Glossary Of Terms - Minelab GPX-4000 Quick Start Manual

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Glossary of Terms

Control Box
This encloses the electronic circuitry
of the detector. The control box
generates the Tx (transmit) signals
sent by the coil and processes the Rx
(receive) signals detected by the coil.
All user selectable functions are located
on the front and rear panels of the
control box.
Discrimination
The ability of a detector to determine
if a located target is made from ferrous
metal (iron or steel) or non-ferrous
metal (non-magnetic).
Double-D Coils
Two windings of wire that overlap in
the shape of two D's (one reversed).
The characteristics of a Double-D
coil are stability, especially in heavily
mineralised ground, good depth and
sensitivity and a very thorough search
pattern.
Electromagnetic Field
Commonly called the 'signal from
the coil'. An electromagnetic field is
generated within the wire windings of
the search coil and this field is pulsed
or sent into the ground. The presence
of a metal target in the ground will
disturb the pattern of this field and this
disturbance is sensed by the receive
system of the detector and indicated to
the operator by an audible 'beep'.
False Signals
These sound similar to target signals
but are caused by other factors.
Common causes for false signals are
incorrect Ground Balance, hot rocks,
signals caused by knocking the coil
on obstacles, etc. With experience,
the operator will learn methods to
minimise false signals and to hear
subtle differences between target
signals and false signals.
Ferrous Metals
Metals composed of or containing
iron. A ferrous item will be attracted
to a magnet and is predominantly or
completely made of iron or steel.
Ground Balance
The ability of the metal detector to
compensate for the effects of ground
mineralisation. The GPX-4000 has
'automatic Ground Balance'. When
Ground Balance is used in the Tracking
setting it continually compensates for
changes in the ground mineralisation.
Halo Effect
After a metal object has remained
undisturbed in the soil for a
considerable amount of time, a
diffusion occurs around the object.
This has the effect of the object
appearing to the detector to be
a larger size.
Hot Rock
An individual rock which has a high
degree of mineralisation in comparison
to the surrounding ground around it.
Due to this difference, the detector
does not have the opportunity to
Ground Balance to the individual hot
rock so therefore gives a false signal.
The signal will diminish rapidly by
increasing the coil height above the hot
rock.
Interference
Electricity or radio waves in the area
being detected can cause instability
or chattering of the Threshold.
Interference commonly occurs due to
power lines, underground cables, radar,
other detectors or climatic conditions
like thunderstorms.
Mineralisation
Most ground contains some minerals,
which can cause false ground signals
to be detected. Heavily mineralised
ground requires different detector
processing than does neutral or lightly
mineralised ground. Ground containing
heavy salt concentrations require
entirely different processing again.
Monoloop Coils
Monoloop coils are the style of coil
where the multiple strands of wire are
wound in a single loop around the
circumference of the coil. The field of
search of Monoloop coils tends to be
cone shaped. They provide greater
depth and sensitivity compared to a
Double-D coil of equivalent size in low-
medium mineralisation.
Non-Ferrous Metals
Metals that do not contain significant
levels of iron. Non-magnetic metals
such as Gold, Silver, Copper, Brass, Lead
or Aluminium.
Pinpoint
The method of determining the precise
location of a target prior to digging.
Pinpointing uses the design of the
search coil windings to determine the
exact position of the detected target.
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 detect a metal
item in the ground.
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