金属探测器是如何工作的？

How does a metal detector work?

工业金属探测器可有两种方式安装。可以在传送带上输送的产品上面或下面安装板式线圈。但更灵敏的探测器则应该让产品穿过线圈并将线圈安装于金属壳内。这种更灵敏的线圈型，其中通常装有3个线圈——1个中心发射线圈和2个绕向相反的接收线圈装在一个探头内。与中心线圈相连的振荡器产生一个高频磁场。而两个绕向相反接收线圈相互连接，以便在磁场未受干扰时可将它们所产生的感应电压自相抵消。

Industrial metal detectors can be installed in two ways. Plate coils can be mounted on or below the products that can be conveyed on the conveyor belt. But the more sensitive detector should let the product pass through the coil and install the coil inside the metal shell. This is a more sensitive coil, usually equipped with 3 coils - 1 central emission coils and 2 opposite receiving coils in a probe. The oscillator connected to the central coil produces a high frequency magnetic field. The two winding coils are connected to each other so that the induced voltage produced by the magnetic field can be counteracted in phase when the magnetic field is undisturbed.

为了获得最佳灵敏度，金属探测器的孔径尺寸应该与特定的产品大小相匹配。孔径太大，会有„削弱‟信号的危险；而孔径太小会不便于产品在传送带上通行。探测器的灵敏度通常是从由孔径的几何中心测量得来的 —— 最不敏感的几何点。当被金属污染的产品通过时，隐含的金属物对探测器的磁场产生干扰现象，两个接收线圈的输出信号不能相互抵消，从而探测出金属杂质的存在。

To obtain the best sensitivity, the size of the metal detector should match the size of a specific product. The aperture is too large, there will be a "dangerous" weakened signal; and the aperture is too small will not easily pass products on the conveyor belt. The sensitivity of a detector is usually measured from the geometric center of the aperture - the most insensitive geometry. When a metal contaminated product passes, the hidden metal interferes with the magnetic field of the detector. The output signals of the two receiving coils can not cancel each other, so as to detect the existence of metal impurities.