DeFelsko PosiTector 100 v.4.0 - Manual (Page 15)

100 Series Page 15
Gage is set to its maximum 5 coats. The
5 largest peaks are displayed on the
left. However a 6
th
layer interface exists
at 6.9 mils (from the surface) as
measured by the CURSOR.
Once you have checked Gage operation on a known thickness of material and
have modified current Application settings to most closely match your
coating/substrate combination you are ready to measure. Be sure to apply
sufficient couplant to fill voids in the surface and to fully wet the probe tip.
Multiple measurements in the same location may require additional couplant
every so often. Hold the probe steady when measuring and release the probe
switch after hearing the double BEEP. Leaving the Graphics Mode turned on
helps you to understand what the Gage sees and how it arrived at a thickness
measurement.
Never rely on a single measurement. It is important that several measurements
be consistent and repeatable, or as repeatable as your application will allow. If
the coating or substrate is rough or curved, use Statistics Mode to determine the
average of a series of readings. Comparing a series of averaged results will often
provide acceptable repeatability where individual readings might not.
Don’t be too quick to adjust a displayed reading to reflect what you believe the
coating thickness to be. Even though another measurement method might report
a different thickness, it is better to leave the Gage at its default settings and
evaluate repeatability first. The last step in any measurement application is
optimization using the
Setup q
q Adjust Reading / Adjust Velocity
menu option.
Whenever you run into difficulty, be sure to stop and
measure your Check standards, the plastic shims or
some other part you previously had success measuring.
Once you have made sure you are operating the Gage
correctly and that it is performing properly, return to
your application. Verify the settings found in
Setup
Application Setup. Then select Setup q
q
Gate/Zoom Control and, between
measurements, change Gate A and B values to observe
the reflected echoes. Use the cursor to measure peaks
not measured by the Gage (measured peaks have a
black triangle beside them).
To measure properly, the ultrasonic echo must pass completely through the coating(s),
reflect off an acoustically dissimilar material such as the substrate or other coatings, and then
return unimpeded to the probe tip. Sometimes the coating is not homogeneous; it contains
solids or uncured sections that dampen or deflect the echo. Sometimes the interface between
coatings and the substrate is not distinct; the two materials have blended to create a
“transition” layer. Also the material may either be too thin or acoustically too thick or
attenuative to measure with an ultrasonic technique.