Olympus EPOCH 6LT, User Interface Manual

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DMTA-10084-01EN, Rev. 2, November 2018
Chapter 11 180
This curve-height adjustment is possible because the DGS/AVG curves are calculated
based on a captured reference reflector and mathematical probe data. This allows the
EPOCH 6LT to plot the attenuation curve (in steel) for a particular reflector size
without having to acquire individual data points, as is required in a DAC/TCG setup.
This is one of the key advantages of the DGS/AVG sizing technique over the
DAC/TCG sizing technique.
To adjust the registration level
1. Open the DGS/AVG submenu, and then press the Tab key to select Reg Level .
2. Turn the adjustment knob, and then press the Enter key to adjust the current
registration-level value.
11.4.6 Relative Attenuation Measurement
There are several methods for measuring the ultrasonic attenuation within a material.
Often the procedure measures absolute attenuation in a material. This usually
requires an immersion test setup and a time-consuming set of measurements. For the
purpose of flaw sizing with the DGS/AVG method, it might be suitable in many cases
to measure relative attenuation in the test piece or calibration block as needed. This
section outlines one simple method of relative attenuation measurement, which is
generally effective. There may be a more suitable method available. You must decide
the most appropriate method to arrive at the values for ACV Specimen and ACV Cal
Block based on the application and local requirements.
Measurements:
∆ Vg = Gain difference between two successive back wall echoes (d and 2d)
∆ Ve = Gain difference on back wall curve from d to 2d
Calculations:
∆ Vs = ∆ Vg − ∆ Ve [dB]
Sound attenuation coefficient:
NOTE