3.
MEASURING
THICKNESS
3.1
Sound
Velocity
Calibration
In order for the gauge to make accurate measurements, it must be set to the correct sound velocity for the
material being measured. Different types of material have different inherent sound velocities. If the gauge is not set to
the correct sound velocity, all of the measurements the gauge makes will be erroneous by some fixed percentage. The
One
‐
Point
calibration is the simplest and most commonly used calibration procedure optimizing linearity over large
ranges. The T
wo
‐
point
calibration allows for greater accuracy over small ranges by calculating the probe zero and
velocity.
Note
:
One
and
Two
point calibrations must be performed on material with the paint or coating removed. Failure to
remove the paint or coating prior to calibration will result in a multi material velocity calculation that may be different
from the actual material velocity intended to be measured.
Calibration
to
a
known
thickness
Note: This procedure requires a sample piece of the specific material to be measured, the exact thickness of
which is known, e.g. from having been measured by some other means such as a caliper or micrometer.
1)
Perform a test on the built‐in test block to verify unit is functioning properly
2)
Apply couplant to the sample piece.
3)
Press the transducer against the sample piece, making sure that the transducer sits flat against the surface of
the sample. The display should show some thickness value, and the coupling status indicator should appear
steadily.
4)
Having achieved a stable reading, remove the transducer. If the displayed thickness changes from the value
shown while the transducer was coupled, repeat step 3.
（
5
）
Press the direction keys to adjust the velocity to make the actual thickness value be same with the known
value.
2.
Adjust
the
velocity
directly
if
the
material
velocity
is
known.
See
illustration
3.1:
3.1 VELOCITY ADJUSTING STEPS
