Epson USN 52L, USN 52R manual Dac/Tcg

DAC/TCG Operation

5.4 DAC/TCG

The DAC/TCG function enables you to:

•record a Distance-Amplitude Curve and to store it as an essential part of the current data set.

•display the Distance-Amplitude Curve (DAC) of the reference echoes.

•activate the Time-Corrected Gain (TCG) which increases the gain as a function of distance so that all reference echoes attain the same height. The amplitude evaluation of echo indications is now carried out in relation to the first reference echo.

•activate the TCG as above, however, with simultaneous representation of the DAC/TCG function.

Due to the angle of beam spread of the sound beam and the sound attenuation in the material, the echo height of equally sized reflectors depends on their dis- tance to the probe.

The DAC/TCG in the USN 52R/USN 52L can correct these influences.

In this regard, the gain is varied as a function of the time of flight in such a way that the echoes appear equally high on the display irrespective of their dis- tance.

This means that the echo amplitude now only depends on the reflection characteristic of the flaw.

If you use a calibration block provided with artificial flaws corresponding to the natural flaws of your test object for recording the DAC, you can use this echo amplitude for the evaluation of the reflector without having to make any other corrections. The calibration block should be made of the same material as the test object.

Each artificial flaw is scanned, the echo is peaked and then recorded.

The DAC brings the echo sequence to 80% screen height. During this, the instrument sets the gain to the gain value of the highest echo.

The maximum dynamic range is 40 dB;

the maximum slope of the curve is 6 dB/µs; the maximum number of curve points is 9.

Krautkramer USN 52R/USN 52L Issue 05, 02/00 5-25