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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 Rocks
A hot rock is an individual rock which has a particularly high degree
of mineralisation as compared to the average ground around it. Due
to this high difference, the detector does not have the opportunity to
ground balance on the individual rock so therefore gives a false signal.
Interference
Electricity or radio waves in the area being detected can cause
instability or chattering of the detectors threshold.
The types of interference commonly occur due to power lines,
underground cables, radar, other detectors or climatic conditions like
thunderstorms.
Mineralised Ground
Most ground contains certain minerals which can cause false signals
to be given by a detector. Heavily mineralised ground requires
different ground processing than does neutral or lightly mineralised
ground (see Ground Balance).
Ground containing heavy salt concentrations require entirely
different processing again (see salt).
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 tend to be cone shaped.
Non - Ferrous Metals
Metals not containing significant levels of iron. Non-ferrous metals
are non-magnetic such as Gold, Silver, Copper, Brass, Lead or
Aluminium.
Pinpoint
The method of locating 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
RX 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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S a l t
The presence of high salt content in the ground being searched will
have a similar but different effect on the metal detector ground
balance as does mineralisation.
Salt content causes a negative (-) response rather than the positive (+)
response of laterite soils. The detector needs to therefore use
different filtering techniques to overcome this effect.
Search Coil
The search coil is the circular plate which is swept across the ground
surface during detecting. It transmits electromagnetic signals into the
ground and receives the response.
Search Pattern
The search pattern is the area of ground underneath the coil which
is being scanned. Depending on the style of coil (Double D or
Monoloop) and the RX mode being operated in (Normal / Enhance
/ Cancel) different coils will have a different shaped area being
covered by each sweep.
Threshold
The continuous audible level of sound emitted by the detector is
referred to as the Threshold. This threshold hum is the background
sound made as the detector operates. Threshold can be set
anywhere between silent and loud, but a soft, audible level is
normally suggested.
Target Response
The electro-magnetic effect generated by the metal target under the
influence of the TX field.
Target Signal
The audio signal (or change in threshold) caused by the presence of
a metal target as the coil passes across it.
Tracking
The function of Automatic Ground Balance where the ‘GP extreme’
makes continuous adjustments to the ground balance to compensate
for changes in the mineralisation of the ground.
TX
TX refers to the transmit signals or electromagnetic pulses, sent into
the ground by the coil.
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