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mvip@mitech-ndt.com
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.
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.
4.3.3 Two Point Calibration
Note: 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.
4.4 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
