Measurement Computing eZ-NDT version 6.0.9 - Manual (Page 15)

eZ-NDT 938691 Investigation Mode Testing 2-9
Note: Limit bands can also be added or removed via the “Limits” selection within the Edit pull-down
menu. The difference in using the Edit menu’s “Limits” selection is that all properties (for all limit
bands) are displayed at the same time [instead of one at a time].
Note: Up to ten limit bands can exist on a plot.
13. Verify the Limits and Ranges.
a. Switch to Investigation Mode.
b. Test all the known “Pass” (Good) and “Fail” (Bad) parts. Look for consistent results.
If parts pass and fail as expected . . .
You are ready to run tests on production parts. If this is the case ensure that the “Graphical Limit
Changes are Disabled” (locked padlock) image is showing (following figure). If the padlock image is
open, click on it to lock in the limit bands at their current settings.
Graphical Limit Changes
are Disabled
If good parts fail and/or bad parts pass . . .
Are any peaks just a fraction out of range? If so, tweak those limits.
Are there peaks that you missed the first time? Add one or more limit bands.
Are there two peaks that are fairly close, one within the band and one just outside it?
Sometimes you will have 2 closely spaced peaks. These peaks will “fight” for dominance.
In this type of case you can either:
remove the entire range
widen the range to include both peaks, or
split the range with one peak in each range.
c. Re-test the known “Bad” parts. Did they all fail?
If not, consider setting amplitude limits. Sometimes, the only difference between a good and bad part
is a difference in amplitude of a significant peak.
You can change the amplitude and/or frequency limits of band by: (1) unlocking the “Graphical Limit
Changes” button, (2) placing the mouse cursor over the limit edge to be changed, (3) stretching or
shrinking the band to the desired new limit. (4) repeat steps 2 and 3 for the other limits of the band, as
desired. An example follows.