金属探测器利用电磁感应的原理，利用有交流电通过的线圈，产生迅速变化的磁场。这个磁场能在金属物体内部能感生涡电流。涡电流又会产生磁场，倒过来影响原来的磁场，引发探测器发出鸣声。
Metal detectors use the principle of electromagnetic induction, the use of alternating current through the coil, produce a rapidly changing magnetic field. This magnetic field can induce eddy currents inside metallic objects. Eddy current will produce magnetic field, which will affect the original magnetic field and trigger the sound of the detector.