A hand held metal detector is an musical instrument that detects the presence of metal nearby. Metal detectors are useful for locating metal inclusions hidden within objects, or metal objects buried underground. They often contains a handheld unit with a sensor probe which may be swept over the bottom or other objects. If the sensor comes near a bit of metal this is often indicated by a changing tone in earphones, or a needle moving on an indicator. Usually the device gives some indication of distance; the closer the metal is, the upper the tone within the earphone or the upper the needle goes
The usage of handheld detector is various and enormous . In some public occasions the hand-held detector are often used for peace check like airports, jails, courts, testing centers, banks, hotels, bull sessions, athletic contests, vocal concerts then on. In some factories handheld metal detectors are wont to prevent the thievery who stole some products which contain metals. because the technology develops some student use tiny wireless headsets to cheat while testing, so as to against this behavior the education system requires the guards held a handheld detector outside of the examination room.