Dac/Tcg - Epson USN 52R Operating Manual

DAC/TCG

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