Elcometer Protovale 331 Operating Instructions Manual page 25

If the bars in the nearer layer are thin compared with those in the deeper
layer (Figure 10):
Search for the deeper layer first; it gives a stronger signal, and is least
influenced by the other bars. Then search for the nearer layer, this time
scanning the head in lanes between the now-known positions of the deeper
layer of bars.
• The first scan locates the second (bottom) layer.
• The second scan locates the nearer (top) layer.
Second scan
Figure 10. Scanning layers of bars of different size
(This situation is typical of a nearer layer consisting of relatively thin tie-wires or
stirrups, and the deeper layer consisting of much larger main structural bars.)
L
OCATING REINFORCEMENT BARS
First scan
R
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