15-02-2017, 03:30 PM
A metal detector is an electronic instrument that detects the presence of metal near. Metal detectors are useful for finding hidden metal inclusions inside objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe that can be swept over the floor or other objects. If the sensor approaches a metal part, this is indicated by a changing tone on the headphones or a needle moving over an indicator. Usually, the device gives some indication of the distance; The closer the metal is, the higher the pitch in the handset or the higher the needle. Another common type is stationary metal detectors "on foot" used for detecting security at access points in prisons, courts and airports to detect metal weapons hidden in a person's body.
The simplest form of a metal detector consists of an oscillator that produces an alternating current that passes through a coil that produces an alternating magnetic field. If an electrically conductive metal part is near the coil, the eddy currents will be induced in the metal, and this produces its own magnetic field. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metal object can be detected.
The earliest detectors of industrial metals were developed in the 1960s and were widely used for prospecting for minerals and other industrial applications. Uses include detection of landmines, detection of weapons such as knives and guns (especially in airport security), geophysical prospecting, archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food and in the construction industry to detect reinforcing steel bars in concrete and pipes and cables buried in walls and floors.
The simplest form of a metal detector consists of an oscillator that produces an alternating current that passes through a coil that produces an alternating magnetic field. If an electrically conductive metal part is near the coil, the eddy currents will be induced in the metal, and this produces its own magnetic field. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metal object can be detected.
The earliest detectors of industrial metals were developed in the 1960s and were widely used for prospecting for minerals and other industrial applications. Uses include detection of landmines, detection of weapons such as knives and guns (especially in airport security), geophysical prospecting, archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food and in the construction industry to detect reinforcing steel bars in concrete and pipes and cables buried in walls and floors.
