DMTA-10084-01EN, Rev. 2, November 2018
Chapter 11
186
11.5.3 Calculating A and C Values
When a gated echo whose peak is below 100 % FSH is present, the EPOCH 6LT
automatically calculates the A and C values necessary to provide a D indication rating
value. For the A value, the EPOCH 6LT automatically calculates the required dB value
to bring the gated echo to reference height. To calculate C, the EPOCH 6LT uses the
data in the sound path calculator to generate an attenuation factor.
For this calculation to be accurate, you must enter the correct thickness for the test
piece.
You can save the data for this discontinuity in the EPOCH 6LT data logger. For
general data logger information, see “Data Logger” on page 101.
At the bottom of an ID saved with the AWS D1.1 feature activated, you can see the
values for A, B, C, and D. This data can be viewed in the file review window.
You can also choose to see live A, B, and C values displayed in the reading
measurement boxes at the top of the screen.
While using the EPOCH 6LT and the AWS D1.1 software feature, you must account
for any inspection conditions that could cause variations in the displayed indication
rating (D value), and properly interpret the meaning of echo indications and reported
D values corresponding to these indications.
11.6 Back Wall Echo Attenuator
The back wall echo attenuator (BEA) option enables you to apply an independent gain
level to the A-scan defined by the gate 2 start position and width. Using the BEA, you
can reduce the amplitude of the back wall echo when high gain levels are used to find
small flaws.
The BEA option is commonly used with two specific forms of inspection:
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