations. This paper concentrates on improving the probe's immunity to the lift-off effect and proposes two-stage PEC differential probes. Physical experiments are addressed in this paper. Experimental results demonstrate that two-stage differential PEC probes are able to suppress lift-off effects.
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