THE MINELAB ‘GP extreme ’
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CONTROL FUNCTIONS
Boost (Shallow/N/Deep)
Figure 4.3
Enhances the signals produced by different types of targets.
•
Shallow enables target signals, from small objects close to
the surface of the ground to be amplified. This allows for
easier detection. This setting is best suited for 'quiet' ground.
•
N (Normal) may be used for normal detecting conditions.
This setting responds to all signals without boosting.
•
Deep may be used when searching for large targets at
greater depth in 'noisy' ground. Random soil signals are
smoothed, making small changes in the audio signal from
large deep targets easier to hear. This may mask some
signals from very small targets near the surface.
Threshold
Figure 4.4
Adjusts the background audio signal or 'threshold' level.
The Threshold control should be set just above the point where
the threshold is just audible and stable.
This level should not be at a level where prolonged use may be
irritating. Ideally it should be a smooth, gentle hum.
NOTE
Small targets or large deep targets may not produce a
distinct target signal, but may cause only a small variation in
the threshold level. If the threshold level is set too high or
too low, these very small variations may be missed.
In Figures 4.5 - 4.7, the dotted line represents the level at which
the audio output becomes audible; signals cannot be heard if
they are below the dotted line.
If the threshold level is set too high then small variations in audio
signal might not be discernible above the threshold level (Figure 4.5).
An example of this would be to hear a whisper within a crowded
noisy room.
Figure 4.5
Threshold control too low
P0509-A
Figure 4.6
Threshold control too high
P0509-B
Figure 4.3
Boost switch
Boost
P0519-A
Figure 4.4
Threshold control
Audio
P0520-A
THE MINELAB ‘GP extreme’
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CONTROL FUNCTIONS
If the threshold level is set too low there is no audible background
signal and small target signals will not go above the threshold of
audibility (Figure 4.6).
HINT
A soft audible headphone signal which is comfortable to
listen to for extended periods is recommended (Figure 4.7).
Volume
Figure 4.8
Sets a maximum limit on the loudness of the target signal
obtained from a large target. Refer to Figures 4.9 - 4.11. The
dotted line in these figures represents the level of volume set by
the volume control.
•
If the Volume is set to maximum (fully clockwise), the target
signal is unaltered and proportional to the target size and depth
(see Figure 4.9).
•
If the Volume control is turned down to half way, the target
signal is unaltered for a small target, but is limited for a
bigger target (see Figure 4.10).
•
If the Volume were to be turned down close to minimum, it
potentially will limit all signals to such a degree that most
targets will be lost (see figure 4.11).
NOTE
Threshold should be reset after adjusting the Volume level.
Figure 4.8
Volume control
Audio
P0521-A
Figure 4.9
Maximum volume
P0508-A
Figure 4.7
Threshold control just right
P0509-C
Figure 4.11 Minimum volume
P0508-B2
Louder
Mid-range
Figure 4.10 Mid-range volume
P0508-B
