13
3.
Apply a drop of couplant on the transducer and place the
transducer as shown in diagram.
Note: Disregard the value displayed; it is not important. What is
important is accurately performing these steps to ensure reliability
of the zero calculation.
4.
Select MENU/PROBE/ZERO TRANSDUCER and press ENTER.
The ZERO TRANSDUCER screen is displayed.
5.
Press OK (or ESC to cancel).
When the manual probe zero is completed the measurement
screen is displayed.
6.
Remove the transducer from the probe zero disk.
Your gauge should now be zeroed.
7.3 CALIBRATING - FOR A MATERIAL
Sound travels through different materials at different speeds, and in
order to measure these materials accurately the correct sound velocity must be programmed into
the gauge. There are three methods of calibrating the gauge.
Known Material Calibration
- The material to be measured is selected from a list in the gauge.
Known Velocity Calibration
- If the material sound velocity is known this may be entered manually
into the gauge.
Known Thickness Calibration
- A sample of the material to be inspected is measured using
alternative means and then used to calibrate the gauge.
•
One Point
calibration is the simplest and most commonly used calibration procedure with best
performance over large measurement ranges
•
Two Point
calibration uses two samples of different thicknesses, with enhanced accuracy over
small ranges close to the sample thicknesses used
For the highest measurement accuracy use the known thickness calibration as this takes into
account variation in material composition, temperature and a variety of other factors.
Note: If you create a completely new setup for interface-echo (I-E) mode, a two point calibration
must be performed.
7.3.1 Known Material Calibration
If the material velocity is unknown, and a sample thickness cannot be taken from the material, you
can choose a material type from a list stored in the gauge. For each material stored in the list there
is a corresponding velocity value.
Note: These velocities will not always be an exact representation of the material being tested. Use
these values only if a close approximation is acceptable.
1.
Select MENU/CAL/MATERIAL and press ENTER.
2.
Scroll through the material list until the appropriate material is highlighted
3.
Press ENTER to select the material type followed by OK.
Press MEAS to return to the measurement screen.
To achieve the most accurate measurements possible, it is generally advisable to 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.
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