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To activate UnderCover:
hold the head away from metal and start the
autoZero procedure by pressing the
button, and immediately, whilst it is
zeroing, press and hold the
button
(as a memory-jogger: the MINUS sign to set a LESS-than condition).
When the display shows
, release the button to get the full set-
up screen
Use the
and
buttons to decrease or increase the threshold value
respectively; press and release to change by 1mm, or press and hold for
larger changes. The set
button toggles the status between
and
.
When it has been set up as desired, press
to return to your LOCATE/
DEPTH mode.
Note that a bar of larger size than expected (rather than a bar at shallower
cover) may trigger the UnderCover alarm; however, having drawn your
attention, you will be able to see from the DEPTH or LOCATE display just
what is under the head.
Please note that, although an UnderCover facility appears to be a brilliant
idea and just what you've always wanted, it has some limitations which should
not be ignored: probably the most important, is that it will not distinguish
between
(a) a bar which is correctly present at more than minimum cover and
(b) a bar which is completely missing!
Similarly, a bar (or tie-wire) at just less than minimum cover, but of smaller
diameter than that set, may also fail to signal.
To disable UnderCover, enter its set-up screen as described above, and
toggle it to
(if you re-activate it later, it will have remembered the
previous threshold setting).
By default, UnderCover is OFF when you first switch the instrument on. This
can be reversed (active by default), by holding down the
button when you
switch on (with
); but you will still have to set up the minimum threshold
cover as before (unless the default value of 35mm happens to be
appropriate).
It is worth noting that this is not the only way of rapidly recognising bars with
less than the usual amount of cover. The section "Audible guide to cover"
describes how the ordinary sound signal will give a noticeably more intense
sound whenever the head passes over a bar which is shallower than its
neighbours, which is a much simpler way of drawing the operator's attention
to rogue bars without the need to set up the UnderCover mode.
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