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7.
Sensitivity Control
3.
The Sensitivity control, located at the bottom of the control panel, allows
the level of sensitivity to be adjusted to suit the conditions in which you are detecting.
It is often thought of in terms of a depth control and it is, to a point, but more
importantly it also makes the unit more or less sensitive to interference caused by
ground "mineralisation", and electromagnetic fields.
At the most anti-clockwise position, this control "clicks" into the Auto position. In this setting the Sovereign GT
will automatically adjust the level of sensitivity to the most stable level under the prevailing conditions.
Beginners should operate the unit in Auto, until they become more competent in its operation.
Turning the control clockwise will "click" the Sovereign GT out of the Auto setting into manual sensitivity.
As this control continues to be turned in a clockwise direction the level of sensitivity will be reduced. At the most
clockwise position, the Sovereign GT is set at "minimum" sensitivity.
Experienced operators, when detecting in wet sand at the beach, should set the Sensitivity control out of Auto
and slowly turn the control clockwise until minimal false signalling is experienced. This will give the maximum
sensitivity while maintaining a smooth threshold. In general, the more moist the beach sand, the more clockwise
the knob must be turned.
When operating the Sovereign GT in heavily mineralised ground, the operator should again reduce the
sensitivity until the ground balance is able to cope with the mineralisation.
NOTE: Often a sensitivity setting that gives a smooth threshold is preferable to a high sensitivity that causes
undue noise or instability that makes it difficult to hear subtle target signals. Detecting with a smooth threshold
will often mean that you are able to hear targets to a greater depth than with a noisy threshold.
The incidence of false signalling is minimized if the operator concentrates on sweeping the coil as parallel to
the ground surface as possible. In summary, for greatest detection depth:
• Keep the coil sweep as parallel to the ground as possible.
• Turn the sensitivity knob as anti-clockwise as possible, (within the manual region) so that minimal false
signals occurs.
• This setting will need to be altered, depending on the mineralization or sand moisture level.
Advanced users operating inland, can operate the unit in either Auto or in Manual. In more mineralised soils,
a reduced Manual setting is recommended. Note that "hot rocks", "Roman Pennies" or some ancient
red/orange/brown pottery or tiles may cause the unit to respond as if the targets are ferrous. This is not a false
signal, but the correct response, and indicates that the unit is set at a relatively high sensitivity. It is also
highly recommended that a very slow sweep of the coil, across the ground, will reduce false signals.
If detecting non-ferrous items in a high trash area, a beginner may prefer to use Auto sensitivity and Disc – Iron
Mask / Off (see chapter 7.5.1) as this setting will provide a smoother operation, and keep "broken" or "chopped"
signals to a minimum.
Advanced users operating in non-mineralised soils or areas of high trash concentration should set the
sensitivity control out of Auto and into the variable Manual region. The control should be set as anti-clockwise
as possible (out of Auto and into the variable manual region), so that minimal false signalling occurs.
This setting will depend on the degree of soil mineralisation and metal junk concentration and may need to be
altered as the environment changes.
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7. control panel
7.
Threshold Control
4
.
Located at the bottom right of the control panel, the Threshold control allows for
adjustment of the background hum. This background "threshold" or "hum" aids in the
location of targets.
Small targets or large, deep targets may not produce a distinct target signal but rather
cause only a slight change in the threshold tone.
Ideally, this control should be set to a position where the threshold tone is just audible. At this level, the
presence of small or deep targets will be more easily recognised. Turning the Threshold control in a
clockwise direction will increase the threshold level. At the most clockwise setting, the threshold is at
its maximum.
A threshold level that is too high will mask out the small or deep targets, while a "silent" or non-audible
threshold may not allow the small change in threshold tone created by small or deep targets to be heard.
7.
Silent Search/Threshold
4.1
When in the discriminate mode, the Sovereign GT will vary the tone of an audio signal
depending on the conductivity of the target; ie. a highly conductive target will produce a high
pitched tone, while a less conductive item (such as foil) will produce a lower pitched tone.
The advantage of the Sovereign GT over other detectors is that the tone of the threshold will
also change. After the target signal is heard, the threshold "hum" will return in a pitch similar to the pitch of
the signal. When the target signal is nulled due to discrimination or notching, the threshold will again return
in the higher or lower pitch of the target conductivity.
For example, if you are searching in the Discriminate mode and you have just detected a coin, the threshold
will remain at the tone of the coin signal, but when you pass over a junk target such as a nail, the Audio will
NULL (go silent) over the nail, and the threshold, when it returns, will drop to a lower tone. This can be a
useful feature, as unlike other detectors using Silent Search discrimination modes, you still ignore the junk
targets, but you know when you have passed over them and can estimate the conductivity that they have.
( see 7.6 Discrimination & Notch descriptions)
The other advantage of the threshold-based Discriminate mode is that on occasions, the only thing that may
alert you to the presence of a very deep target is a change in threshold pitch. This is a common occurrence
in very junky sites, or if you are sweeping faster than normal.
However, for new users of BBS technology, this may initially be a little confusing so, to simplify things a
little, Minelab have added a Silent Search discriminate mode option to the Sovereign GT. In this mode,
targets will still produce different tones based on conductivity, but you will not hear the changes in threshold
tone, or the Nulling of discriminated objects. A slightly faster sweep speed is also possible, which makes the
Silent Search mode ideal in areas of low target concentrations, such as the beach, where ground coverage
is just as important as recovering the really deep targets. If a rich pocket or area is located, the operator can
select the Threshold mode and slow down their sweep to ensure all targets are recovered.
To operate in Silent Search mode, you need to start with the switch in Threshold position and, using the
Threshold control, lower the level until it is just audible as you would if you were searching with Threshold.
Once you have this level of threshold, flick the switch to Silent Search. The threshold will now disappear but
a faint target signal will still sound.
NOTE: If you were to have the threshold level set too low before going into Silent Search, you could find that
the very soft target signals may not be audible. If your threshold level is too loud before
switching into silent search, the threshold will become softer but still audible.
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