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Chapter 3. Making Measurements
3.8.1
Recording the DAC Curve
DAC Curve points are typically recorded from a standard with equally-sized reflectors (holes) located at various material depths. The
primary echo from each of these points, for a total of up to 16 echoes, are recorded. When DAC mode is active, the instrument displays a
line that represents echo peaks for constant reflectors at varying material depth. This line is drawn as either a curved, linear in gain, line
based on a series of collected DAC points or a series of straight line segments that join these DAC points. Only one DAC curve can be
stored at a time. To program the DAC curve proceed as follows:
1.
In the ACQUIRE menu, activate the DAC/TCG submenu using the joystick (
2.
Couple the probe to the first reference point and use the GATE A START function to adjust Gate A so that it is broken by the primary
echo. If necessary, use the Gain Toggle to adjust the gain so that the echo crosses Gate A, and the highest peak in Gate A is at
approximately 80% of full-screen height. The highest peak must not be higher than 100% full-screen height.
Note: The AUTO 80 function allows for automatic application of gain to set the Gate A triggering echo to 80% of full screen height.
3.
While Gate A is lined up over the first reference echo, use the joystick (
center of the joystick (
the first DAC Curve point, which is then treated as the reference echo. The amplitude value at which this point is recorded becomes the
"reference amplitude" value. However, the "reference amplitude" is updated if a new point is recorded with an earlier TOF.
84
) to activate the function. When the value of the RECORD function changes from 0 to 1, you have recorded
).
) to select the function titled RECORD. Press the
USM Go Operator's Manual
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