ElektroPhysik
E-11
5.
Calibration
In order for the MINITEST 403 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. For example, the velocity of sound through
steel is about 5920 m/s (0.233 inches-per-microsecond),
versus that of aluminum, which is about 6350 m/s (0.248
inches-per-microsecond). 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 two- point calibration allows for greater accuracy
over small ranges by calculating the probe zero and
velocity.
The MINITEST 403 provides three simple methods for
setting the sound-velocity, described in the following
pages.
5.1
Calibration to a known thickness
Note:
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.
1.
Make sure the MINITEST 403 is on.
2.
Perform a Probe-Zero (see section „Probe Zero“)
3.
Apply couplant to the sample piece.
4.
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 (probably incorrect) thickness value,
and the Stability Indicator should have nearly all
its bars on.
5.
Having achieved a stable reading, remove the
transducer. If the displayed thickness changes
from the value shown while the transducer was
coupled, repeat step 4.
Calibration
