Glossary Of Terms For Metal Detector Users

Glossary of DFX and General Metal Detecting Terms

A.C. SENSITIVITY: A DFX menu setting that determines the discrimination sensitivity. Allows selection of the degree to which the detector will respond to signals while in a discriminating mode (one where the loop coil must be moved).

A.G.B.: Automatic Ground Balance. See GROUND BALANCE - Self Adjusting and AUTOTRAC (for DFX).

AIR TEST: A procedure performed by placing a metal detector on a non-conductive surface and passing various sized metal samples beneath the coil to check the detector's features and target response. This test is NEVER an accurate indicator of ground depth penetration capability nor is it ever meant to be. See BENCH TEST.

ALKALINE: A type of battery able to sustain longer periods of current drain with greater storage life when compared to the standard carbon-zinc type or the nickel cadmium (NiCa).

ALL-METAL: Any operating mode or control setting that allows total acceptance of any type of metal targets. Usually associated with the Ground Balance mode. This is the usual setting for hand probes.

ANTENNAE: See SEARCHCOIL.

AUDIO DISC: Menu setting that allows detector to discriminate “trash” sounds by silencing or breaking them off and giving “valuable” sounds a smooth and solid tone, if ON.

AUDIO FREQUENCY: See TONE.

AUDIO ID: Circuitry that produces different audio tones (pitch) for different targets’ conductivity. See also TONE ID.

AUDIO RESPONSE: See TARGET RESPONSE.

AUDIO THRESHOLD: Menu setting that sets the desired loudness of the background hum (threshold).

AUTO TUNE: Circuitry that continuously retunes the detector's threshold to the initial manually tuned audio level. The retuning rate following target rejection or drift can be preset or variable.

AUTOTRAC: A DFX menu setting that automatically adjust the Ground Balance while searching when turned ON. OFF keeps the same original ground balance unless re-balanced manually.

AUTOTRAC OFFSET: A DFX menu offset adjustment that allows the AGB to be set either slightly more positive or negative than would normally register as a perfect ground balance. Used by the “pros” to enhance signal of tiny metals (+) such as gold nuggets or eliminate “hot rocks” (-) in difficult ground.

AUTOTRAC SPEED: A DFX menu setting that dictates when the AGB automatically adjusts the detector’s ground balance. Should occur every 3-5 sweeps. See GROUND BALANCE – Self Adjusting.

AUTOTRAC VIEW: A DFX menu setting that, when ON, allows operator to see when the detector automatically ground balances (autotrac) by displaying the word “TRACK” in the right side of the display screen. Used when experimenting with different Trac Speeds to determine how often detector adjusts.

BACKLIGHT: A DFX menu setting that lightens the display window in dark conditions. 0 is OFF. ON levels are 1-6.

BACK READING: A false signal, when operating in the discriminate mode, caused by a rejected target coming within one inch of or contacting the searchcoil bottom.

BACK SHOOT: Caused by slightly tipping the outside edge of the coil up at the end of a ground scan (detuning the coil). Often users mistake this for a defect in the detector or a falsing signal.

BENCH TEST: An air test to determine at what approximate discriminate settings various metal samples are rejected or accepted. The test is conducted in a non-metallic area.

BLACK SAND: One of the most extreme components of nonconductive, negative ground minerals. Also called magnetite (Fe30) or magnetic iron oxide. Often associated with the location of gold flake and nugget deposits.

BLOCK EDIT: A DFX menu setting that speeds up Disc Edit changes by dragging blocks (or groups) of Accept or Reject VDI number choices with arrow controls (scrolling) rather than entering each VDI number separately. See DISC EDIT.

BODY-MOUNT: A configuration whereby the control housing is separated from the control shaft and fastened to the operator's body lessening arm fatigue and expanding usability for shallow water hunting. Also known as Hip mount.

BOTTLE CAP REJECT: A DFX menu setting that determines how strongly the detector will reject or “break up” audibly on iron targets. Allows detector to better recognize iron in difficult (often trashy) ground. Higher settings give more iron rejection. Nickels tend to sound better at lower settings.

CACHE: Any intentionally hidden, stored, stashed, buried or secret hoard of equipment, supplies or valuables.

CARBON-ZINC: The most common standard dry cell battery type.

COARSE G.E.B.: A DFX menu setting that allows viewing of current AGB and/or manual overriding of the AGB. Used for controlled detector reactions to specific minerals. Must turn Autotrac OFF when using. See FINE G.E.B.

COIL: See Searchcoil.

COIL COVER: A tight fitting plastic protective cover for the searchcoil bottom. Also called scuff cover or skid plate.

COIN DEPTH INDICATOR: A visual indicator used in conjunction with calibrated circuitry to indicate depth of buried coins in inches.

COIN SHOOTING: A common or slang term for metal detecting coins only.

CONCENTRIC: A searchcoil configuration using one or more transmit and one receive windings having unequal diameters aligned on a common center; most recently arranged on the same plane and called Coplanar Concentric.

CONDUCTIVE SALTS: One of the major mineral types that make up the positive ground matrix. Wet, ocean salt/sand produces a positive rise or metallic type response on an air-tuned threshold.

CONDUCTIVITY: The measure of a metal target's ability to allow the generation of eddy currents on its surface.

CONTROL HOUSING: A metal or plastic box that holds circuit boards, indicators, meter, controls and power supply.

CONVERTIBLE / COMBINATION: A metal detector configuration allowing versatility in operator handling (i.e. hand held to body/hip mount).

COPLANER: Any searchcoil configuration in which transmit and receive windings occupy the same level or plane.

CRYSTAL CONTOLLED OSCILLATOR (CCO): A transmit oscillator employing a crystal to maintain a stable output frequency.

D.C. PHASE: A DFX menu setting that is used to measure the ground mineralization and a Phase (reference) number of a specific target while pinpointing. This is useful to the “pros” that use the COARSE and FINE G.E.B settings. By measuring the ground and noting various target reference numbers optimum settings might be re-entered and used in a different area with similar conditions without multiple adjustments or experimenting being required.

D.C. SENSITIVITY: A DFX menu setting that sets detector sensitivity (degree to which it will respond to any signal). Allows selection of the degree to which the detector will respond to any signals while in a non-discriminate (All-Metal, non-motion) mode.

DEPTH / DEPTH PENETRATION: The greatest measure (usually in inches) of a metal detector's ability to transmit an electromagnetic field into the ground and produce a target signal.

DETECTION PATTERN: The densest or strongest region of the searchcoil's electromagnetic field where detection occurs. Its shape is balloon and changes in size directly proportional to target surface area.

DE-TUNING: A method of manually or automatically desensitizing a metal detector so that it may locate the center of a target. Accomplished by adjusting the audio threshold into the null, or less sensitivity, tuning zone. This narrows a target signal width manually for precise pinpointing by retuning the audio threshold over the target response area (e.g. releasing and pressing the pinpoint control one or more times while the coil is over the target). See PINPOINTING.

DISC: See DISCRIMINATION.

DISCRIMINATION: Adjustable control circuitry or methods which ignores (or nulls) audio responses from a specific conductivity/phase range allowing positive responses to be heard from metals higher in conductivity above the discriminate control setting. Designed primarily to eliminate audio/visual responses from trash (lower conductive) metals. Discrimination has greater impact on how a detector operates than any other feature. See also Motion Discriminator.

DISC EDIT: A DFX menu setting that allows the changing of target reference (VDI) numbers, one at a time, as to whether they are either Accepted (detected) or Rejected (discriminated out) within any given program used. See BLOCK EDIT.

DOUBLE BLIP: An audio signal characteristic common to elongated ferrous targets such as nails or coins lying close to the surface detected in the All-Metal no-motion mode.

DOUBLE D, 2D or DD: See WIDE SCAN.

DRIFT: A loss of threshold tuning stability caused by temperature change, time, battery condition, ground mineral content or detector design.

EDDY CURRENTS: Small circulating currents of electricity produced on the surface of metal by a transmitted electromagnetic field. These currents then produce a secondary electromagnetic field that can be detected by the search coil receiver (resulting in inductive imbalance between the windings).

ELECTROMAGNETIC FIELD: An invisible force extending from top and bottom of the searchcoil created by the flow of alternating oscillator frequency current around the transmit winding. See also DETECTION PATTERN.

ELECTRONIC PINPOINTING: An automated detuning feature that narrows signal response for the purpose of target pinpointing. Can also refer to the use of palm held electronic probes.

ELLIPTICAL COIL: A searchcoil with an ellipse (extended oval) shape. This coil can be either concentric or wide scan type.

FADE: A DFX menu setting that determines how quickly target bars fade (clear) from display after each target hit. Set to see target information but not still be there when another target is hit during a different coil sweep.

FAINT SIGNAL: A barely produced audio response. A sound characteristic of targets that are sometimes deeply buried or very small in size.

FALSE SIGNAL / FALSING: An erroneous signal created by over shoot, back shoot, uneven ground, ground voids or highly mineralized hot rocks. When in the discriminate mode, a signal caused by a rejected target coming within one inch of or contacting the coil bottom. See also BACK READING.

FARADAY-SHIELD: A metal foil wrapping of the searchcoil windings or metallically painted search coil housing interior for the purpose of eliminating electrostatic interference caused by wet vegetation.

FERROUS: Descriptive of any iron or iron bearing material.

FERROUS OXIDE: An oxidized particle of iron, which generally becomes nonconductive and makes up the natural negative ground mineral matrix. Hematite, which is also iron oxide (Fe2 03), will respond as positive or metallic. See also Black Sand.

FINE G.E.B.: A DFX menu setting that allows smaller adjustments of the current Coarse G.E.B. setting to determine an actual ground rejection level. Must turn Autotrac OFF when using. See COARSE G.E.B.

FREQUENCY: The number of complete alternating current cycles (on and then off = 1 cycle) produced by the transmit oscillator per second. Frequency is measured in kHz or cycles per second. (VLF) Very Low Frequency = 3 to 30 kHz (LF) Low Frequency = 30 to 300 kHz (MF) Medium Frequency = 300 to 3000 kHz (HF) High Frequency = 3 to 30 MHz. (NOTE: Most metal detectors are VLF)

FREQUENCY SHIFT: A feature that suppresses the audio interference (cross-talk) between two detectors using identical transmitting frequencies in close proximity (approximately 20 feet or less).

GAIN: See PREAMP GAIN or SENSITIVITY.

GRAPH ACCUMULATE: A DFX menu setting that, when ON, collects the VDI graph bars instead of clearing them after each coil sweep. It combines graphic display information over multiple coil passes over a target. Should be used with FADE to prevent display from filling up.

GRAPH AVERAGING: A DFX menu setting that averages all target hits in several sweeps to determine a target ID. It emphasizes the most common or predominant display indicators to show the most likely target. Works more efficiently if used in conjunction with GRAPH ACCUMULATE and FADE.

GROUND BALANCE: A highly misunderstood, yet important, aspect of metal detecting. It’s the operation of special detector circuitry that can ignore the “masking effect” that iron (ferrous) minerals can have over metal targets in the ground. It’s the detectors ability to ignore these disruptive effects; similar to fog lights penetrating heavy fog.

GROUND BALANCE - Factory Preset: A feature that eliminates the manual ground balance control and its adjustment from the operator's setup procedure. The factory, to optimize operation over an average range of nonconductive soils, performs this adjustment internally.

GROUND BALANCE - Manually Adjusted: A feature requiring a manual control adjustment procedure to neutralize the effects of negative minerals in the search matrix.

GROUND BALANCE - Self Adjusting: A feature which senses change in ground mineral content and continuously readjusts the ground balance while in operation. Sometimes called Ground Tracking or Automatic Ground Balance (AGB). See AUTOTRAC (for the DFX).

GROUND FILTER: Complex circuitry found in motion-type detectors which separates mineral signals from metal signals allowing it to be further processed by the discrimination circuitry. Used to distinguish between ground, trash and valued targets. The fewer filters there are, the quicker the detector responds. But detection depth is lost in mineralized ground with fewer filters. More filters give more depth and better audio discrimination for targets located. But response is correspondently slower.

GROUND FILTERING (High Pass Filters or Differentiators): A DFX menu setting that allows a choice of how many High Pass filters will be used while searching. Needs to be closely balanced with SWEEP SPEED and RECOVERY SPEED for optimum performance.

GROUND FISHING: A slang term for metal detecting.

HALO: A geological soil condition manifesting an effect known as “Metallurgical Phenomenon”. A metallic halo is generated over time by the combination of acids and water in the soil leaching minute particles off a metal target into the surrounding soil.

HAND HELD: A metal detector configuration whereby the operator holds a shaft or handle that supports the searchcoil and control housing. Also called a pole mount. See BODY MOUNT for contrast.

HEAD: See SEARCHCOIL.

Hz or HERTZ: Cycles per second. See also FREQUENCY.

HIP MOUNT: See BODY MOUNT.

HOT ROCK: A rock that contains a higher or significantly different concentration of nonconductive ground minerals than the surrounding ground to which the detector is balanced. A metallic (positive/conductive) response will be heard in the motion and non-motion modes and a null or negative drop in threshold is heard in the All-Metal ground balanced mode over these rocks. Ironstone is a typical hot rock. VDI number response is +95.

HOT ROCK REJECT: A DFX menu setting that allows for varying degrees of detector response rather than a typical total Accept or total Reject

ICON: A graphic representation of metal targets on a display, e.g. picture of a Nail, Foil, Pull Tab, Screw Cap, Penny or Dime.

ICONS: A DFX menu setting that, when ON, allows you to look at selected Icons for possible targets detected. Many turn this setting OFF, once they feel familiar with target VDI numbers. Doing so tends to limit visual distraction and increase the overall display response speed.

INDUCTANCE: An object that conducts electricity easily (is inductive) is slow to react to changes in the current. You can think of inductance as a deep river: Change the amount of water flowing into the river and it takes some time before you see a difference.

IRON STONE: A rock heavily laced with iron.

ISOLATOR: A nonmetal stem that attaches the searchcoil to the control shaft eliminating metallic interference in the detection pattern. On some detectors, the entire lower shaft is made of a nonmetal substance.

kHz or KILOHERTZ: 1 kHz = 1000 cycles per second. See also FREQUENCY.

LCD or LIQUID CRYSTAL DISPLAY: Used on a metal detector as a graphic visual (digital) indicator. Serves the same as a meter/needle (analog) indicator.

LEARN ACCEPT/REJECT: Two separate DFX menu settings that, when ON, allows targets swept beneath the coil to be Accepted or Rejected by the VDI number the detector then reads. ACCEPT is very useful when searching for a specific target only, such as one of a pair of earrings. REJECT is used when a specific trash target needs to be discriminated out. These settings MUST be turned OFF after learning a target or detector will continue to Accept/Reject EVERY single target it encounters!

LIGHT EMITTING DIODE or LED: A semiconductor that produces an illuminated visual response, often on a display.

LOOP: See SEARCHCOIL.

MATRIX: Refers to the total volume of ground penetrated by the transmitted electromagnetic field-which may contain varying amounts and combinations of minerals, metals, salts and moisture.

MD’er / MD’ing: Recognized word contractions for Metal Detectorist or Metal Detecting.

MENU: A Series of listings and/or prompts on a visual display designed to aid the operator in feature or program selection.

METAL: Metallic substances such as iron, foil, nickel, aluminum, gold, brass, lead, copper, silver, etc.

METAL DETECTORIST: A person operating a metal detector in the field. Preferred by many over Treasure Hunter, Th’er, Ground Fisher, Sand Crabber or Beeper Swinger. Contracts to MD’er.

METER: A detector component that provides visual information to aid in target identification. Meters feature either an LCD (digital) or needle (analog) indicator which may display intensity of signal, target depth, target identification, type of metal, or battery condition.

MICROPROCESSOR: An electronic component that can be programmed to perform certain electronic functions.

MINERAL-FREE DISCRIMINATOR: Any metal detector that can reject or ignore trash metals while simultaneously balancing ground mineralization.

MINERALIZATION: Conductive or nonconductive components found in the soil.

MINERALIZED GROUND: Any soil that contains conductive or nonconductive components.

MIXED MODE: A DFX menu setting that employs a hybrid All-Metal (DC non-motion, non-discriminate, detect everything) mode to work simultaneously with a discriminate (AC motion discrimination) mode at the same time. Used by “pros” for extra depth. When used with V.C.O. and TONE ID by experienced detectors many desirable targets can be found in areas “picked clean” by others before them.

MODE: A condition of operation, selected by the operator, for specific desired functions (e.g. All-Metal or Coin-Jewelry).

MODULATION: A DFX menu setting that produces (when ON in motion modes) different volume levels based on target depth. Can save time in pinpointing for depth. Not a good setting for those with hearing problems.

MOTION DISCRIMINATOR: A detector type that requires searchcoil motion to activate its simultaneous ground balance and discriminate functions. See also MINERAL-FREE DISCRIMINATOR and VLF/TR.

MOTION MODE: Any mode that requires searchcoil loop movement to respond to metals.

NARROW (or TIGHT) RESPONSE: A target that produces an audio response so short that pinpointing is almost not needed.

NEGATIVE GROUND: Soil that contains non-conductive minerals that have a negative or nulling effect on an air-tuned threshold.

NEUTRAL GROUND: Soil that has no non-conductive nor any conductive mineral properties. Lacks any detectable mineralization whatsoever.

NICAD, NiCa, Ni-Cad or Nickel-Cadmium: A rechargeable type of battery cell.

NON-FERROUS: Metals not made of iron. Metals of the precious class (i.e., gold, silver, copper, etc.)

NO-MOTION MODE: Refers to any mode of operation that does not require searchcoil motion to trigger target response. Also called non-motion.

NOTCH, NOTCH ACCEPT or ACCEPT: Operation whereby all target responses are "tuned-out" except those the instrument is adjusted to accept in the desired notch "window."

NOTCH DISCRIMINATION: Filtering circuitry that allows a "window" of desirable targets to be accepted within the entire rejection range of unaccepted targets, i.e. rejecting nails, foil and pull tabs while accepting nickels and gold rings of the same conductivity. This circuitry can also be adjusted to reject All-Metal targets while accepting only a specific conductivity range.

NOTCH LEVEL: A control used to select the target level or target conductivity that the notch filter will act upon.

NOTCH REJECT or REJECT: Operation whereby all targets within the notch width at a chosen notch level will be discriminated or "tuned-out."

NOTCH WIDTH: A finite discrimination range of target conductivities (window) at the chosen notch level.

NULL: The zone just below audible threshold in metal detector tuning. This also refers to the momentary drop or quiet response of threshold sound as the searchcoil passes over a discriminated or rejected target.

OVERLAP: The measure of searchcoil swing advance not greater than the searchcoil's physical diameter. Also refers to the technique of maximum ground coverage while coil sweeping.

OVERLOAD: A situation in which too much information is coming too quickly for circuitry to discern and react. Can occur when sensitivity settings are too high for ground conditions or detector settings as they are. Can also be caused by targets being too large (buried car), too close (base of steel light pole) or too conductive (high power lines or another detector).

OVERSHOOT: A common false signal heard as the searchcoil passes over a rejected target when using a no-motion All-Metal mode in conjunction with automatic retuning. Excessive tuning restoration pushes the audio above threshold level creating a positive response at the edges of target detection periphery.

PHASE / PHASE RESPONSE: The length of time between eddy current generation sustained on a metal's surface from the searchcoil transmitter coil and the resultant secondary electromagnetic field effect on the searchcoil's receiver coil. Related to target’s conductivity.

PHASE SHIFTING: The difference in timing between the transmitter coil's frequency and the frequency of the target object. Phase shift provides VLF metal detectors with a capability called discrimination. Since most metals vary in both inductance and resistance, a VLF metal detector examines the amount of phase shift and compares it with the average for a particular type of metal.

PINPOINTING: Finding the exact center of a target location with respect to a searchcoil's designated center. Accomplished by interpreting the centers of audio response width in perpendicular directions or scans. Can also refer to the use of a hand held probe. See DETUNING.

POSITIVE GROUND: Soil that contains conductive minerals or moist salts that have a positive or upward effect on an air-tuned threshold. Can create difficult searching for some metal detectors.

PULSE INDUCTION or PI: A mode of operation where the transmitter coil circuit sends short powerful bursts (pulses) of current into the ground just before it quickly shuts down. Each pulse generates a brief magnetic field. When the pulse ends, the magnetic field reverses polarity and collapses very suddenly, resulting in a sharp electrical spike. This spike lasts a few microseconds (millionths of a second) and causes another current to run through the coil. This current is called the reflected pulse and is extremely short, lasting only about 30 microseconds. The eddy currents dissipate immediately from poor conductors such as wet salt sand and ground minerals. Precious metals hold eddy currents because they are better conductors. When the receiver circuit quickly comes back on, it picks up the returning signal from metal; the eddy currents in the ground minerals have already disappeared in this short time. Unlike VLF, PI detectors may use a single coil as both transmitter and receiver, or they may have two or even three coils working together. PI detectors have poor discrimination but work better than VLF detectors in salt-water and can find very deep metals better.

PREAMP GAIN (Signal Balance): Similar to a Sensitivity Control, it’s a DFX menu setting that adjusts the detector’s sensitivity to the ground or target. Used to promote stability and performance. Higher settings affect both the A.C. (motion, discriminating) and D.C. (All-Metal, non-motion) SENSITIVITY. For maximum depth tune to highest setting possible without causing OVERLOAD or unstable operation. Using MIXED MODE or AUDIO DISC OFF may not allow as high a setting as otherwise. DFX should be re-ground balanced after any Preamp Gain change.

PROSPECTING: Searching for valuable minerals, such as gold nuggets.

QUICK RESPONSE: A short time period between metal target sensing and a peak audio/visual indicator appearing. Usually associated with all frequency ranges of TR detectors. See RECOVERY SPEED.

RATCHET PINPOINTING: A DFX menu setting that allows automatic detuning of the loop while pinpointing to help find center location of a target. Usually trigger activated.

RECEIVER COIL: On a VLF metal detector this is the inner coil loop contains another coil of wire. This wire acts as an antenna to pick up and amplify frequencies coming from target objects in the ground.

RECOVERY SPEED: A DFX menu setting that speeds up a targets normal response time, thus several targets close together can be detected separately. Use faster speeds for trash areas (but you’ll lose depth). Fast speeds should NOT be used unless necessary. Use slower speeds for less trashy areas to improve detection of deep targets and get better discrimination of shallow targets. Should always be used in a tri-setting coordination with SWEEP SPEED and especially GROUND FILTERING settings. See SWEEP SPEED and GROUND FILTERING.

REJECT / REJECTION: An indication of target nonacceptance by a null (silence) in threshold or broken sound while operating in a discriminate mode.

RELIC HUNTING: Searching for items of historical value, such as weapons, ammunition, tools, or buttons used in a war.

RESISTANCE: An object that does not conduct electricity easily (resistive) is quick to react to changes in the current. Using a water analogy, resistance would be a small, shallow stream: Change the amount of water flowing into the stream and you notice a drop in the water level very quickly. See INDUCTANCE for contrast.

RF-TWO BOX: A radio frequency detector having its own transmit and receive windings separate and in an orthogonal configuration. This detector is capable of deep large object detection while naturally ignoring small targets such as nails and individual coins. Not common or even known to most hobbyists.

S.A.T. SPEED: A DFX menu setting that allows for a self-adjusting threshold (auto-tune). Works in the no discriminate or mixed-mode only. Has no effect in the discriminate (coil in motion) mode.

SCAN: 1) The effective searchcoil detection width or 2) The back and forth passing movement of the searchcoil over the ground.

SCRUBBING: The searchcoil is pressed and held in contact with the ground while searching to maintain even audio threshold. With newer detectors, this technique is often used to gain depth (especially on grass, leaves or pine straw).

SEARCHCOIL: A circular (or other shaped) plastic housing containing single or multiple transmit and receive windings (wire coils) in a specific configuration. A searchcoil emits and receives signals from the ground and metal targets. Also called a coil, loop, head or antennae.

SEARCH COIL CABLE: An electro statically shielded cable of conductors (wires) that convey signals to and from the searchcoil and control housing.

SENSITIVITY: 1) The intensity of the signal received from the search coil. 2) The measure or capacity of a metal detector to perceive changes in conductivity within the projected detection pattern. 3) The changing of control settings to make the searchcoil more receptive to a chosen target. 4) Also the knob that controls the coil sensitivity. Generally, the more sensitivity a detector can smoothly provide, the more depth it will achieve in sensing targets.

SIGNAL: An audio response or visual (digital or analog) display alerting the operator that a target has been detected.

SIGNAL BALANCE: A setting that selects the intensity of the signal received from the search coil. See PREAMP GAIN.

SIGNAL WIDTH: The total distance of ground an audio signal is sustained during searchcoil travel or scans.

SILENT SEARCH: Refers to detectors capable of producing a target signal while operating below the threshold audio. Also called Silent Operation. The detector is silent (not even threshold) until a target is detected.

SLOW MOTION: A description of searchcoil speed required to operate the motion discriminate mode.

STABILITY: The ability of a metal detector to maintain a smooth predictable performance. Also, the ability to maintain manually adjusted tuning threshold despite the effects of outside interference. See also DRIFT.

SURFACE AREA: Refers to the area of a target closest to the searchcoil where eddy current generation can take place.

SURFACE MOUNT: The art of mounting electronic components on the surface of a printed circuit board rather than using the "through board" method. This allows more technology in a much smaller space with much higher tolerances.

SWEEP: The motion employed in moving the searchcoil across the ground. See SCAN (def. 2).

SWEEP SPEED: A DFX menu setting that adjusts the width of the target signal to be analyzed. In competition or in open non-trashy areas a higher speed (narrower sample window) is desired while in older or trashy areas a slower speed (wider sample window) is needed for a more thorough and accurate search. Sweep speed is highly interactive and interdependent upon RECOVERY SPEED and GROUND FILTERING settings. All must be coordinated for best results.

TARGET: Refers to any object that causes an audio or visual response in a detector.

TARGET MASKING: When large sized or high concentrations of trash metals drive the threshold into the null zone suppressing weaker, positive responses from deeper or smaller targets.

TARGET RESPONSE: See SIGNAL.

TARGET VOLUME: A knob or menu setting that provides the desired loudness of a target response.

TEN-TURN: A control that can be manually rotated ten times to cover the full electrical range of the function. Usually associated with tuning or ground balance function. Similar to a fine tune adjustment on an FM radio.

TEST GARDEN: A mapped plot of buried targets intentionally planted 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. (NOTE: Due to an effect known as “Metallurgical Phenomenon” or “halo” newly buried coins are difficult to detect. If you bury them deep don’t expect to locate them for a while until they have had time to react with the acids in the soil and form an electromagnetic halo.)

TH'er, TH'ing: Contractions for treasure hunter and treasure hunting. Also known as MD’er or MD’ing. See TREASURE HUNTING.

THRESHOLD: Arguably, this is the most misunderstood term in metal detecting. It’s the continuous tone, or background hum, that 1) establishes a reference point for tuning the detector so it can be ground balanced, 2) sets the audio level for pinpointing targets and 3) determines the minimum (lowest) sound level for deep targets in the discriminate mode.

TID: Target Identifier Display. See VISUAL ID.

TONE (AUDIO FREQUENCY): Menu setting that sets the tone (pitch) of the threshold (background hum).

TONE ID: A DFX menu setting that can help in target I.D. by assigning each VDI # a distinct tone (pitch). For example: low tones and #’s for iron and junk, medium tones for nickels or pull-tabs, and high tones for silver and coins.

TRAC INHIBIT: A DFX menu setting that prevents Autotrac ground tracking/balancing (or AGB) when over a possible target during detection. Helps prevent the masking or deletion of an actual target due to balancing of metal corrosion around a target. Should be OFF if looking for targets that don’t corrode such as gold prospecting.

TRANSMITTER COIL: On a VLF metal detector this is the outer coil loop of the searchcoil. Within it is a coil of wire. Electricity is sent along this wire, first in one direction and then in the other, thousands of times each second (measured as kHz) to produce an electromagnetic eddy on metallic targets in the soil. See FREQUENCY.

TRANSMITTER-RECEIVER / TR: Term describing method of operation of early or primitive detectors. Some manufacturers still produce this type of detector. Electromagnetic field distortion caused by mineralized ground interferes with depth penetration as this type of detector does not ground compensate. It does balance conductive salt-water effects so; it is primarily used in salt water and on low mineral salt-water beaches or low mineral inland locations.

TREASURE HUNTING: A sub-group of the broader metal detecting hobby, it’s using historical, biographical, geographical, topographical, geological and even genealogical research to locate and then (utilizing a metal detector) find: caches of gold, silver or anything else thought to have been hidden or lost.

V.C.O.: A DFX menu setting where a Voltage Controlled Oscillator can make a target’s audio response increase in volume and pitch as the coil approaches target’s center. Is used in All-Metal or Pinpointing (squeezed trigger) modes.

VIEWING ANGLE: A DFX menu setting that makes the display easier to see at different temperatures.

V.D.I.: Visual Display Image. Whites Spectrum detector graphic showing numbers, graphs or Icons. See VISUAL ID.

V.D.I. SENSITIVITY: A DFX menu setting that determines how intense the graphic response to a target will be. Lower setting offers fewer but more reliable displays, but some deep targets may not give a response. Higher settings give more display indications but aren’t as reliable. Any level setting over 85 will display as a three (instead of two) digit number for more resolution. This is helpful in distinguishing similar targets like nickels, rings and pull tabs.

VISUAL DISC: A DFX menu setting that, when ON, prevents Rejected VDI numbers and their associated Icons from being displayed. When OFF, all VDI numbers are displayed when they are targeted. Useful in clearing display of information you are not interested in.

VISUAL ID: A feature in which a visual (or graphic) indication is produced to help identify the target, its depth and possible size on a display. Also called VID, TID, VGI or VDI.

VGI: A Visual Graphic Image. See VISUAL ID.

VISUAL INDICATOR: A meter, digital or analog that signals a target's presence.

VLF (Very Low Frequency): A metal detector that normally operates in the 3-30 kHz frequency range. Also known as Induction Balance, it is probably the most popular detector technology in use today. In a VLF metal detector, there are two distinct coils: the Transmitter (outer) and Receiver (inner) coils. Also see FREQUENCY.

VLF/DISC: Term associated with detectors capable of mineral-free operation in both the Discriminate and All-Metal modes.

VLF/TR: A class of detector that can operate in both the All-Metal, Ground Balance mode and the No-Motion Discriminate, Non-Ground Balance mode.

WIDE RESPONSE: A target that produces an audio signal over an area wider than the searchcoil diameter, as opposed to Tight Response which produces a signal much smaller than the coil diameter.

WIDE SCAN: A coplanar searchcoil with two "D" shaped transmit and receive windings (coils) positioned back to back and overlapping. This coil type is capable of detecting a target across at least its full diameter. Also called DD, 2-D or Double-D.

ZERO DISCRIMINATION: Used to describe detectors whose discrimination control allows the acceptance of All-Metals at zero setting.