Multi-Layer Magnetic Focusing Sensor Structure for Pulsed Remote Field Eddy Current

Pulsed remote field eddy current (PRFEC) technique has been utilized broadly in the detection of tubular material because of its abundant frequency spectrums with lower power consumption. A novel multi-layer magnetic focusing sensor structure is proposed for PRFEC. The new sensing structure consists of several promising characteristics. It significantly enhances the detectability of the deeper depth of ferromagnetic material, and provides detection capability without covering U-type component. Both driver and receiver coils are integrated in the same sensing structure while the traditional methods are put them separated. The theoretical derivation based on electromagnetic principles has been developed for analyzing and interpreting the results. In addition, number of experiments and simulations on different defects have been studied. In experiments, both surface and subsurface defects with different width, depth, inclined angle, and circular type have been carried out. The results have confirmed that all types of defects can be detected and it has shown the relatively preferable linear relationships and reliabilities.