Feature Activation And Reference Correct - Olympus EPOCH 650 User Manual

DMTA-10055-01EN, Rev. A, February 2015
attenuation and beam spread as the sound beam travels through the part. The
purpose of the DAC curve is to graphically compensate for material attenuation, near
field effects, beam spread, and surface roughness.
After plotting a DAC curve, reflectors of the same size as those used for creation of the
curve produce echoes that peak along the curve despite different locations within the
test piece. Similarly, reflectors that are smaller than those used to create the curve fall
below the level, while larger reflectors exceed the curve level.
When a DAC curve is created in the EPOCH 650 ultrasonic flaw detector, the
instrument also creates a time-corrected gain (TCG) setup. TCG is used to compensate
for the same factors as DAC, but the presentation is different. Instead of drawing a
curve across the display that follows the reference-reflector peaks downward as
sound is attenuated, the TCG setup amplifies the gain as a function of time (distance)
to bring the reference-reflectors to the same screen height (80 % FSH).
The EPOCH 650 DAC/TCG feature allows you to quickly and easily toggle between
DAC and TCG views, giving freedom to use both techniques during a single
inspection. When you switch from DAC to TCG view, the DAC curves are displayed
as TCG lines across the screen. The time-varied gain effectively amplifies the signals
across the time base to make the DAC curves appear as straight lines across the
screen.
You can customize DAC/TCG setups to your unique application requirements using
the DAC/TCG software feature for the EPOCH 650. The DAC/TCG feature
incorporates several DAC/TCG modes that adhere to ASME, ASME III, and JIS sizing
codes. The software offers direct control of gain, range, zero offset, and delay, as well
as scanning gain and transfer correction. In addition, the DAC/TCG option provides
DAC warning curves that can be customized.
In the live A-scan mode, the DAC/TCG menu contains the various setup and
adjustment parameters. These parameters provide access to several important
functions that control DAC/TCG setup and operation.
In the following sections, all DAC/TCG modes are covered. The DAC/TCG setup
procedure is the same for all modes. The setup is covered in detail in the
ASME/ASME-III section to follow. Any differences in the procedure to set up other
DAC/TCG modes are discussed in the pertinent section for that particular mode.
11.2.1

Feature Activation and Reference Correct

Before any options associated with DAC/TCG are activated, the EPOCH 650 must be
properly calibrated to the material being inspected.
Software Features and Options 227