What Can Metal Detectors Detect?by Kathryn Hatashita-Lee
Metal detectors are electronic devices that feature a large coil of wire, or transmit coil, and a second coil of wire, the receive coil, that indicate buried metal via a speaker. Basic types include industrial and security, general prospecting, gold prospecting, underwater and salt beach, cache hunting and deep searching.
Metal detectors detect iron, nickel, copper, brass, aluminum, tin, lead, gold, silver and bronze. General-purpose metal detectors can find buried metal objects such as jewelry, coins and other metal objects. "Discrimination" is a process that distinguishes between different metal targets or alloys. For example, an audio type of discriminator can be set to send sound signals that indicate metals of interest such as nickel and reject pull-tabs.
The very-low-frequency metal detector (VLF) can pick up strong signals from ferromagnetic substances such as grains of iron-bearing minerals in the sand or soil. According to the University of Alaska, a metal detector receives a signal from these particles and their conductive properties in the ground thousands of times stronger than a signal from a small metal object. However, a metal detector adjusted as "ground balanced" will more accurately target metal objects such as coins or jewelry. High-frequency detectors can target natural gold.
The electronic devices have many industrial applications such as in the military, airports, food processing plants, construction and the garment industry.