Model of a Novel PCB Coil for High-Sensitivity Metal Detector

Metal detectors detect hidden metal objects through electromagnetic induction. Significant research has focused on improving the detector sensitivity by redesigning the structure of differential receiving coils. Higher sensitivity allows the detector to identify smaller metal objects or detect objects at greater depths. This is significant in applications such as security screening and industrial quality control, where precision is essential. This paper introduces a novel receiving PCB coil prototype for a high-sensitivity metal detector and presents a numerical modeling method to optimize the coil size. The strip coils distributed around the emitting coil are employed in the differential receiving coils, thereby strengthening the induced voltages caused by the electromagnetic field excited from the detected metal objects. The balance state of the differential receiving coils is analyzed using a numerical model based on the Biot-Savart law, solving the total magnetic flux from the emitting windings. An optimization problem is constructed from the numerical model, and the optimal design parameters of the receiving coil are determined via a heuristic algorithm. Experimental results indicate that the newly designed prototype exhibits superior sensitivity compared to commercial differential detectors of comparable size. Specifically, the sensitivity of the novel detector is twice that of the advanced commercial counterpart.