Aktek AT300 Panduan Pengguna - Halaman 10

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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

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/μS) 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 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

key to adjust the displayed thickness up or down, until it