Metal detectors are electronic instruments that are used to detect the presence of metal if it is in close proximity. They can be particularly useful for finding metal that may be underground or hidden and are often used for archaeological purposes.
Different metal detectors can work in different ways, depending on their uses, but in a simple form they usually consist of a transmitter coil, through which electricity flows to create a magnetic field. This turns the metal detector into an electromagnet. By moving the detector, the magnetic field that has been created is moved too and when it comes close to another metal a second magnetic field is created which is what the detector is looking for. There is another coil, called a receiver coil, on the detector that will usually emit a noise when it comes into contact with the magnetic field. Generally, the stronger the magnetic field is the louder the noise will be to indicate how close you are to the metal object.
Metal detectors are also used for security purposes in places such as government buildings and airports. Since the 1970s, metal detectors have been largely used across the world in airports to screen passengers before they board a flight. In addition to this, security officials are often in possession of smaller hand-held devices that can be swept over the body to detect metal.
Anyone can own a metal detector and in England and Wales their use is not prohibited, providing that permission has been granted by the landowner of the area they are to be used on. The only exclusions are if the area in question is a Scheduled Ancient Monument, an SSSI (site of special scientific interest) or falls under the Countryside Stewardship Scheme.