51
M
EASURING
WELDED
MESH
AND
JOINED
BARS
R
17 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, 6 and 9 (pages 18 to 24 and 27
to 30). This section highlights the additional factors which must be considered when measuring
welded mesh or joined bars.
When 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.
When 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 27. 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.
Figure 28. Minimum strength signals at centre of single loop
331.book Page 51 Thursday, March 12, 2009 9:46 PM
