John Harun Mwau Facebook: Pro Metal Detecting
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.
H
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 – 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
I
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.
K
KEEPER – A slang word for a good metal detecting find.
kHZ (Kilohertz) – One thousand cycles per second, (see FREQUENCY).
L
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.
M
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.
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.
N
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.
O
ONE TOUCH – see TURN-ON-AND-GO
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.
P
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 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.
Q
QUICK RESPONSE – The measure of time it takes between metal sensing and full audio/visual response. Generally associated with all frequencies of TR detectors.
R
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 – The duration of time it takes a metal detector to respond to the next target after responding to the previous. Detectors with slow recovery speeds often are unable to respond to all targets in close proximity when discrimination is used.
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.
S
“S” HANDLE – A metal detector control shaft designed with offsets which increase operator comfort by reducing arm and wrist fatigue.
SCAN – To complete a detection path of search coil travel or sweep.
SEARCH COIL – The search head or housing which holds both transmitter and receiver windings (loops) aligned in a specific configuration, (see COAXIAL; CO-PLANAR; CONCENTRIC; DOUBLE D) Also known as a search loop or coil.
SEARCH COIL CABLE – A cable of electrostatically shielded wires which carries circuit board oscillator current frequency to the search coil and phase related target information back to the control housing.
SENSITIVITY – The measure of a metal detector’s capacity to sense changes in conductivity throughout the pattern of detection set forth by the search coil configuration, (see AIR TEST).
SIGNAL – A visual and/or audio response which alerts the operator to the presence of a metal object (see FALSE SIGNAL).
SIGNAL WIDTH – The ground distance measure of search coil travel in which target audio is sustained. Signal width is directly proportional to target size and ferrous content when operating in a non-motion all-metal mode.
SILENT OPERATION – A search mode which does not use constant threshold audio tuning to maintain sensitivity. Also called SILENT SEARCH.
SINGLE-FREQUENCY (see also FREQUENCY) – This is when a metal detector is designed to operate on one frequency of alternating current which is generated by the transmit oscillator and passed through the transmitter coil. Most detectors on the market operate on a single frequency, ranging from 1 to 70 kilohertz (kHz). Although this technology has served the industry well for years, the scientists found that a frequency that worked well in one area would often offer only marginal performance when used in another location. Ground mineralization, trash content, and target size all have an effect on how effective a detector transmitting a single frequency would operate.
SKID PLATE (Coil Cover) – A non-metallic cover placed on the search coil bottom for protection against abrasion.
SLOW MOTION – The rate or class of search coil sweep speed necessary to efficiently operate the motion discriminate mode.
SLOW RESPONSE – The measure of time associated with metal sensing and peak audio/ visual response. Generally associated with PI type detectors.
STABILITY – The quality of a metal detector circuit to resist external sources of thermal and electrical interference, (see DRIFT).
SURFACE BLANKING – A feature designed to eliminate the response from non discriminated targets lying within a predetermined depth. Based on signal intensities usually associated with shallow depths.
SWEEP – The width and/or speed rate of search coil scan.
T
TARGET – Any buried or hidden object to which a metal detector responds.
TARGET MASKING – The overriding or interfering effects large or numerous rejected targets have over desirable targets in close proximity.
TARGET SEPARATION – The ability of a metal detector to respond to individual targets within a closely spaced group.
TEN-TURN – Any control requiring ten revolutions of the indicator knob to cover the adjustment range of its function, (i.e. ground balance).
TEST GARDEN – A plot of targets intentionally buried by the detectorist. Arranged by size, depth, and composition for learning characteristic responses and comparing metal detector performances in a controlled environment.
THRESHOLD – The minimum audio level of tuning adjusted for optimum sensitivity. If your metal detector is not operated in Silent Search mode, the Threshold is heard as constant background “humming” during detecting. Threshold should be adjusted to a minimum audible level, so you can hear very small and deep targets. When a rejected target is detected, the Threshold sounds “blanks” or “null” (becomes silent) indicating that an undesired target is underneath the search coil. Threshold can be set anywhere between “no sound” (silent) and loud.
TH’er – An abbreviation for Treasure Hunter, an enthusiast in a hobby of metal detecting and treasure hunting. Also called a Metaldetectorist or Detectorist.
TOE – The northern section of search coil above the control shaft attachment point as viewed from above by the operator.
TONE CONTROL – An adjustment used to regulate the audio frequency or sound pitch to operator preference. Also used to contrast target response with external ambience.
TONE ID – Audio identification of a target based on a principle of relationship between the target’s conductivity and the tone’s pitch: the higher the conductivity, the higher the tone, i.e. the lowest pitch tone for iron, the highest pitch tone for silver.
TRANSMIT WINDING – The coil of wire which generates and transmits the primary electromagnetic field from within the search coil housing into the soil matrix.
TR (Transmitter/Receiver) – A class of metal detectors operating in a broad range of radio frequencies (i.e. VLF/TR; VF/TR) utilizing the inductive balance principle of metal detection. TR detectors are able to tell the difference between a ferrous and nonferrous object, but do not have enough depth in highly mineralized ground. TR detectors are obsolete now.
TURN-ON-AND-GO – A type of metal detectors that automatically eliminate the ground mineralization while in operation. This is achieved by the Automatic Ground Balance feature also called Automatic Ground Compensation, Auto Tune, etc., depending on a metal detector. Using a metal detector of this type, an operator does not have to manually adjust the detector’s ground balance before or during the detecting process.
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