Specifications

13. Calibrating for Digital Measurement
Page 78 USN52 L Operating Manual
13.2 0 TO 1st - Single Element Contact Probe
0 TO 1st mode can be used for measuring either thickness or
distance to flaw. Calibration requires a test block of the same
material, velocity of sound, and temperature as the material to be
measured. Precise thickness or distance to artificial flaws must be
known.
Use the following procedure to calibrate in 0 TO 1st mode, using a
single element contact probe.
1. Calibrate the A-scan display according to Sections 9.2 and
9.3. Use the same test block for both A-scan and digital
calibration.
2. Set MEASURE function (lower level) to 0 TO 1st:
, or , or ,
3. Select the GATE menu: , or
4. Adjust a-START to place the leading edge of the gate bar
slightly to the left of the horizontal position in the A-scan that
corresponds to the smallest measurement to be taken:
5. Adjust a-WIDTH to place the trailing edge of the gate bar
to the right of the horizontal position that corresponds to the
greatest measurement to be taken:
6. Couple the probe to the test block and optimize the refer-
ence echo (backwall, flat bottom hole, etc.) that represents
the upper limit of the expected measurement range.
7. Use GAIN to adjust the reference echo amplitude to a suit-
able level:
NOTE: If you are using multiple backwall echoes to cali-
brate, temporarily adjust a-START to the right so that the
multiple that represents the upper limit of the measurement
range is the first echo in the gate.
8. Adjust a-THRESH, gate threshold level:
For flaw applications, set level based on desired alarm sensi-
tivity relative to flaw size.
For thickness measurement, set level just high enough to re-
main above nonrelevant indications.
9. Select the S-CAL menu:
10. Observe the S= value in the measurement line and obtain a
stable reading.
If desired use the enlarged display:
or