DeFelsko PosiTector 100 v.4.0 - Manual (Page 25)

100 Series Page 25
The need to optimize is dependent upon a number of factors. If you are using
standard materials in your coatings and can select from the menu there is
probably no reason to optimize the Gage. On the other hand, if you need very
accurate measurements and are using non-standard materials it is suggested that
you optimize the Gage to your coating material prior to making actual
measurements.
Check standards may be made following the instructions given in Appendix A.
If you already have samples with a known thickness of your coating material
you may optimize the Gage to them. Review the material in Appendix A to
determine if your sample was measured to a sufficient accuracy for valid
optimizations.
Calibration
To calibrate the Model 100 you must have a set of Thickness Calibration
Standards. These Standards should have 3 to 5 values that cover the full range of
the probe being used. These standards must have been measured to an accuracy
that is four times or better than the accuracy of the Gage at the thickness being
measured. For example if the Gage has an accuracy at the measurement point of
±
2 microns then the standards have to have been calibrated or verified to an
accuracy of better than or equal to
±
0.5 micron. Thickness Calibration
Standards are available from your dealer for each of the Model 100 probes. They
come complete with a certificate of calibration showing traceability to NIST.
Once you have Thickness Calibration Standards you can calibrate the Gage. Be
sure to use the correct sound velocity constant. Make several readings from each
of the standards. If the average of the readings at each point is within the
tolerance for the Gage for that standard then the Gage is operating properly
within specifications and you are finished the calibration.
If the Gage is not within tolerance, first verify that your standards are good and
then repeat the measurements. If the Gage is still found to be out of tolerance
you may want to try a second set of standards. If after this step the Gage is still
reading out of tolerance you should return it for service. There are no user
alignments available.
E
FFECTS OF
T
EMPERATURE
Variations in temperature change the sound velocity of materials and transducer
delay tips. If measurements will be made in extreme hot or cold temperatures,
prepare and measure your Check Standards (see Appendix A) in the working
environment. The Model 100 should then be optimized using these Check
Standards in the same environment.