Elcometer CG30 Operating Instructions Manual page 24

contact with a hot surface, it will begin to heat up, and through thermal expansion and other effects,
may adversely affect the accuracy of measurements.
17.3 MEASURING LAMINATED MATERIALS
The density (and therefore sound-velocity) of laminated materials may vary considerably from one
piece to another. Some laminated materials may even exhibit noticeable changes in sound-velocity
across a single surface. The only way to reliably measure such materials is by performing a
calibration procedure on a sample piece of known thickness. Ideally, this sample material should
be a part of the same piece being measured, or at least from the same lamination batch. By
calibrating to each test piece individually, the effects of variation of sound-velocity will be minimised.
An additional consideration when measuring laminates, is that any air gaps or pockets within the
laminate will reflect the ultrasound beam. This will be noticed as a sudden decrease in thickness in
an otherwise regular surface. While this may impede accurate measurement of total material
thickness, it does provide positive indication of air gaps in the laminate.
17.4 MEASURING THROUGH PAINT AND COATINGS
When measuring through paints and coatings the sound-velocity of the paint/coating may be
significantly different from the sound-velocity of the actual material being measured. An example of
this would be a mild steel pipe with approximately 0.6 mm (.025") of coating on the surface. The
sound-velocity of the pipe is 5918 m/s (.2330 in/µsec), and the sound-velocity of the paint is
2286 m/s (.0900 in/µsec). If the gauge is calibrated for mild steel pipe and measures through both
materials, the actual coating thickness will appear to be 2.5 times thicker than it actually is, as a
result of the differences in sound-velocity.
The error can be eliminated by using the echo-echo mode to perform measurements for
applications such as these. In echo-echo mode, the paint/coating thickness will be eliminated
entirely and the steel will be the only material measured.
17.5 DATA TRANSFER SOFTWARE
Software is available which allows data to be transferred from Models CG50/CG50DL to a PC.
Presently Elcometer NDT supplies NDT Link.
The Model CG50 gauge is supplied without any software but NDT Link is available as a free
download from the Elcometer NDT website www.elcometerndt.com.
The Model CG50DL gauge is supplied with a CD containing NDT Link.
To set-up other types of communications software
Model CG50
1. Start the communications software.
2. Configure the software using the following
parameters:
Data Bits - 8, Parity - None, Stop Bits - 1,
Baud Rate 1200.
3. Set the communications software COM
port to the port number that the gauge is
connected to.
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Model CG50DL
1. Start the communications software.
2. Configure the software using the following
parameters:
Data Bits - 8, Parity - None, Stop Bits - 1,
Baud Rate 1200 (to print a report), or
9600 to transfer data file.
Note: A report can be printed to a
communications
HyperTerminal), or printed to a serial
printer using A4 or 8.5" x 11" paper.
3. Set the communications software COM
port to the port number that the gauge is
connected to.
program (i.e.