Measuringwelded Meshand Joined Bars - Elcometer 331 Operating Instructions Manual

5
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MEASURING
V\iELDED MESH
AND JOINED BARS
1O
MEASURING WELDED MESH
AND JOINED BARS
The
procedures for
locating
and measuring depth
of cover of
welded mesh and
joined
bars are
similar
to those for reinforcement bars
as described
in
sections
5
and
6
(pages
14
to
19). This
section highlights the additional factors which must be considered when measuring welded mesh
orjoined bars
Vvhen searching
for
isolated reinforcing bars,
the
Covermeter induces eddy currents
within
the
individual
bars. Welded
mesh
reinforcements however create current loops
which produce
additional strong signals.
\Mren searching for
welded mesh reinforcements, it is
common to encounter three levels of signal:
Very
strong signals
Very
strong signals are obtained when the search head
is across
the centre bar
of a
double
or
'figure-of-eight'
loop.
These locations must not be used for
cover measurements.
Figure
15.
Strong signals at centre of 'figure-of-eight'
Minimum
strength signals
Minimum signals are obtained when the search head is
over the centre
of
a single loop
24
Figure
16.
Minimum strength signals
at
centre
of
single loop