Design and Characterization of PCB based Planar Coil Eddy Current Probes

Eddy current based NDT is typically adopted to detect surface defects in rails caused by wheel-rail contact. Printed coil planar eddy current probes have advantages of ease in manufacturing using conventional PCB fabrication techniques. In this work, we present the design and characterization of two kinds of such PCB based planar eddy current probes. While the first design is a differential T/R coil, the second design is a differential T/R coil. Such printed coil eddy current probes, not only provide enhanced sensitivity, but improved lift-off immunity useful in detection of sub-surface cracks. The design has been carried out using efficient FEM based full-wave electromagnetic simulation technique. Analysis and design optimizations have been performed for enhanced sensitivity. Both the designs are compared in terms of sensitivity and in general, the results obtained from both simulations and experimental testing confirm the effectiveness of such PCB based planar coil EC probes in detecting surface cracks.