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Glossery Of Metal Detecting...more
to come later |
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A
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| Air
Test: |
A
test performed by passing metal samples of various sizes under
the detector's search coil to check target responses. This test
is not an accurate indicator of ground depth penetration. |
| Alkaline: |
A
type of battery characterised by the ability to sustain longer
periods of current drain and greater storage life than standard
carbon-zinc batteries. |
| All
Metal: |
Describes
any mode or control setting that allows total acceptance of
metal targets. Usually associated with ground balance mode. |
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Audio ID: |
Circuitry
producing different audio tone for each target's conductivity
range, eg low tone for iron, high tone for coins. |
| Auto
Tune: |
Circuitry
which continuously retunes the detector's threshold to the initially
tuned audio level at a preset rate after drift and/or target
rejection. |
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B
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| Back
Reading: |
A
false signal caused by a rejected target coming within one inch
of, or contacting, the bottom of the search coil when operating
in the discriminate mode. |
| Bench
Test: |
An
air test to determine at what approximate discriminate settings
various metal samples are rejected or accepted. The test is
conducted in non-metallic area. |
| Black
Sand: |
One
of the most extreme components of non-conductive, negative ground
minerals. Also called magnetite and magnetic iron oxide. |
| Body
Mount: |
A
method of fastening the detector's control box to expand usability
for shallow water hunting. Also known as hip mount. |
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C
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| Carbon-Zinc: |
Standard
dry cell batteries. |
| Coin
Depth Indicator: |
A
visual indicator, used in conjunction with calibrated circuitry,
to show depths, in inches or centimetres, of buried coins. |
| Concentric: |
A
search coil configuration using one or more transmit, and one
receive, winding having unequal diameters aligned on a common
center, most recently arranged on the same plane and called
'coplaner concentric'. |
| Conductive
Salts: |
Wet
salt sand which produces a positive rise, or metallic response
on an air tuned threshold. |
| Conductivity: |
The
measure of a metal target's ability to allow eddy currents to
generate on its surface. |
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D
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| Detection
Pattern: |
The
densest or strongest region of the search coils electromagnetic
field where detection occurs. It is balloon shaped and changes
in size directly in proportion to target surface area. |
| Detuning: |
Adjusting
the audio threshold into the null or less sensitive tuning zone.
It is also a method of narrowing a target's signal width manually
for precise pinpointing. This is accomplished by returning to
audio threshold over the target response area. |
| Discrimination:
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Adjustable
circuitry which ignores or nulls audio responses from a specific
conductivity range allowing positive responses to be heard from
metals higher in conductivity above the discriminate control
setting. Designed primarily to eliminate audio response from
unwanted metals. |
| Drift:
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A
loss of threshold tuning stability caused by temperature change,
battery condition, mineral content, and/or detector design. |
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E
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| Eddy
Currents: |
Small
circulating currents produced on the surface of metal by the
transmitted electromagnetic field. These currents then produce
a secondary electromagnetic field which is then detected by
the search coil receiver windings, resulting in inductive imbalance
between the windings. |
| Electromagnetic
Field: |
An
invisible force extending from top to bottom of the search coil
and created by the flow of alternating oscillator frequency
current around the transmit winding. |
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F
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| Faraday
Shield: |
A
metal foil wrapping of the search coil windings for the purpose
of eliminating electrostatic interference caused by wet vegetation. |
| Ferrous: |
Descriptive
of any iron bearing material. |
| Ferrous
Oxide: |
An
oxidised particle of iron which becomes non-conductive and makes
up the natural negative ground mineral matrix. Hematite, which
is also an iron oxide, will respond as positive or metallic. |
| Frequency: |
The
number of complete alternating current cycles per second produced
by the transmit oscillator. Measured in Hertz (Hz). VLF = Very
Low Frequency; LF = Low Frequency; MF = Medium Frequency; HF
= High Frequency. |
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G
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| Ground
Balance: |
A
state of operation in which specialised circuitry can be adjusted
to ignore the masking effect that iron ground minerals have
over metal targets. |
| Ground
Balance (Operator Adjust): |
A
feature requiring a manual control adjustment procedure to neutralise
the effects of negative minerals in the search matrix. |
| Ground
Balance (Factory Preset): |
A
feature which eliminates the manual ground balance control and
its adjustment from the operators set up procedure. This adjustment
is performed internally by the factory to optimise operation
over an average range of non-conductive soils. |
| Ground
Filter: |
Complex
circuitry found in motion type detectors which separates mineral
signals from metal signals, allowing the metal signal to be
further processed by the discrimination circuitry. |
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H
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| Hot
Rock: |
A
rock which contains a higher concentration of non-conductive
ground minerals than the surrounding matrix to which the detector
is balanced. A metallic (positive) 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 balance mode over
these rocks. |
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I
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J
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K
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L
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| LCD
(Liquid Crystal Display): |
Used
on a metal detector as a graphic visual indicator. |
| LED
(Light Emitting Diode): |
A
semiconductor which produces an illuminated visual response. |
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M
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| 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. |
| Metal: |
Metallic
substances: iron, foil, nickel, aluminium, gold, brass, bronze,
lead, copper, silver, etc. |
| Metal
Detectorist: |
A
person operating a metal detector in the field. This name is
preferred by many to 'treasure hunter'. |
| Mineral
Free Discriminator: |
Detector
that can reject or ignore trash metals while simultaneously
eliminating or balancing ground mineralisation. |
| Mineralised
Ground: |
Any
soil that contains conductive or non conductive components. |
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N
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| Negative
Ground: |
Soil
that contains non-conductive minerals which have a negative
or nulling effect on air-tuned threshold. |
| Neutral
Ground: |
Soil
lacking non-conductive or conductive mineral properties. It
lacks mineralisation. |
| NiCad
(Nickel Cadmium): |
A
rechargeable battery. |
| Non-ferrous: |
Not
of iron; metals including gold, silver, copper, lead, tin, brass,
bronze, etc. |
| Non-Motion: |
Mode
of operation that does not require search coil movement to trigger
target response. |
| Notch
Accept: |
Operation
whereby all target responses are 'tuned out' except those the
instrument is adjusted to accept in the notch window. |
| Notch
Discrimination: |
Circuitry
which allows a desirable window of targets to be accepted within
the rejection range of unaccepted targets. |
| Notch
Level: |
A
control used to select the target level of conductivity which
the notch filter will act upon. |
| Notch
Reject: |
Operation
whereby all targets within the notch width (at the chosen notch
level) will be 'tuned out'. |
| Null: |
Zone
just below audible threshold in detector tuning. The term also
refers to the momentary drop, or quiet response, of threshold
audio as the search coil passes over a discriminated or rejected
target. |
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O
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| Overlap: |
The
amount of search coil swing advance not greater than the search
coil's physical diameter. |
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P
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| Pinpointing: |
Finding
the exact target location with respect to a search coil's designated
centre. Accomplished by interpreting the centres of audio response
width in perpendicular directions or scans. |
| PI
(Pulse Induction): |
A
metal detector with a transmitter circuit that pulses an electric
current into the ground before quickly shutting down. The eddy
currents dissipate immediately from wet salt sand and other
ground minerals because they are poor conductors. Because they
are better conductors, metals hold the eddy currents, and when
the receiver circuit comes on, it picks up the returning signals
from metal objects. |
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Q
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R
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| RF-Two
Box: |
Radio
frequency detector with 2 separate coils, the detector is capable
of detecting large, deep objects while naturally ignoring small
targets such as nails and individual coins. |
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S
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| Scan: |
The
effective search coil detection width. Also refers to search
coil movement over the ground. |
| Scrubbing: |
Search
technique in which the search coil is pressed and held in contact
with the ground in order to maintain an even audio threshold.
With newer detectors, this technique is used to gain depth. |
| Search
Coil: |
A
circular (or other shaped) plastic housing containing single
or multiple transmit and receive wingdings in a specific orientation
or configuration to emit and receive signals from ground and
targets. (Also called a 'loop' or a 'coil'.) |
| Search
Coil Cable: |
An
electrostatically shielded cable of conductors (wires) which
convey signals to/from the search coil and control housing. |
| Sensitivity: |
The
measure of capacity of a 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. |
| Silent
Search: |
(=
silent operation) A detector capable of producing a target signal
while operating below the threshold audio. |
| Skid
Plate: |
(=coil
cover or scuff cover) A protective cover for the search coil
bottom. |
| Slow
Motion: |
A
description of search coil speed required to operate the motion
discriminate mode. |
| Sweep: |
The
motion employed in moving the search coil across the ground. |
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T
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| Target
Masking: |
Occurs
when large pieces, or high concentrations, of trash metals drive
the threshold into the null zone, suppressing weaker responses
from deeper or smaller targets. |
| Ten-Turn: |
A
control which can be manually rotated ten times to cover the
full electrical range of the function. Usually associated with
tuning or ground balance function. |
| TH'er: |
Treasure
Hunter |
| TH'ing: |
Treasure
Hunting |
| Threshold: |
An
audible reference point for tuning the detector in order to
ground balance it. The threshold tone also establishes the minimum
sound level for deep targets in the discriminate mode. |
| TR
(Transmit/Receive): |
The
term used to describe an early type of detector, still produced
by some manufacturers. Electromagnetic field distortion caused
by mineralised ground interferes with depth penetration because
this type of detector does not ground compensate. It does however
balance salt water effects. Therefore, it is primarily used
for searching in salt water and on low mineral salt water beaches. |
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U
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V
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| Visual
ID: |
Visual
indication used to identify targets. |
| VLF/DISC: |
Term
associated with detectors capable of mineral free operation
in both the discriminate and all metal mode. |
| VLF/TR: |
A
class of detector that can operate in the all metal, ground
balance mode, and in the non-motion, discriminate, non-ground
balanced mode. |
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W
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| Wide
Scan (2D): |
A
search head where the transmit and receive coil are arranged
in the form of 2 D's back to back. This type of coil offers
different characteristics to the concentric. It will cover a
larger area than a concentric coil of equivalent size and is
less affected by mineralisation. |
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X
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Y
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Z
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