Specifications

13. Calibrating for Digital Measurement
USN52 L Operating Manual Page 81
11. Adjust the MTL VEL until the displayed S= value matches
the known thickness (or flaw distance) of the test block:
12. Optimize the reference echo that represents the lower end
of the expected measurement range. Check to assure that
the correct echo appears within the gate and has sufficient
amplitude to exceed threshold level. If necessary, adjust
GAIN.
NOTE: If you are using multiple backwall echoes to cali-
brate, adjust a-START to the left so that the multiple that
represents the lower limit of the measurement range is the
first echo in the gate.
13. While the probe is coupled, adjust ZERO until the displayed
S= value matches the known thickness (distance) of the test
block:
NOTE: Adjusting ZERO changes the horizontal position of
displayed echoes (and DAC/TCG curve). It has no effect
on gate position or DELAY setting.
14. Repeat steps 6 through 13 until no further calibration is
needed.
15. Recheck the position and width of the gate to assure that
echo signals from the smallest and greatest expected mea-
surements will occur within the gate. If necessary, adjust a-
START and a-WIDTH until these conditions are met.
The next illustration shows a typical A-scan and measurement line
display for 0 TO 1st measurement with a delay line probe.
13.4 0 TO 1st - Dual Element Probe
Because multiple echoes do not typically occur with dual element
probes, 0 TO 1st mode must be used for thickness or distance to
flaw digital measurement.