Checkline TI-MINIMAX - Manual (Page 142)

Dakota Ultrasonics
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Good Rule of Thumb: Always look at the height of the positive and negative
cycles separately. Ask yourself if the first cycle (from left to right) is greater in
height (amplitude) than the second. If so, chances are you’ve selected the
correct phase (polarity).
If a situation does occur, as in Fig.2 above, and you’re able to notice the peak
jump during the process of loading, increasing the gain or lowering the threshold
will generally correct the error. However, if it goes unnoticed, all your
measurements will be in error. Therefore, it’s critical that the user takes the
necessary time to select the proper phase in the initial setup process.
Once again, the Auto Set feature built into the MINI-MAX will attempt to optimize
and select the polarity for you. Use of this feature is further explained in the
sections that follow.
12.8 Manually Locating the echo
The echo can be manually located by simply adjusting the delay and width
values of the MINI-MAX. While this is process is very tedious and will most often
not be used because of the
Auto Set feature, it should be explained for general
control of the instrument. The following procedures outline how to locate the
echo using delay and width.
Adjusting the Delay to Locate the Echo
Note: The delay should be adjusted to a length slightly shorter than the
physical length of the fastener. If the length of the fastener is unknown, the
user will be forced to scroll the delay until the echo is located. However, if