pagesHow Do Metal Detectors Work?
Metal detectors are devices that are used to detect metal objects in the soil, on people or in cargo. These metal objects can be discarded pieces of aluminum, jewelry, coins, and tools and can be buried underground. Metal detectors are also used in humanitarian, industrial and security fields. Knowing how a metal detector works helps people to use them more effectively.
A metal detector is made up of 4 main parts. The stabilizer, control box, shaft and search coil. The search coil can also be called a search head, search loop or antenna. The stabilizer is mainly used in handheld detectors near the handgrip area. The control box or brain of the detector consists of a microprocessor, circuitry, speaker, controls and in the handheld, batteries. A shaft of the handheld detector connects the control box and search coil and is adjustable to accommodate the height of its user. The search coil, the most important part, is the part that senses metal objects.
The principle behind all detectors is the principle of electromagnetism and its effect on conductive metals. The transmitter in the search coil generates a penetrating electromagnetic field. This field can detect objects below ground level because it has caused the item to become charged with magnetism. A signal is sent back through the control box and into the speaker system, signaling the user that something has been found. Newer metal detectors can actually display the type of metal that is found as well as how deep the objects are.
Of course, the same basic technology is used for a walk through metal detector that you see in most airports and courthouses. The various technologies are very low frequency or VLF, pulse induction or PI and beat frequency oscillation for BFO. The most popular technology today is VLF technology.
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