Dakota Ultrasonics MINI--MAX - Manual (Page 145)

MINI-MAX Ultrasonic Bolt Tension Monitor
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If the threshold level were increased in the NO GATE diagram, so that the level
was higher than the amplitude of the noise (A), the MINI-MAX would have
detected on the correct reflection (C). Alternatively, if the gain level was
decreased, the signal amplitude of the noise (A) would have decreased below
the threshold level, and the MINI-MAX would have also detected the correct
reflection (C). This example brings all the fine adjustments into consideration,
and demonstrates the importance and versatility of having fully functional scope
available.
Now, let’s look at the diagrams again but in a slightly different way. Let’s look at
the case of a potential mode conversion issue. Let’s assume that (A) is the
actual true reflection off the end of the bolt, and the MINI-MAX is detecting on the
echo at (B). However, the signal has a horrible first cycle and is relatively week.
But as we look further out in time or length, the second mode conversion
reflection (C) looks like a much cleaner signal to use. Now refer to the W/GATE
diagram. By activating and setting the start time of the GATE (B), we can force
the MINI-MAX to use the mode conversion reflection (C), instead of (B). Once
again, the same gain and threshold tools can be use for fine adjustment signal
optimization.
Adjusting the Gate using the Hot Menus
1) Press the MEAS key once to activate measure menu items. Press the
MEAS key multiple times to move right and the ESC key multiple times
to move left until the GATE cell is highlighted.
2) Press the UP, DOWN, LEFT, and RIGHT arrow keys to scroll the
highlighted value.