Elcometer Protovale 331 Operating Instructions Manual page 37

1. Hold the search head in contact with the concrete surface. The centre of
the search head should be in the centre of the space between the bars as
shown in Figure 18.
2. Press the ZERO softkey to zero the Covermeter.
3. Move the search head to the measurement position and then carry out
orthogonal sizing as previously described in section 9.2 on page 29.
The aim of this technique is to subtract the 'background metal' signal; but it only
provides an estimate of that background. As a result, it tends to over-
compensate for the errors and therefore may result in an under-estimate of bar
size (and cover).
Nevertheless, comparison with results from orthogonal sizing conducted with a
standard zeroing technique can be used to get a slightly pessimistic estimate of
the probable error (or degree of confidence) in the result.
M
EASURING SIZE OF REINFORCEMENT BARS
Figure 18. Zeroing
R
( )
ORTHOGONAL
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