Maryland Free-State Treasure Club

How Metal Detectors Work

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For an excellent explanation about how metal detectors work including metals, alloys, ghost signals, the electronics and much more, Click here
(written and compiled by Vanessa Lebeau)

     Metal detectors run from the $200 basic models to the very sophisticated $7000 and up. Cheaper models, under $100, work well for surface objects but are not recommended for targets deeper than 3-4 inches.

     No matter the price, all metal detectors work on the same principle: they transmit an electromagnetic signal into the ground via the transmit coil and receive information about the conductivity of objects buried via the receive coil. A circuit board analyzes the signal and relays information about the target to the user through headphones and/or visual readout.Search Coil

     The coil, or loop, is swept from side to side close to the ground as the user advances. When a signal is heard the headphones and/or visual readout can indicate a "good" or a "junk" target.

     Once a good target is located, the coil is also used to pinpoint the exact center of the target and its depth.

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     The target is dug by use of a digging tool or trowel in a manner that does not leave any visual evidence or damage to the soil. A cloth is used for excavated soil and an optional manual pinpointer finds the target in the matrix. Once the target is recovered, the cloth is used to dump the excavated dirt back into the hole, and the original "plug" is replaced and packed down with the foot until even with the surrounding turf in a manner that leaves no visible trace of digging.

     Some junk targets can sound like good targets and if recovered must be carried out and disposed of properly. Along with plenty of treasures, an aggressive detectorist will also recover a bag full of rusty nails and bolts, pieces of iron, pull tabs, bottle tops, aluminum foil and crushed cans. With plenty of practice and some advice from the pros, a novice can learn how to avoid much of the trash.

     Once you learn your detector's "personality" you will find less junk and more good targets such as old coins, recent coins, Civil War relics, valuable artifacts, gold and silver rings and jewelry.

     Equipment often used by detectorists include the detector, knee pads, gloves, digging tool, collection bag, manual pinpointer, a piece of cloth, snacks and water.

Happy Hunting!