8
4.4.2 Calibration to a known velocity
Notes:
This procedure requires that the operator knows the sound velocity of the material to be
measured. A table of common materials and their sound velocities can be found in Appendix A of
this manual.
①
Press the
key to activate the calibration mode. The MM (or IN) symbol should begin flashing.
②
Press the
key again, so that The M/S (or IN/
μ
S) symbols are flashing.
③
Use the
key and the
key to adjust the sound velocity value up or down, until it matches the
sound velocity of the material to be measured. You can also press the
key to switch among the
preset commonly using velocities.
④
Press the
key to exit from the calibration mode. The gauge is now ready to perform
measurements.
⑤
To achieve the most accurate measurements possible, it is generally advisable to always calibrate the
gauge to a sample piece of known thickness. Material composition (and thus, its sound velocity)
sometimes varies from lot to lot and from manufacturer to manufacturer. Calibration to a sample of
known thickness will ensure that the gauge is set as closely as possible to the sound velocity of the
material to be measured.
4.4.3 Two Point Calibration
Notes:
This procedure requires that the operator has two known thickness points on the test piece that
are representative of the range to be measured.
①
Perform a Probe-Zero.
②
Apply couplant to the sample piece.
③
Press the transducer against the sample piece, at the first/second calibration point, making sure that
the transducer sits flat against the surface of the sample. The display should show some (probably
incorrect) 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
key. The MM (or IN) symbol should begin flashing.
⑥
Use the
key and the
key to adjust the displayed thickness up or down, until it matches the
thickness of the sample piece.
⑦
Press the
key. The display will flash 1OF2. Repeat steps 3 through 6 on the second calibration
point.
⑧
Press the
key, so that The M/S (or IN/
μ
S) symbols are flashing. The gauge will now display the
sound velocity value it has calculated based on the thickness values that were entered in step 6.
⑨
Press the
key once more to exit the calibration mode. The gauge is now ready to perform
measurements within this range.
4.5 Making Measurements
When the tool is displaying thickness measurements, the display will hold the last value measured, until
a new measurement is made.
In order for the transducer to do its job, there must be no air gaps between the wear-face and the surface
of the material being measured. This is accomplished with the use of a “coupling” fluid, commonly called
“couplant”. This fluid serves to “couple”, or transfer, the ultrasonic sound waves from the transducer, into
the material, and back again. Before attempting to make a measurement, a small amount of couplant
should be applied to the surface of the material being measured. Typically, a single droplet of couplant is
sufficient.
After applying couplant, press the transducer (wearface down) firmly against the area to be measured.
The coupling status indicator should appear, and a digit number should appear in the display. If the
instrument has been properly “zeroed” and set to the correct sound velocity, the number in the display
will indicate the actual thickness of the material directly beneath the transducer.
If the coupling status indicator does not appear, not stable, or the numbers on the display seem erratic,
firstly check to make sure that there is an adequate film of couplant beneath the transducer, and that the
