DeFelsko PosiTector 100 v.4.0 - Manual (Page 27)

100 Series Page 27
Since the substrate can often affect the return echo, all probes also provide the
user with a selection of substrate categories including concrete, wood, glass,
plastic, metal, ceramic and none to further refine the optimization.
To select these categories choose the
Setup
Application Setup menu item. Use the ↓
button
to move the highlighter down to the
Substrate:
line. A substrate list box will appear containing the
currently available list of substrates. Use the
↓ ↑
buttons located below the list box to move the
highlighter to your choice.
Now use the leftmost the
↓
button again to move the highlighter down to the
next line
Coat 1:Polymer. A coating list box will appear containing the
currently available list of coatings. Use the
↓ ↑
buttons located below the list
box to move the highlighter to your choice. Repeat for each coating layer.
S
TEP
2: O
PTIMIZE TO A
K
NOWN
T
HICKNESS
It is recommended that a known thickness of your coating be measured with the
Gage to verify the correct sound velocity constant is being used. Make sure your
coating sample is smooth. The thicker your coating “standard” the better. If you
do not have suitable check standards, see Appendix A for instructions in making
a set.
Once you have your Check Standards you are ready to optimize the Gage.
Determine the range of acceptable readings using the thickness value of the
check standard and the accuracy specification of the probe you are using.
Example: You are making a measurement of a check
standard that has been verified to be 20.0 mils
±
0.1mils. The Model 100 has an accuracy of
±
0.7
mils (
±
0.1mil + 3% of reading) at this point. The
average of several readings should fall between 19.3
mils and 20.7 mils (20.0 – 0.7 and 20.0 + 0.7 mils).
Note that the check standard has an accuracy of
±
0.1
mils and the Gage an accuracy of
±
0.7 mils. The
check standard is 7 times more accurate than the
Gage.
Select a coating from the menu that is close to your type of material. Take
several measurements on the check standard. If the average of the readings at
each point is within the tolerance for the Gage then the Gage is operating
properly within specifications and you do not need to optimize the Gage.