© 2014 Proceq SA
24
3.7 Practical Hints
Effect of Setting Incorrect Bar Diameter
The accuracy of the cover measurement is also dependent on setting
the correct bar diameter.
The following chart gives an estimation of the error of the cover reading
for different rebar sizes if a default size of 16mm / #5 is set.
NOTE! The correct diameter can be set any time prior to
and after storage of data, see “3.5 Measurement Modes and
Storage of Data”.
[inch] [mm]
Ø 8 mm
Ø 16 mm
Ø 12 mm
Ø 20 mm
Ø 26 mm
Ø 34 mm
Ø 40 mm
[inch]
Standard range
Large range
# 2
# 3
# 4
# 5
# 6
# 8
# 12
Real Cover
[mm]
Err
or of Cover values
# 11
Spot probe
range
Ø 6 mm
Figure 25:
Error of cover measurement with diameter 16mm / #5 set.
Factors Affecting the Diameter Measurement
Two factors affect the determination of the rebar diameter. One is the
cover depth. The second is the spacing between neighboring bars. For
accurate determination of the diameter, the spacing between the rebars
must be greater than the limits shown in the drawing below with refer-
ence to the MC
14
/
15
.
NOTE! Diameter can be determined for rebars with cover not
exceeding 80 % of the standard range (63 mm, 2.50 inch).
S
2
S
1
S
1
>75 mm
>1.5 ”
S
1
: 130 mm / 5.20 inch without Neighboring rebar correction
50 mm / 2.00 inch with Neighboring rebar correction
(see “3.3 Settings”)
MC
14/15
min. 150 mm / 6 inch
Figure 26:
Minimum rebar spacings for correct readings
Rebar Orientation
The strongest signal results when the Center Line (CL) of the probe is par-
allel to a bar. The CL
16
of the Profometer PM-6 probe is the longitudinal
axis of the probe. This property is used to help determine the orientation of
the rebars (see Locating Mode in “3.5 Measurement Modes and Storage
of Data”).
Welded Meshes
The instrument cannot detect whether the rebars are welded to one an-
other or connected with binding wires. The two reinforcement types with
the same dimensions however create different signals.
The setting of the bar diameter must be slightly higher than the actual
