5. Measuring with Pundit Lab
The Pundit Lab can be used for several applications including the following:
Pulse velocity measurement
Surface velocity measurement
Estimating the dynamic elastic modulus of samples (with the shear wave transducers)
only. Estimating compressive strength using pulse velocity alone or in combi-
nation with a rebound hammer
Three transducer arrangements are commonly used.
Wherever possible use the direct arrangement as this ensures the maximum signal transmis-
sion between the transducers. The semi-direct arrangement is less sensitive than the direct,
but more sensitive than the indirect arrangement. The path length is the distance between the
The indirect method is particularly useful for determining crack depth, surface quality or in the
case when only one surface is accessible.
Basic preparations are common to each application. The distance (path length) between the
transducers should be measured as accurately as possible. It is very important to ensure ad-
equate acoustic coupling of the transducers to the surface under test. A thin layer of couplant
should be applied to the transducer and the test surface. In some cases it may be necessary
to prepare the surface by smoothing it.
For compound measurements and uniformity testing a test grid should be drawn out on the
Rebars affect the ultrasonic measurements as the signal will
travel faster through the rebar than
through the concrete. The location of rebars should be determined using a rebar locator such
as Proceq's Profoscope and ultrasonic tests should be positioned so as to avoid them. BS
1881 Part 203 gives information on the effect of rebars on the expected results.
The standard measuring procedure is:
Position the transducers.
Reposition the transducers (compound measurements only).
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