Glossary of Terms

For more about metal detector technology and use, see our Frequently Asked Questions page.


AC (Alternating Current) – Metal detector modes that require loop motion to respond to metal.

Air Test – Testing a metal detector’s response to various metallic samples with the loop held away from the ground.

All-Metal – Describes any mode or control setting allowing total acceptance of all types of metal targets, iron and non-iron.

Audio Identification Tones – Circuitry or mode producing different audio tones (pitches) for different target types.

AutoTrac (Automatic Ground Tracking) – A feature that continually and automatically readjusts the ground balance (ground rejection) of a metal detector during searching.

Back Reading – A false target response caused by either overloading due to a very strong target near the loop, or a rejected trash target very close to the loop.

Black Sand – One of the most difficult environments for detecting because of extreme components of nonconducting negative ground mineralization. Also called (Fe304), magnetite, iron oxide, magnetic sand.

Cache – Intentionally buried or secreted hoard of valuables.

Concentric Coil – Round search loops with circular coils that are the most common design.

Conductive Salts – One of the major mineral types which makes up the positive ground matrix. Wet ocean salt and/or sand will produce a positive indication much like a metal target.

Conductivity – The measure of eddy currents of electricity that generate on a metal’s surface.

Custom Program – Feature choices on a computerized metal detector that are then saved or stored for future use.

DC (Direct Current) – Used to refer to metal detector modes that do not require loop motion to respond to metal targets.

DD Coil – A search head with coils arranged like a mirrored capital “D” that has a detection field shaped like a rectangular band instead of a cone.

De-tuning – A method of narrowing a target signal’s width and length for precise pinpointing.

Depth – How deep in the ground a detector range extends to find and react to metal targets.

Depth Reading – Feature that indicates how deep a target is in the ground before digging.

Detection Pattern – The shape of the electromagnetic detection field generated by a metal detector’s loop.

Digging – The recovery of a detected target through excavation, whether with simple or advanced methods.

Discrimination – Adjustable feature that can ignore or respond to different metal types based on their amplitude and phase. Used to cancel responses of unwanted trash metals.

Drift – A loss or increase in threshold caused by the passage of time or variations in temperature.

Eddy Currents – Small circulating currents of electricity on the surface of metals produced by external electromagnetic fields.

Electromagnetic Field – An invisible force extending from the detector’s loop created by the flow of alternating oscillator frequency current around the transmit winding.

Elliptical Coil – A detector loop with an ellipse (oval) shape that increases ground coverage per sweep for a given weight. Pinpointing with this style of loop may take more practice for operators used to a concentric coil.

False Signal – Erroneous signal caused by non-metal items.

Faraday Shield – Conductive coating inside loops, loop cables, and control housings to eliminate electrostatic interference.

Ferrous Oxide – Ferrous oxide is decomposed particles of iron, also known as mineralization.

Frequency – The number of complete alternating current cycles produced by the transmit oscillator per second. Measured in Hertz (Hz) or cycles per second.

Frequency Shift – Changes the operating frequency, suppressing the interference (cross talk) between detectors.

Fringe Target – A target so deep or so small as to be barely detectable with a metal detector.

Ground Balance – A feature that can be adjusted to ignore the masking effect ground minerals have over metal targets.

Ground Matrix – Total volume of undisturbed ground, usually contains varying amounts and combinations of minerals, moisture, and salt. In an undisturbed condition the ground matrix can exhibit numerous effects on metal detector performance.

Hipmount – A configuration where the control box of a metal detector is mounted on the operator’s hip, limiting the weight one has to sweep to that of the loop and rod assembly.

Hot Rock – A rock that contains a higher concentration of metallic minerals than the surrounding ground.

Interference – Hindrance of performance due to sources outside a metal detector causing static and unwanted or false signals.

LCD (Liquid Crystal Display) – A digital display used for graphic visual indications as an alternative to the use of analog meters.

Loop (Search Coil) – The end of the metal detector that is swept over the ground. It contains two coils of wire that work together to generate an electromagnetic field and measure the effect on it by metal targets that come within range.

Memory – A computerized metal detector’s ability to retain operator selected settings for future use.

Menu – A display screen that allows the operator to choose among different features.

Metal – Metallic substances: iron, foil, nickel, aluminum, gold, brass, lead, copper, silver, etc.

Meter – An analog component which provides visual indications regarding a metal target as an alternative to LCD displays.

Microprocessor – An electronic component (chip) that can be programmed to perform a variety of functions and control a variety of features.

Mineralized Ground – Any soil or sand that contains conductive and/or magnetic components (minerals).

Mixed Mode – A special metal detector mode that combines all-metal and discrimination features into one operating mode.

Mode – A condition of operation selected by the operator for specific functions or ideal operation in special environmental conditions.

Motion Instrument – A detector type that requires search loop movement to activate the signal from a metal target.

Negative Ground – Soil containing mostly magnetic minerals.

Neutral Ground – Soil that contains no significant minerals.

NiCad (Nickel Cadmium) – A battery type that can be recharged.

NiMH (Nickel–Metal Hydride) – A battery type that can be recharged.

Non-Ferrous – Metals that are not-of-iron and are in the precious and semi-precious class: aluminum, brass, lead, gold, silver, copper.

Non-Motion – Operation mode that will respond to metals with or without movement of the loop.

Notch Discrimination – Discrimination circuitry that allows an area of the discrimination range to be accepted or rejected independently of the remaining discrimination range. A window of acceptance or rejection within the discriminate range, or a discrimination-within-discrimination.

Notch Width – Finite range of a notch discrimination setting determining how wide of a window is accepted or rejected.

Null – A decrease in sound caused by rejection of targets or ground mineralization.

Oscillator – An electronic component or circuitry designed to generate a specific rate of current frequency to power the loop’s transmit winding.

Overlap – Advancing each sweep of the loop in small increments to insure good area coverage. Each sweep should overlap the last by at least 50%.

Overload – Occurs when the receiver of a metal detector becomes overwhelmed because of too much signal from ground and/or target.

Overshoot – A false signal heard as the loop passes over a rejected target when using a non-motion discriminate mode in combination with automatic tuning. Excessive tuning restoration pushes the audio above the threshold level creating a positive response at the edges of target detection.

Phase – The length of time between eddy current generation sustained on a metal’s surface and the resultant secondary electromagnetic field effect on the loop’s receive winding. Phase relates to target conductivity.

PI (Pulse Induction) – A type of metal detector circuitry that operates differently than the standard Transmit Receive or Very Low Frequency instruments. These specialized detectors cannot identify or reject iron, and they are primarily recommended for better results in salt water and other highly mineralized ground.

Pinpointing – Finding the exact target location with respect to the loops physical center.

Positive Ground – Soils that contain conductive components such as salt.

Preset – A control setting or marking determined to work well for average conditions.

Preset Program – An operational mode of a computerized metal detector that automatically selects all the features suited to a particular type of searching condition.

Prospecting – Searching for gold in its natural state (nuggets).

Rejection – Non-acceptance or cancellation of response to a target by discrimination circuitry.

Relic – An artifact of the past.

S.A.T. (Self Adjusting Threshold) – Automatically resets the threshold to correct for any minor ground, temperature, or electrical changes that typically cause threshold variations.

Scrubbing – Sweeping the loop with contact to the ground.

Search Coil – See “Loop” definition.

Sensitivity – Measure of a detector’s ability to respond to targets within the detection pattern. Usually indicates the capability to respond to small targets rather than maximum detection depth.

Signagraph – A graphic display of a pattern characterizing a target’s electrical and/or magnetic properties.

Signal – An audio response or visual indication alerting the operator that a metal target has been detected.

Silent Search – Capability of a metal detector to respond to metals without a threshold or background sound being heard continually during searching.

Spider Coil – A search head with concentric coils in a circular loop pattern and extra bracing for stability.

Stability – The ability of a metal detector to maintain smooth operation despite interference or unstable environment.

Target – Any object that causes a metal detector to respond.

Target Masking – When extreme ground mineralization or the large size or high concentration of trash metals drive the threshold into the null zone, suppressing weaker positive responses.

Ten-Turn Control – A control knob which can be rotated ten times to cover the full electrical range of the feature.

Test Garden – A mapped plot of buried targets at various depths to aid in learning the characteristics of a metal detector.

TH’er, TH’ing – Universal word contractions for treasure hunter and treasure hunting

Threshold – The background hum heard continually during the use of a metal detector indicating the most sensitive audio.

Tone Control – An adjustment for audio frequency or pitch.

Touch-Pad – Switches encapsulated in plastic that allow the operator to select different functions or features.

TR (Transmit Receive) – Term used to describe early metal detector technology. Usually describes non-ground rejecting detectors or modes.

Transmit Coil – A coil of wire inside the loop that creates the primary electromagnetic field.

Trash Metal – A type of metal that is undesirable and thus removed from a metal detector’s response indicators using discrimination settings. Lead and aluminum are the most difficult common trash metals to eliminate.

Two Box – A metal detector that has the transmit and receive coils mounted in separate housings. By enlarging and separating the transmit and receive coils, great depths regarding large metal items can be achieved. Also called cache detectors.

Viewing Angle – A liquid crystals display adjustment for contrast allowing optimum visibility for various light conditions.

Visual Discrimination – The ability of a metal detector to communicate trash or non-trash by means of visual indications.

Visual Discrimination Indication (VDI) – A visual indication as to the type of target a metal detector is detecting.

VLF (Very Low Frequency) – Generally used to refer to metal detectors that can cancel the effects of ground mineralization, typically with operating frequencies in the 3-30 kHz range. This is the most developed technology used in modern metal detectors, capable of discrimination, ground balance, and pinpointing modes, and microprocessor control.

VLF/DISC – A detector that can cancel ground mineralization while at the same time discriminate against trash.

Voltage Regulator – Circuitry that controls the amount of electricity supplied to operate a metal detector with no loss in performance over a specific voltage/current range.

Winding – Coiled wiring in the search loop that creates electromagnetic fields or receives metal target’s effects on the field.

Zero Discrimination – Used to describe detectors whose discrimination control allows the acceptance of all types of metals when set to the zero position.

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