Metal detectors are used to detect hidden metallic items such as firearms, treasure and minerals, etc. There are various types of metal detectors available. Security metal detectors and walk through metal detectors are devices that are used by security personnel to detect if a person is carrying firearms or if a piece of baggage contains hidden munitions. These detectors are used at airports, court houses, prisons, schools, government agencies, and many types of public gatherings such as concerts and sporting events, etc.
Metal detectors are also used by surveyors to detect subsurface metal ores and by archeologists to scan archaeological sites or soil heaps for ancient metallic items. You may even see metal detectors at the beach, where treasure hunters are sure to find all types of metal bounty.
Metal detectors are built on the principle of electromagnetic induction and there are various models such as frequency oscillator detector, induction balance detector and a pulse induction detector. A typical hand held metal detector is made up of just a few parts. An optional stabilizer keeps the detector steady as you sweep it from side to side. A control box houses the electrical components such as circuitry, controls, speaker, batteries and the microprocessor and a search coil senses if there is any metal present.
While metal detectors were commonly used in the past as a form of hobby to find hidden coins and jewelry, etc. in the sand and dirt, they are predominantly used as a form of security measure and these days. You will find that metal detectors are used all over the world for this reason.
Metal detectors are available as upright models such as in walk through metal detectors that are placed at entry points of buildings. Visitors pass through the detectors and if any hidden firearms, knives or other types of metal are present, the metal detector gives a warning to its operator. Also available are portable metal detectors, which may be carried around by security personnel who scan the ground or baggage for hidden metals.
Metal detecting wands are also used and these are generally used to frisk a person and find any hidden metal items they are carrying or wearing. Some countries forbid the use of metal detectors unless they are approved by law enforcement agencies. Alexander Graham Bell, the man who invented the telephone, also invented the first metal detector.