© 2014 Proceq SA
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2. Measuring Principle
2.1 Measuring Principle
The Profometer PM-6 uses electromagnetic pulse induction technology
to detect rebars. Coils in the probe are periodically charged by current
pulses and thus generate a magnetic field. On the surface of any electri-
cally conductive material which is in the magnetic field, eddy currents are
produced. They induce a magnetic field in the opposite direction. The
resulting change in voltage can be utilized for the measurement.
Coils
Concrete
Rebar
Magnetic Field
Figure 1:
Measurement principle
The Profometer PM-6 uses different coil arrangements to generate sev-
eral magnetic fields. Advanced signal processing allows locating a rebar
as well as measuring of cover and rebar diameter.
This method is unaffected by all non conductive materials such as con-
crete, wood, plastics, bricks etc. However any kind of conductive materi-
als within the magnetic field (sphere of approx. 200 mm / 8 inch radius)
will have an influence on the measurement.
NOTE! Remove all metallic objects such as rings and watch-
es before you start measuring.
2.2 Calibrated Measuring with Profometer PM-6
The Profometer PM-6 is calibrated to measure on a normal rebar ar-
rangement; which is an arrangement of non-stainless steel rebars fas-
tened with binding wires only e. g. when measuring on welded mesh
wires the cover and diameter readings must be corrected (see “3.7 Prac-
tical Hints”). The following information on accuracy, measuring ranges
and resolutions refer to measurements on normal rebar arrangements.
2.3 The Measuring Range
The measuring range is dependent on the bar size. The expected ac-
curacy of the cover measurement is indicated in the graphic below. It
complies with BS1881 part 204, for a single rebar with sufficient spacing.
[inch] [mm]
Rebar size
Cover depth
Spot probe
measuring range
Standard
measuring range
±3 mm
±2 mm
±1 mm
±1 mm
[mm]
[
1
/
16
inch]
153 mm
50 mm
Large
measuring range
measuring
accuray
185 mm
100 mm
Up to the indicated limits the cover is measured and displayed.
In the Locating Mode a rebar is shown. In the Single-Line Mode the cover curve is shown but a
rebar is only set up to 90 % of the maximum cover.
Figure 2:
Measuring ranges and accuracy
