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4. While the transducer is firmly coupled to the disc, press
The display will show 'Prb0' while it is calculating its zero point. When the probe zero is completed the
measurement screen is displayed.
5. Remove the transducer from the probe zero disk.
Your gauge should now be calibrated.
5.2 CALIBRATING
In order for the gauge to make accurate measurements, it must be calibrated to the sound-velocity of the
material being measured.
Different types of material have different sound-velocities. For example, the velocity of sound through steel
is 5918 m/s (about 0.233 in/µs) and the velocity of sound through aluminium is 6350 m/s (about
0.248 in/µs). 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.
There are two methods of calibrating your gauge:
Known thickness calibration: The gauge is calibrated by setting it to a single known thickness (one-point)
or two known thicknesses (two-point):
•
One-point calibration is the simplest and most commonly used calibration procedure - optimising line-
arity over large ranges.
•
Two-point calibration allows for greater accuracy over small ranges.
Known velocity calibration: The sound-velocity of the material being measured is entered directly into the
gauge.
.
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