36
Figure 6-8 Move Gate A to Capture the Highest Reflected Echo of ¢50.0mm Hole
6.2 DAC Function
6.2.1 DAC Making
DAC (distance-amplitude curve) is used for describing the echo amplitude
variation of some regular reflector along with distance. As the sound field theory of
transverse wave is very complex and immature in flaw detection, distance-
amplitude curve is commonly used for flaw quantization and evaluation.
Two points or more is needed to make DAC and ten points at most.
The specific operation steps are as follows.
(1) Enter the DAC menu, choose DAC MODE: record.
(2) Make the probe tightly coupled on the test block CSK-
Ⅲ
A. Refer to Figure 6-9.
(3) Put probe in position 1, aim at the first datum hole(10.0mm depth ), move
probe to seek the highest amplitude (echo 1) of 10.0mm depth hole and adjust
gain to set amplitude to 80%. Move Gate A to capture the echo 1 (refer to
Figure 6-10), select DAC ECHO and press [+] key, then DAC ECHO 0
changes to DAC ECHO 1.
(4) Put probe in position 2, aim at the second datum hole(20.0mm depth ), move
probe to seek the highest amplitude (echo 2) of 20.0mm depth hole. Move
GATE A to capture the echo 2, select DAC ECHO and press [+] key, then DAC
ECHO 1 changes to DAC ECHO 2.
