Metal detector is an electronic instrument used to locate lost or concealed metal. In the presence of metal, a metal detector gives off a sound, a visual signal, or a vibration. Prospectors, coin and relic hunters, and archaeologists use metal detectors to search for lost or hidden metals or metal objects. Police officers and security personnel use metal detectors to check people for concealed weapons. Manufacturers use detectors to screen packaged goods to ensure that metal objects have not accidentally entered products, especially food products.
Metal detectors vary in design, size, and shape. They may be small enough to hold in the hand or large enough to walk through or to pass a large object through. Many metal detectors indicate whether a detected metal is precious or non-precious. Some can estimate a metal’s distance from the detector.
All metal detectors operate using one of two basic electronic principles: inductive balance or pulse induction. A metal detector with inductive balance generates a continuous electromagnetic field, a region around the device where electric and magnetic force can be felt. A metal object absorbs, distorts, and reflects portions of this field, and the detector signals when variations occur. In a detector with pulse induction, the electromagnetic field pulses on and off. A metal object absorbs a portion of this field, and receiver circuits detect this effect when the detector is pulsed off.
