Wall thickness measurement using the DMS Go+ 1 Introduction
DMS Go+ Edition 4 (05/2014) 1-17
Single-element mode (measurement
modes S-IP, S-PEAK, S-FLANK)
A single-element probe is used for transmitting and re-
ceiving the echoes in the single-element mode. For the
wall thickness measurement, the DMS Go+ determines
the time of flight between the entry echo and the first
echo exceeding the gate A. The entry echo (interface
echo) is generated at the transition of the initial pulse
from the probe to the test object.
Multi-echo mode
(measurement mode DUAL-MULTI)
The multi-echo mode is recommended, for example, for
the wall thickness measurement of coated test objects.
In this mode, two (or several) backwall echoes are used
for determining the wall thickness. The multi-echo mode
is possible using dual-element probes.
As before, an initial pulse is transmitted by a transducer
element to the test material. In the multi-echo mode,
however, part of the sound pulse energy is reflected
from the boundary surface between the coating (paint
coating) and the test material.
The rest of the energy of the first pulse transmitted pass-
es further through the test material and returns as a
backwall echo.
The time of flight between the two successive backwall
echoes is used, together with the material's sound ve
-
locity, for determining the material thickness. The
echoes from the coating are ignored in this process.
The operating principle of the multi-echo mode is shown
in the following figure.
probe
2nd backwall echo
boundary surface
between
coating and
1st backwall echo
coating
test object
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