Performance Investigation of Multi-Turn Pickup for Circular Fractal Flexible Planar Eddy Current Probe

This paper aims to compare and analyze the performance differences between a single-coil and multi-coil pickup coil layout in a flexible circular fractal planar eddy current probe. Flexible planar eddy current probes offer flexibility and adaptability, making them widely used in the detection of complex structures. The circular fractal flexible planar eddy current probe is a new type of probe that has a lower miss rate in detecting cracks at specific angles compared to traditional circular and rectangular coil eddy current probes. However, the single-coil structure of the probe's pickup coil has the drawback of being less sensitive to weak signals. This paper investigates the detection performance of the flexible circular fractal probe by varying the number of turns in the original pickup coil. Experimental comparisons were conducted by preparing and installing single-coil and multi-coil circular fractal planar eddy current probes. The performance differences between single-coil and multi-coil configurations were compared and analyzed under various excitation frequencies, liftoff distances, and internal crack depths. The results showed that, compared to the single-coil probe, the multi-coil probe exhibited significantly improved detection signal values and sensitivity.