Hunting for treasure has always been an activity that has fascinated both the young and the old. While earlier attempts at discovering treasure were concentrated around the correct interpretation of maps left behind by people who had supposedly buried the treasure, modern-day treasure hunters are further assisted by devices that can locate underground metal with ease, without any need to dig for it.
Devices that work as metal detectors work in many different ways, but the science behind all of them is more or less the same. These metal detectors have a coil of wire wrapped around the head of the detector which is often circular. When this transmitter coil, as it is called is energized with electricity, it creates a magnetic field all around it. As the metal detector is moved around the area being scanned for metal, the magnetic field also moves with it. When it encounters any metal, this magnetic field creates an electrical activity and magnetism in the metal so detected. Metal detectors have a second coil of wire, the receiver coil, which is connected to a loudspeaker. When this receiver coil detects electricity, the loudspeaker clicks or beeps, thus indicating the presence of metal. The closer you are to the metal, the louder will be the sound you hear from the loudspeaker.
Most devices used to locate underground metal, work to depths of about 2 feet or less, though there are larger more sophisticated devices that can find metal at even greater depths. This depth of detection can also be dependent on the type of metal, and its shape and size. Their orientation can also matter, as a metal piece that is buried flat will present a larger target area for the magnetic field to affect. Metal also corrodes, and if it has corroded or got oxidized, it can hamper its ability to get magnetized to create the electrical field needed for its detection. The nature of the soil in which the metal objects are buried can also affect their detection.
A basic metal detector will have a search coil, a shaft that connects the coil to the control box, and the control box which has controls, circuitry, speakers, batteries and a microprocessor. You can also have a jack that allows the user to use headphones instead of the speakers. The polarity of the magnetic field is always perpendicular to the search coil, and this allows the magnetic field it creates to be pushed deeper into the ground.
Metal detectors can determine the depth of the buried metal object based on the magnetic field strength that it generates. Metal detectors have also been found useful to detect guns and other lethal metal objects, and hand-held models are commonly used by security agencies. You must be familiar with metal detector frames that you have to pass through before you are allowed to board an aircraft, or are allowed entry into events, where there are high concerns for security. Detectors can also be used for the location of utilities buried in the ground.