Back كاشف المعادن Arabic Metoidedektor BAR Detector de metalls Catalan Detektor kovů Czech Metaldetektor Danish Metalldetektor German Metaldetektilo Esperanto Detector de metales Spanish Metallidetektor Estonian Metal detektagailu Basque
A metal detector is an instrument that detects the nearby presence of metal. Metal detectors are useful for finding metal objects on the surface, underground, and under water. A metal detector consists of a control box, an adjustable shaft, and a variable-shaped pickup coil. When the coil nears metal, the control box signals its presence with a tone, light, or needle movement. Signal intensity typically increases with proximity. A common type are stationary "walk through" metal detectors used at access points in prisons, courthouses, airports and psychiatric hospitals to detect concealed metal weapons on a person's body.
The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced (inductive sensor) in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected.
The first industrial metal detectors came out in the 1960s. They were used for finding minerals among other things. Metal detectors help find land mines. They also detect weapons like knives and guns, which is important for airport security. People even use them to search for buried objects, like in archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel reinforcing bars in concrete and pipes and wires buried in walls and floors.