Bar Location Techniques - Elcometer protovale P330 Operating Instructions Manual

If you now bring the head up to a 25mm bar at 30mm distance, the display
might show
The signal-strength stripe at the bottom has grown (the bigger bar
produces more signal), and the indicated cover (based on a ø16 bar) has
therefore been under-estimated; but the cover estimated by AutoSizing (of
an unknown bar size) is correct, and the estimated bar size is
also approximately correct.
To return to the main Menu, press .

Bar location techniques

The search head is directional, that is, it has maximum sensitivity to bars
running parallel to the long axis of the head, and least sensitivity to those
at right angles.
Therefore, the head should be orientated parallel to the bars being sought,
and then scanned sideways across them.
When the reinforcement consists of two layers, the second layer running
transverse to the first, the scanning is done twice, once for each layer.
If the two layers are made up of bars of similar size, it is usually easier to
look for the nearer layer first (as it gives a stronger signal, and is least
influenced by the other bars); and then look for the second layer, this time
scanning the head in lanes between the now-known positions of the first
layer of bars. But if the nearer layer is made up of relatively thin tie-wires
or stirrups, and the deeper layer comprises much larger main structural
bars, it will often be easier to look for the second layer first.
Although the LOCATE mode shows a signal-strength stripe running across
the bottom of the display as a visual aid in finding the maximum signal, it
will be found that the built-in audio signal is much more informative (and
does not require you to look at the display); to switch this on, rotate the
AUDIO knob clockwise away from the (mute) position towards the
position.
The sound is at its most sensitive when the AUDIO knob is adjusted to
produce a slow tick-over when the head is held away from all metal.
However, especially when locating shallow or closely-spaced bars, the
resolution will be improved by turning the AUDIO knob back somewhat
from the optimum-sensitivity position; (but if you turn it back too far, you
may miss some deeper-than-average bars).
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