AQ1B Compact Underwater Metal Detector
User Manual
3. Dive to the area of seabed to be searched.
4. Switch the unit on (one click, to the MIN position) and rotate the SET AUDIO
control to achieve the audio threshold point, keeping the search loop at arms
length and up from the seabed, this avoids detecting any metallic part of the
personal diving equipment or any buried items while the audio threshold is set.
5.
Begin your search by scanning the loop from side to side close to the seabed in a
fanning action. Avoiding passing the loop close to regulator, air tanks or
weightbelt as these or any other metal object on the diver, will give responses.
6.
If too much signal is obtained from the seawater such that the ‘SET AUDIO’
control will not achieve the desired threshold, turn the ‘REJECT’ control one
click at a time, clockwise until the ‘SET AUDIO’ control comes back into range.
NOTE 1: There are only 5 REJECT positions – from the OFF position you
can only turn the REJECT switch 5 clicks clockwise. Do NOT attempt to turn
the switch past the 5
th
position or permanent damage will occur.
NOTE 2: Different water depths will make a small difference to the threshold
Setting; this can be readjusted by the control knob. This depth related effect
does notoccur in fresh water.
Detection & Interpretation:-
Detection of buried metal is indicated by an increase in the audible signal when the
detector head is passed over a localised area of the seabed, with maximum response
being obtained when the head is centred over the object. The shallower the object the
more pronounced the peak response will be, whereas deeper objects tend to give a
more gradual change in response as the head is panned across the seabed.
NOTE
. Due to the sampling method of the AQ1B system it is possible when
detecting large metallic objects to go beyond the peak audible change and into a
“saturation” mode where the audible signal will disappear. The changes that occur in
the observed response are very non linear with proximity and in fact increase by a
factor of 64 times each time the distance between the object and the sense head is
halved, this ultimately leads to dramatic overload in the sampling system. In such
cases it is advisable to keep the sensing head sufficiently high above the seabed to
maintain an audible response whilst the sensing loop is passed over the area; this
should allow the centre of detection to be noted.
Rather than looking for the peak response over the centre of the metallic object
another option is to define the boundary of detection, this simply is done by noting the
point that detection is first indicated when scanning towards the object from multiple
directions. When excavating very small detected objects it can be sometimes difficult
to actually see the item, a method of checking sediment as it is removed is to put the
detector head to one side of the area to be excavated and drop the removed material
on to the sense head – this will easily determine if the object has in fact been removed
with the seabed material. The sense head can then be used to recheck the excavation
for any further metallic items.
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