Metal Detecting Terms

Glossary of Terms Used in Metal Detecting & Treasure Hunting: from G to M


GRIDDING - Rigid and disciplined search routes along predetermined boundaries used to thoroughly cover a metal detecting site in several directions. Markers or boundaries may be real or imaginary.

GROUND BALANCE - A condition or mode of operation in which the detector is adjusted to optimally reduce the interference that ground mineralization has on metal targets.

GROUND BALANCE (Manual) - A ground balance feature requiring manual adjustment by the operator.

GROUND BALANCE (Factory Preset) - A feature eliminating the ground control and operator manipulation. The metal detector is preset at the factory to an average range of non-conductive soils.

GROUND BALANCE (Self-adjusting) - A true automated ground balancing feature. The detector circuitry senses change in mineralization and compensates to sustain balance.

GROUND COMPENSATION - The ability of the detector to compensate for the effects of ground mineralization.

GROUND FILTER - Specialized sections of metal detector circuitry which separates the ground mineral effect from metal responses in the motion discriminate mode. Quality of design dictates the level of efficiency, sweep rate, depth penetration, and recovery time related to target separation.


HALO EFFECT - A conductive increase in target size as seen by the metal detector's electromagnetic field. The effect is caused by excessive target oxidation permeating the soil directly surrounding the target. Associated with long term burial or highly acidic soils. You can read more details on my Halo Effect page.

HAMMERED SITE - A slang term for a metal detecting site that has been searched by metaldetectorists many times. Also called SEARCHED OUT, HUNTED OUT and POUNDED SITE.

HEADPHONES (also see WIRELESS HEADPHONES) - Remote loudspeakers worn over the ears to enhance the operator's hearing ability and block ambient noise such as automobile traffic and ocean waves. A highly recommended alternative to the detector's speaker. The batteries last longer when headphones are used.

HEARING FATIGUE - A temporary condition of the detectorist's brain when its ability in processing the incoming audio signals begins to decrease. As a result, the detectorist begins to 1) hear less difference between various audio tones (when the Tone ID feature is used), and/or 2) fail discerning the solid signals from the broken ones (this happens in both Tone ID and Single Tone ID cases of usage), therefore, missing some desirable targets. Hearing Fatigue takes place when either a lot of various audio signals are incoming in a non-stop manner for a long period of time (while metal detecting at the junk littered site) or the detectorist has been metal detecting for hours without taking a break. This condition is not noticeable unless one starts feeling a headache caused by numerous cacophonous signals. That is why it is important for any detectorist to take as many breaks as possible during the search. While taking a break, one should take the headphones off and rest mentally and physically for 15 minutes. That would reset detectorist's brain to its "default condition." It is important to remember that physical fatigue dulls one's visual and hearing senses as well.

HEEL - The southern section of search coil behind the control shaft attachment point as viewed from above by the operator.

HERTZ (Hz) - Cycles per second (see FREQUENCY).

HOT ROCK - Any rock containing more non-conductive mineralization than the surrounding matrix to which the detector is ground balanced. Positive or false metallic responses can be heard from these rocks in the motion discriminate mode and a negative or null in audio threshold in the non-motion, all-metal ground balanced mode. You can read more details on my Hot Rocks page


IB - An abbreviation which stands for Induction Balance. IB is a condition of zero current flow between transmit and receive windings prior to metal detection. Basically the search coil of the induction balance detector consists of two wire loops: one is a transmitter, another one is a receiver. The most common detectors used nowadays are the detectors that utilize the inductive balance principle of metal detection.

INDUCTANCE - The electrical property of a metal target to oppose variations of the magnetic field. This characteristic is referred to as Ferrous Content.

ISOLATOR - also Lower Shaft - the lower most section of non-metallic control shaft which attaches to the search coil and separates the metallic portion of the control shaft from the electromagnetic field.


KEEPER - A slang word for a good metal detecting find.

kHZ (Kilohertz) - One thousand cycles per second, (see FREQUENCY).


LCD - Abbreviation for Liquid Crystal Display. The basis for metal detector visual graphic display technology.

LED - Abbreviation for Light Emitting Diode. A lamp-like semiconductor used for visually indicating circuit functions such as target response and battery condition.


MATRIX - The total volume of ground penetrated by the electromagnetic transmit field containing minerals, metals, salts, rocks, moisture and organic matter.

MINERALIZED GROUND - Soil containing non-conductive and/or conductive properties which directly influence metal detector tuning and depth penetration.

MINERALIZATION - An amount of non-conductive and/or conductive properties in soil or sand on seashore. Mineralization may be:

• NATURAL MAGNETIC - iron oxide, hot rocks and magnetite;
• SPORADIC (also magnetic) - at sites of former human settlement - pottery, slag, bricks, hearths and hot rocks;
• LITTORAL - at the seashore - properties of this mineralization may range from magnetic (black sand) to electrically conductive (salt water) depending on the beach or region.

MODE - A state of metal detector operation selected by the operator to accomplish a specific task.

MODULAR - A metal detector configuration in which the circuit board(s) can be easily removed and/or replaced for the purpose of repair or upgrade without replacing the entire metal detector.

MONOLOOP COIL - A search coil in which the multiple strands of wire are wound in a single loop around the circumference of the coil. Monoloop coil provides greater depth and sensitivity compared to a Double D coil of equivalent size in in soils with low-medium mineral content.

MOTION DISCRIMINATOR - A detector requiring constant search coil motion to reduce the effect ground mineral interference has on its discriminate function. In short words: search coil requires movement for discrimination to be achieved.

MOTION GROUND CONTROL - movement of a search coil is required for controlling the ground mineralization.

MULTI-FREQUENCY - Metal detector circuitry employing multiple transmit frequencies to enhance the separation of ground mineral effect from target response to increase target identification accuracy. Examples: BROAD BAND SPECTRUM (BBS) and FULL BAND SPECTRUM (FBS) technologies used by the Minelab detectors. Their circuits automatically transmit 17 or 28 frequencies simultaneously. This provides the advantage in both good depth and high sensitivity over the single- and dual-frequency metal detectors.

MULTI PERIOD SENSING (MPS) - Minelab's patented pulse induction technology. Standard pulse induction metal detectors are limited because they use a single pulse width. MPS uses varying pulse widths that extract more information from targets, achieve better ground balance and detect to greater depths.

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