Velleman CS990XD User Manual - page 5
CS990XD
VELLEMAN
5
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On/Off Switch and Tune Control
This control is a combined on/off switch and rotary tune control. Fully anticlockwise to the clicked position is power off.
To turn the detector on, rotate the control clockwise from its indented off position. To tune the detector, adjust the control to
give the preferred level of audio (from the internal loudspeaker or headphones). For best performance, the audio should be
adjusted to threshold, when the sound is just beginning to break through, since this is when the ear is most sensitive to small
changes, and it is important to maintain this threshold when searching to achieve the maximum depth.
The meter gives a visual indication of the audio level (unless battery check or meter disc is selected) and will read midscale
when tuned at threshold.
The tune control is used in conjunction with the retune button which should be depressed when making adjustments to the
controls.
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Retune Push Button
Should the audio level change during searching other than resulting from a target, such as from drift occurring from warming
up, press (and release) the retune button to recover the threshold sound as set on the tune control. The retune button should
also be held down when making adjustments to any of the detector’s controls.
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Ground Exclusion Switch and Disc Mode Switch
Firstly, what is ground exclusion?
On some sites mineralisation caused by iron oxides makes it difficult to operate a detector successfully. The effect of these
minerals is termed ground effect. In practice, if the detector is not correctly adjusted, the signal alters if the search head is not
swept at a constant height above the ground. However, by operating the detector at the correct exclude point this ground
signal can be eliminated. The elimination of this signal is known as ground effect exclusion or simply ground exclusion. When
operated at the inland ground exclude point, all metals give a positive response so this is sometimes called all-metal mode.
What is discrimination (disc)?
Like mineralised ground, metals and wet salt sand too, have a characteristic exclude point. By operating the detector at the
beach exclude point, iron and small ferrous items produce a negative response, but valuable targets still produce a positive
signal. By operating at a higher exclude point, still small pieces of silver (aluminium) paper will also produce a negative
(reject) signal.
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Level Control
The discrimination level of the beach/disc detector in the CS990XD is centred at about that of wet salt sand but can be varied
from iron reject through aluminium foil reject by adjusting the level control. (The level control also adjusts the exclude point of
the meter disc and meter + audio disc.)
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Inland and Disc Mode Switch
With inland selected the CS990XD operates at a fixed level of ground discrimination. This inland ground exclude point is
factory set on the CS990XD. All metal targets will produce an increase in audio volume in this mode regardless of the level
control setting. The beach/disc detector remains operating and can be selected to drive the meter or control the audio pitch
by selection on the disc mode switch. The level of discrimination of the beach/disc detector can be adjusted by the level
control.
The inland mode is used on mineralised inland sites and can be used in conjunction with any one of the disc modes
described below.
By selecting the meter disc mode the meter needle moves to the right for good targets and to the left for reject targets.
By selecting the meter + audio disc mode the meter moves to the right for good targets and to the left for reject targets and
the audio pitch increases for good targets and decreases for reject targets.