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6.3Changing Calibration - Acoustic Velocity IsNot Known
In applications where the type of material is not known or the material is
not listed in the Acoustic Velocity Table, the following procedure can be
used to calibrate the gauge for highest accuracy.
1. Obtain a sample of the material with a known thickness or use a
micrometer, caliper or similar device to accurately measure it.
2. Turn on the gauge by pressing the key.
3. Place a small amount of coupling fluid on the sample of known
thickness and place the probe on the sample. The Stability Indicator
should have nearly all its bars illuminated. Having achieved a stable
reading remove the probe from the sample.
4. Press the key.
5. The units of measure indicator “IN” or “MM” will be flashing
indicating that you are in the Measurement Calibrationmode.
(The other calibration mode is the Acoustic Velocity Calibration mode,
as described in section 6.2, which is used to adjust the acoustic
velocity to another known value.)
6. Use the and keys to adjust the displayed measurement
value to match the thickness of the known sample. By pressing and
holding the key, the numbers will change more rapidly.
7. Press the key again and the acoustic velocity units indicator
“IN/µs” or“M/s” will be flashing showing the acoustic velocity
value that was calculated for this sample. If desired, record this
value so it can be re-entered easily in the future.
8. Press the key again to exit the calibration mode and return to
the measurement mode.
Note:If the key is pressed while in the calibration mode, the
TI-25M will be reset to the factory default calibration for common steel
(0.2330 IN/µs or 5920 M/s).
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