Eddy current sensors, based on the eddy current mutual inductance effect, are sensing devices capable of high-precision detection of internal defects and minute displacements in measured objects. Due to their significant advantages such as non-contact measurement, wide frequency response, and strong resistance, they are widely used in important fields such as non-destructive testing of equipment and online condition monitoring. However, with the continuous expansion of the testing field and the rapid increase in testing requirements, conventional eddy current testing technology is not suitable for detecting minute defects. In recent years, relying on microelectromechanical systems (MEMS) and flexible manufacturing processes, it is possible to manufacture eddy current sensor probes with flexible and diverse structures, enabling miniaturization, arraying, and flexibility of eddy current sensor probes, featuring high sensitivity, high signal-to-noise ratio, and fast response. Array probes have become a current research challenge and hot topic in eddy current testing technology.
In eddy current testing, the performance of the array probe determines the eddy current detection results, and the electrical parameters of the array probe directly affect parameters such as linearity and sensitivity. Traditional eddy current sensor probes are mostly fabricated using the wire-wound method, with abundant empirical formulas. To achieve higher detection accuracy and reduce the size of the array probe coil unit, planar helical coils are often used. However, planar coils have low inductance, and only at higher operating frequencies can the ideal quality factor Q be achieved. To obtain better performance, a double-layer planar helical coil interconnection structure is adopted, but this structure lacks empirical formulas for calculating electrical parameters. This paper uses an analytical method to calculate the inductance, resistance, quality factor, and other electrical parameters of the double-layer planar helical coil, effectively shortening the numerical calculation time and improving the efficiency of eddy current sensor probe design. This has important guiding significance for the design of eddy current sensor probe coil structures.
