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EPOCH 4PLUS
9.4.4.2 JIS
The Japanese Industrial Standard DAC curve setup and functionality is identical to the
standard DAC/TVG functionality described in Section 9.2. The only modification in
Advanced DAC/TVG to the JIS function is the capability of toggling between a DAC and
TVG view. However, only the main DAC curve is viewable in TVG mode.
9.4.5 20%-80% DAC Option
The Advanced DAC/TVG software incorporates a combination of the DAC curve and
TVG techniques using the 20%-80% DAC option. For most sizing and inspection codes
that use a DAC curve, the inspector cannot interrogate a potential defect that does not rise
above 20% of FSH. In the past, scanning gain is added to inspect these defects that appear
further into a part and only reflect below 20%. Necessary gain adjustment is then noted to
calculate the flaw size.
The 20%-80% DAC feature takes advantage of the TVG functionality of Advanced DAC/
TVG to create a DAC curve that only falls between 20% and 80% screen height. Any echo
that falls below 20% FSH during setup has 12 dB added to it automatically. A new DAC
curve section starting at 80% FSH is created. This setup divides the screen into 12 dB
DAC Gain regions. The DAC Gain is displayed based on the location of the gated echo in
time.
Figure 48 DAC Gain
To activate the 20%-80% DAC option, follow the steps below:
1. Select 20-80% from the ADV. DAC/TVG option in the Options Menu by highlighting
the function and pressing [ENTER].
2. Use the RIGHT and LEFT slewing keys to capture the first echo of the desired DAC
curve and press the DRAW DAC key [F1].
3. Continue using the RIGHT slewing key to capture the next desired DAC curve echo,
and press the DRAW DAC key [F1] to capture successive points. Any point that is
captured below 20% of screen height will automatically be raised by 12 dB and the
DAC curve will continue to draw from 80% FSH downward. A dashed vertical line
indicates the point where gain adjustment begins within a particular screen range.
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