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instrument parameters as well as the probe parameters, and adjust the probe zero.
First, according to the relevant industry standards or the requirements of the site, decide the test
method and choose the appropriate probe.
4.2 Zero Calibration of the Straight Beam Probe
Concerning the contact method measurement by the straight beam probe of the general flaw detector,
generally speaking, there is no emphasis on zero-bias control, as long as you aim the start pulse at the left
side line of the display grid, any zero-bias can be ignored, this is acceptable in most cases. However,
concerning the contact probe with a protective foil, owing to the time delay in the protective components,
there might be a considerable zero-bias which affects the measurement of the the distance accuracy. In order
to position the flaw to be tested, you should make a distance calibration before the measurement.
4.2.1 Calibration Procedures
In the parameter menu, set the sound velocity of the material given. If the sound velocity of the
material is unknown, you should measure the sound velocity value of the material first. (Measurement of the
sound velocity of the material)
In the parameter menu, set the sound path.
Put the probe on the calibration block (take CSK-1B) test block as an example, as shown in Figure 4-1),
the coupling is favorable.
Lock the first echo with Gate A, then adjust the probe zero submenu on the probe menu till the
measured data show the correct sound path value of the echo calibrated.
Note: the lower the sound path value is, the more accurate the calibration is.
4.2.2 Operation Steps
The instrument requires the echo with an known sound path as the calibration wave of the incident zero.
We choose the CSK-IB test block kept flat to do the distance calibration, as shown in Figure 4-1.
YUSHI INSTRUMENTS
Figure 4-1
21
Keep Calibration block flatwise
The thickness is 25mm
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