DeFelsko PosiTector 100 v.4.0 - Manual (Page 45)

100 Series Page 45
Preparing Your Standards
1. Measure a suitable substrate (uncoated ) with a calibrated micrometer (
±
0.1
mil,
±
2.54 microns or better). The substrate does not have to be the same
material to which your coating will be applied. It should be smooth as
possible to give a good clean reading. The sample substrate should also be
at least four times the thickness of the coating being applied.
2. To be sure the Gage does not see the back wall of the substrate, adjust the
Gate “B” setting to be approximately two times the expected coating
thickness.
3. Coat the substrate with the material to be used to a thickness of at least 20
mils. This is required to maintain the accuracy ratio between the Gage and
the measurement capability of the micrometer.
4. Measure the total thickness of the substrate and coating with the calibrated
micrometer.
5. Calculate the coating thickness. (thickness = step 4 minus step 1)
6. Using the Model 100, measure the coating thickness.
7. Follow the procedure for adjusting the Gage (pg.26) to set the reading to the
thickness calculated in step 4. Record the sound velocity constant for your
check standards.
You are now ready to make your production measurements. The Gage has been
adjusted to the sound velocity constant needed for the specific material in use.
Periodically check your Gage with the Check Standard. If you change your
coating material you should create new Check Standards.
The above procedure will only work, using a
±
0.1mil accuracy micrometer, for
Gages designed to measure 15 mils or greater in thickness. For making Check
Standards thinner than 15 mils requires much more accurate measuring devices.
If you have multiple probes for your Model 100, you can use any probe to make
a Check Standard of greater than 15 mils, then use that Check Standard to adjust
the sound velocity constant for use at all ranges of the probes.