910-269-EN, Rev. B, June 2011
228 Chapter 11
To adjust the registration level
Choose 7/7 > DGS > Reg. Level to adjust the current registration-level value.
11.3.6 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
conditions to measure relative attenuation in the test piece or calibration block as
needed. This section outlines one method of relative attenuation measurement that is
simple and has been found to be generally effective. There might be more suitable
methods available. You must decide the most appropriate method to arrive at the
values for AcvSpecimen and AcvCalBlock based on the application and local
requirements.
Measurements:
∆ Vg = Gain difference between two successive back-wall echoes (d and 2d)
∆ Ve = From DGS/AVG diagram. Gain difference on back wall curve from d to 2d
Calculations:
∆ Vs = ∆ Vg - ∆ Ve [mm]
Sound attenuation coefficient: α = ∆ Vs / 2d * 1000 [dB/m]
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