Glossary of Metal Detecting 

Here is our glossary of Metal Detecting terms.

Select a letter to jump to that particular section.



  • Air Test : A test to determine at what approximate settings various metal samples are rejected or accepted. Various metal samples are moved over the coil at varying distances to determine audio or visual responses from the metal detector. Air tests are not accurate and are a rough guide only.
  • Alkaline : A non-rechargeable battery that can sustain longer periods of current drain with greater storage life, compared to basic carbon-zinc type batteries.
  • All Metal : Any operating mode (or control setting) which allows total acceptance of any type of metal targets regardless of their conductive or ferrous properties.
  • Audio ID : Circuitry informing the operator of target conductivity levels by means of sound.
  • Auto Tune : Circuitry which continuously restores the detector's initial threshold audio level. The retuning rate following target rejection or drift can be preset or variable.
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  • B

  • Back-Reading : A false signal caused by a rejected target coming within one inch of, or contacting the search coil bottom, when operating in the discriminate mode.
  • Black Sand : One of the most extreme components of non-conductive, negative ground minerals. Found on beaches and in gold bearing regions. Also called magnetite or magnetic iron oxide.
  • Body Mount : A configuration whereby the control housing is separated from the control shaft and attached to the operator's body by straps or fixed to a belt. This lessens arm fatigue, aids manoeuvrability and expands usability when searching in shallow water. Also known as hip mount.
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  • C

  • Cache : A collection of coins and/or valuables that have been intentionally buried or secretly hidden. Also known as Hoard.
  • Camlock : A lever that quickly locks or releases some of the detectors components for removal or adjustment - usually the stem or shaft.
  • Coil : A plastic housing (usually circular) containing single or multiple Transmit and Receive windings (wire coils) in a specific configuration. The coil Transmits and Receives signals to, and from, the ground and metal targets. Also called loop, search coil or head.
  • Coin Depth Indicator: A visual indicator used in conjunction with calibrated circuitry to indicate the depth of buried coins or coin sized objects. Uncalibrated (smaller or lager) targets will not be measured accurately.
  • Concentric Coil : A type of Coil that has an outer ring shaped wire winding (Transmit), and a smaller inner ring shaped wire winding (Receive). Both windings are on the same plane horizontally.
  • Conductive Salts : One of the major mineral types of the positive ground matrix. Wet, ocean-salt sand produces a positive rise in threshold audio in an unbalanced, non motion, all metal mode and false signals in motion discrimination mode.
  • Conductivity : The measure of a metal target's ability to allow eddy current generation on its surface.
  • Control Housing : Or control box, is a metal or plastic box which houses the power supply, circuit boards, indicators and related controls.
  • Control Panel : The display screen (on the front of the Control Box), that provides access to the detector's operating functions, via knobs or press buttons.
  • Cross Talk : Interference between two or more metal detector's operating at the same frequency and in close proximity to each other.
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  • D

  • Depth Penetration : The metal detector's ability to Transmit an electromagnetic field into the soil and produce a target signal. Greater depth penetration from a detector means it can detect deeper targets.
  • Detectorist : A person who metal detects, whether professionally or as a hobby.
  • DISC : Short for Discrimination. See below.
  • Discrimination : Adjustable circuitry which ignores or nulls audio responses from a specific targets conductive and/or ferrous properties. Is used to eliminate audio response from trash metals.
  • Double D or 2 D : A coplanar search coil with two "D" shaped windings positioned back to back and overlapping. This type of coil has good stability in heavily mineralised ground, good depth, and good sensitivity.
  • Drift : A loss of threshold tuning stability caused by temperature change, battery condition, ground mineral content or detector design.
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  • E

  • Eddy Currents : Small circulating currents produced on the surface of metal by the detectors Transmitted electromagnetic field. These currents then generate an electromagnetic field around the target, which is then detected by the search coil Receiver windings.
  • Electromagnetic Field : An invisible force generated by electrically charged metal objects. Electromagnetic field refers to both the Transmit field from the search coil, and the Receive field from a target.
  • Elliptical Coil : A search coil that is an ellipse (oval) shape. This coil can be either Concentric or Double D type.
  • Environmental Noise : Electrical signals or noise that interferes with a detectors operation. Comes from power lines, underground cables, other detectors and electrical signals from some thunderstorms.
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  • F

  • Faint Signal : A sound characteristic heard when a target is either very small or deeply buried.
  • Falsing : Or False Signal, An erroneous signal created by the detector responding to electrical noise, ground noise, bumping or highly mineralised hot rocks. Also see Back-Reading.
  • Ferrous : Descriptive of any object or target that contains iron and therefore attracted to a magnet. Most ferrous objects are deemed as junk targets, however some can be valuable relics.
  • Frequency : The number of complete alternating current cycles produced by the Transmit search coil per second :-
    1 time per second = 1 Hz.
    1000 times per second (or 1000Hz) = 1 kHz.
    1,000,000 times per second (or 1000kHz) = 1 MHz.
      VLF Very Low Frequency = 3 to 30 kHz
      LF Low Frequency = 30 to 300 kHz
      MF Medium Frequency = 300 kHz to 3 MHz
      HF High Frequency = 3 to 30 MHz
      VHF Very High Frequency = 30 to 300 MHz
  • Frequency Shift : A feature which suppresses the audio interference (cross-talk) between two metal detectors operating at the same frequencies in close proximity to each other.
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  • G

  • Ground Balance (GB) : A state of operation where the metal detector removes the ground noise produced by the ground mineralisation from different ground/soil types. This enables clearer target signals.
      GB - Factory Preset : The Ground Balance setting is pre-set at the factory to optimize operation over an average range of non-conductive soils. The operator is unable to make adjustments to this setting.
      GB - Manual : The operator carries out the Ground Balance procedure manually, adjusting settings to personal preference.
      GB - Auto : The detector determines the best Ground Balance setting for the current ground mineralisation. Quicker and more accurate than Manual Ground Balancing.
      GB - Tracking : The detector continuously senses any change in the ground mineral content and automatically re-adjusts the Ground Balance setting while in operation. Also known as Ground Tracking.
  • Ground Mineralisation : The natural occurrence of minerals in the ground that can produce Ground Noise or false signals. There are Two main types of Ground Mineralisation. The first, (Iron particle Mineralisation) can cause the ground to become magnetic. The second, (Salt Mineralisation), can cause the ground to be conductive. Both types can affect a detectors performance if it has not been Ground Balanced appropriately.
  • Ground Noise : False signals that occur when a detector that has not been ground balanced correctly is used over mineralised ground.
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  • H

  • Halo Effect : When a metal object has been in the ground for a long time it slowly begins to oxidise into the soil directly surrounding it. This soil creates a detectable field (Halo) and can trick the detector into signalling a larger target than is actually there. Digging into the soil can instantly break the Halo and cause the signal to disappear.
  • Head : See Coil.
  • Hz or Hertz : Cycles per second. 1 cycle per second = 1 Hz, 100 cycles per second = 100 Hz : 1000 Hz = 1 kHz : 1,000 kHz (1,000,000 Hz) = 1 MHz. Also see Frequency.
  • Hip Mount : See Body Mount.
  • Hoard : A collection of coins and/or valuables that have been intentionally buried or secretly hidden. Also known as Cache.
  • Hot Rock : A rock which is highly mineralised compared to the ground surrounding it. A highly mineralised rock in mildly mineralised ground is a Hot Rock, whereas a highly mineralised rock on highly mineralised ground would NOT be classed as a Hot Rock.
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  • J

  • Junk : or Trash. An unwanted/worthless target or find i.e. ring-pull, nail, foil, etc.
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  • K

  • kHz or Kilohertz : 1000 cycles per second (1000 Hz) = 1 kHz.
    1000 kHz = 1 MHz. Also see Frequency.
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  • L

  • Lithium-ion Battery (Li-Ion) : A type of rechargeable battery that is lighter and has a low self discharge rate compared to other rechargeable batteries like - Nickel Metal Hydride (NiMH), Nickel Cadmium (NiCd) and Sealed Acid (SLA).
  • Loop : See Coil.
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  • M

  • Matrix : Refers to the total ground area penetrated by the coils Transmitted electromagnetic field. This ground area volumn may contain varying amounts and combinations of minerals, metals, salts and moisture.
  • MHz or Megahertz : 1,000,000 cycles per second (1000 kHz) = 1 MHz. Also see Frequency.
  • Metal : Metallic substances such as iron, foil, nickel, aluminum, gold, brass, lead, copper, silver, etc.
  • Mineralised Ground : Any soil that contains conductive or non-conductive components. Also see Ground Mineralisation.
  • Mode : A condition of operation, selected by the operator, for specific desired function(s).
  • Multi-Frequency : A metal detector that uses more than one Frequency. Most metal detectors run at a single frequency, whereas a Multi-Frequency detector can use Two or more frequencies at the same time.
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  • N

  • Narrow Response : A target that produces an audio response so short that pinpointing is almost not needed.
  • Ni-Cad or Nickel-Cadmium : A rechargeable type of battery.
  • Nighthawking : The act of metal detecting illegally. The illegal search and removal of artefacts using metal detectors without permissions from the landowner to be on the land.
  • Noise Cancel : A metal detector feature that shifts the detectors Frequency (or frequencies) to reduce the effect of Environmental Noise.
  • Non-Ferrous : Metals that do not contain iron. i.e, gold, silver, copper, etc.
  • Non-Motion : Refers to any mode of operation that does not require the search coil to be in motion to trigger target response.
  • Notch Accept : All target responses are eliminated (rejected), except those selected by the operator within the notch window.
  • Notch Discrimination : To enable or disable various metal groups selected by the operator. Enabled segments will create a signal, while disabled (Notched out) segments will be rejected i.e. rejecting nails, foil and ring pulls while accepting gold rings of the same conductivity. Can also be adjusted to reject all metal targets while accepting only a specific conductivity range.
  • Notch Reject : Operation whereby all targets within the notch range of a selected notch level will be rejected.
  • Null : The momentary drop or disappearance of the threshold sound as the search coil passes over a discriminated or rejected target.
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  • O

  • Overlap : How much of the coil on the current swing passes over the coil path of the previous swing.
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  • P

  • Phase Response : The length of time between when an eddy current is generated and the resulting secondary electromagnetic field effecting the coils Receive (RX) windings.
  • Pinpointer : Not to be confused with Pinpointing (see below). A small, handheld device for probing into the freshly dug hole or prodding into the Plug to accurately locate a Target. Uses louder Audio and/or quicker vibration the closer it gets to the target.
  • Pinpointing : Not to be confused with Pinpointer (see above). Pulling a trigger or pressing a button to narrow the Search Coil's Transmit/Receive signals to the Coils designated center. Helps to identify the exact target location and where to dig your hole.
  • Plug : The volume of Soil that is hinged back from a carefully cut hole when digging for a target. Usually One single lump of soil per hole.
  • Positive Ground : Soil which contains conductive minerals or moist salts which have a positive or upward effect on an air-tuned threshold.
  • PI or Pulse Induction : A mode of operation where the Transmit (TX) circuitry 'Pulses' an electrical current into the ground before it quickly shuts down. The eddy currents immediately dissipate from poor conductors such as wet salt sand and ground minerals, whereas metals hold eddy currents because they are better conductors. When the Receive (RX) circuit comes on, it only picks up the returning signal from metal, as the eddy currents in the ground minerals have already disappeared.
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  • Q

  • Quick Response : A quick reaction time between the detector sensing the target and the audio/visual indication to the operator.
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  • R

  • Receive (RX) : A returning signal from the ground that is picked up by the coil. The process of collecting a signal or magnetic field by the Search Coil. Also see Transmit (TX).
  • Rejection : An indication of non-acceptance of a target by a null in threshold or broken sound while in a discriminate mode.
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  • S

  • Scrubbing : The search coil is pressed and held in contact with the ground while searching to maintain even audio threshold. With newer detectors, this technique is used to gain depth.
  • Search Coil : See Coil.
  • Search Coil Cable : An electrostatically shielded cable of conductors (wires) which transport signals to and from the search coil and control housing.
  • Sensitivity : The capacity of a metal detector to perceive changes in conductivity within the detection pattern. Generally, the more sensitivity a detector can smoothly provide, the more depth it will achieve in sensing targets.
  • Signal : An audio response or visual indication alerting the operator that a target has been detected.
  • Signal Width : The total distance of ground an audio signal is sustained during search- coil travel or scan.
  • Silent Search : Refers to detectors capable of producing a target signal while operating below the threshold audio. Also called silent operation.
  • Scuff Cover : A protective cover for the search coil bottom. Also called coil cover or skid plate.
  • Stability : The ability of a metal detector to maintain manually adjusted tuning threshold under the effects of outside interference. Also see Drift.
  • Swing : Or Sweep. The motion employed in moving the search coil across the ground.
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  • T

  • Target : Refers to any metal object that causes an audio or visual response in a detector. A Target can be a good Target (coin) or a bad Target (ring-pull).
  • Target Response : See Signal.
  • Test Garden : A mapped plot of buried targets at various depths to aid in learning characteristic target responses and in comparing metal detector performances under a given ground mineral content. Also called test plot or test bed.
  • Threshold : Continuous tone that establishes a reference point for listening for Target signals. The threshold tone will disappear briefly (Null) to indicate a Discriminated target has been detected.
  • Tone ID : Circuitry producing different audio tones for each target's conductivity range, i.e., low tone for iron, high tone for coins.
  • Transmit (TX) : The signal that is sent FROM the coil into the ground. The process of sending a signal or magnetic field by the Search Coil. Also see Receive (RX).
  • Trash : or Junk. An unwanted/worthless target or find i.e. ring-pull, nail, foil, etc.
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  • V

  • Visual ID : A feature in which a visual indication is produced to help identify the target.
  • Visual Indicator : A meter or screen that relays a targets identity visually to the operator.
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  • W

  • Wide Response : A target that produces an audio signal over an area wider than the search coil diameter.
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  • Z

  • Zero Discrimination : A setting where no metals are Discriminated. All metals are detectable.
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