Glossary of Basic Metal Detecting Terms

Terminology Used in Metal Detector User Manuals & Among Metaldetectorists: from N to R


NARROW RESPONSE - An audio target signal which is not wider than the physical size of the search coil.

NEGATIVE GROUND - Non-conductive soil matrix which has a negative or nulling effect on an air tuned audio threshold.

NEUTRAL GROUND - Soil with little or no non-conductive or conductive properties.

NICAD - A class of rechargeable battery having a nickel-cadmium composition.

NiMH - A class of rechargeable batteries having a nickel-metal-hydrate composition. NiMH batteries have a longer life-span and are not affected by memory to the same degree.

NON-FERROUS - Metal types not containing iron such as gold, silver, copper, aluminum, etc. If a metal object is attracted to a magnet, it is called ferrous.

NON-MOTION - Any mode of operation which sustains target response without search coil motion.

NON-MOTION ALL-METAL - movement of search coil is not required to get an audio response from any metallic target. This mode is used for pinpointing targets.

NOTCH ACCEPT - A basic notch filter discrimination mode which eliminates all responses except those whose conductive properties fall within the range of the notch width.

NOTCH DISCRIMINATION - it allows to select which of the conductivity segments in the discrimination scale are active or disabled. If a segment is "notched out," then metals within that range of conductivity will be masked and will not produce a signal.

NOTCH FILTER DISCRIMINATION - Specialized discrimination circuitry which selectively accepts or rejects a narrow conductive range of targets inside or outside normal discrimination settings, i.e. accepting nickel coins while rejecting targets higher in conductivity such as pull-tabs.

NOTCH LEVEL - The control used to position the notch width or "window" within the range of metallic conductivities.

NOTCH REJECT - A basic notch filter discrimination mode which rejects only those targets whose conductivities fall within the range of the notch width.

NOTCH WIDTH - A preset or adjustable range of conductivity positioned by the notch level setting - also known as NOTCH WINDOW.

NULL - A momentary disappearance of threshold audio as the search coil passes over a rejected target or a hot rock located with a ground balanced mode.

NUMISMATIST - A person specializing in the study and collection of coins, tokens, and currency.



OSCILLATOR - A metal detector circuit component which sends a specific current frequency generation to the transmit windings of the search coil to produce an electromagnetic field.

OVERLAP - The amount of scan advance not greater than the physical size of the search coil.

OVERSHOOT - False signals produced by an auto-tuned non-motion discriminate mode as the search coil passes too quickly past a rejected target. Excessive audio restoration by automatic re-tuning produces these false signals outside the target response periphery.


PHASE RESPONSE - The duration of time between target surface eddy current generation and resultant secondary electromagnetic field effect on the search coil's receive windings. Also called phase lag or phase angle and is directly related to target conductivity.

PINPOINTING - The act of aligning the center of target response width to the designated search coil center for accurate location and careful recovery.

PLUGGING - A method of target recovery by which a plug of soil is carefully cut and folded back to expose deeper targets which cannot be successfully recovered with other methods.

POSITIVE GROUND - Soil containing conductive minerals or wet salts that affect an air tuned audio threshold.

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

PRESET FACTORY PROGRAMS - A number of search programs such as "COINS", "COINS & JEWELRY", "RELICS", "BEACH", etc. that are designed and incorporated into the metal detector's memory to make it easy for a beginner to start using the detector right after taking it out of a box.

PRESET MARKINGS - Metal detector control panel markings which have been highlighted by the manufacturer as a guide to setting up the detector for average operating conditions.

PI - An abbreviation for Pulse Induction circuit technology. This type detector ignores both non-conductive and conductive minerals simultaneously by pulsing the receiver amplifier off before the response from wetted salts and iron oxides can reach the search coil winding. The search coil of the PI detector consists of only one wire loop which is both transmitter and receiver at the same time. PI detectors are capable of extreme depth but are currently inept at rejecting undesired targets, i.e. they can not operate in Discrimination mode.

PUMPING MODE - a semi-automatic or manual process which allows an operator to adjust the metal detector's ground balance in a zone that has been determined to be representative of the mean level of ground mineralization in the area being searched. An operator lifts a search coil up to 6" (15cm) and lowers it down to the ground a few times until a displayed confirmation received or no audio responses are heard during manual adjustment of the ground balance.


QUICK RESPONSE - The measure of time it takes between metal sensing and full audio/visual response. Generally associated with all frequencies of TR detectors.


RECEIVE WINDING - The coil(s) of wire inside the search coil housing whose function is to accept the secondary electromagnetic field generated on a target's surface by eddy currents.

RECOVERY TIME (also called REACTIVITY or RECOVERY SPEED) - The duration of time it takes a metal detector to respond to the next target after responding to the previous. Most metal detectors have slow recovery speeds (from 1 to 1.5) and often are unable to respond to all targets in close proximity, or targets near iron nails, when a lot of Discrimination is used. Metal detectors with high REACTIVITY levels (at 2 and higher) are the best "coin shooters".

REJECTION - Non-acceptance of a target when operating in the discriminate mode indicated by a null in threshold audio or no change in silent operation.

RETUNING - The act of manually restoring threshold audio by means of an external switch, (see AUTO-TUNE).

Rx (Receive) refers to the response, or electromagnetic field, which is received back by the coil and is used by the control box circuitry to process it accordingly.

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