88 89Glossary
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 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 wire windings 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 Series have an
'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 which do not contain significant levels
of iron. Non-magnetic metals such as Gold,
Silver, Copper, Brass, Lead or Aluminium.
Pinpoint
The method for 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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