Measuring Depth Of Cover; How The Cm52 Covermaster Works; Basic Depth Measurement - Elcometer Protovale CoverMaster CM52 Operating Instructions Manual

4. MEASURING DEPTH OF COVER

4.1 How the CM52 CoverMaster works

The CM52 CoverMaster measures depth of cover from the strength of the eddy current
'echo' signal. The stronger the signal, the shallower the cover or the larger the bar
diameter.
To make an accurate measurement it is necessary to set the DIAM control to the
diameter of the bar.
Accurate depth measurement also requires that the search head is positioned parallel to
the bar and centred above it – which is why the location techniques described in section
3 need to be practised first.

4.2 Basic depth measurement

1. Set the MODE switch to CALibrate.
2. Set the DIAM switch to the known diameter of the bars in millimetres. Accuracy
in setting the diameter is much more important for depth measurement than it is
for location.
3. Switch on the instrument by turning the ZERO control clockwise. Check that the
LOW BATteries indication is not showing – if it is, recharge the batteries.
4. Hold the search head well away from any metallic object – including wristwatch,
rings, metal belt buckle, the main CM52 unit or the metal fittings on the neck
strap. Advance the ZERO control clockwise until the analogue meter needle is
exactly in the centre of its scale.
The display gives the most sensitive zero indication, but it does not need to be
set exactly to zero except when measuring cover depths approaching 80mm.
The following table shows the acceptable range of zero adjustment
5. Turn the MODE switch to DEPth+audio. A rapid ticking sound will be heard, and
the digital display will read a high value (such as '112
6. Place the black face of the search head directly over a bar of the correct
diameter, and carefully adjust its position for the highest-pitched sound.
7. The digital display is now reading the cover depth in millimetres. For example, a
reading of '038
the search head to obtain the minimum reading – this is the correct value. If the
search head is not accurately positioned, the depth display will read high.
Cover depth
(mm)
less than 50
60
70
80 and more
m
' represents a depth of 38mm. Make further fine adjustments to
Acceptable
'zero setting'
–015 to +015
–005 to +005
–002 to +002
exactly 000
m
').
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