-Take readings by placing the probe on the coating to be measured and
raise it after the beep. The reading is shown on display.
NOTE
:
-Apply the probe to test sample several times.
-The thickness of the foil should be roughly equivalent to the estimated
coating thickness.
-Even while a series of measurements is being taken, foil calibration can
be carried as often as necessary. The old calibration will be overwritten;
the ZERO calibration remains in memory until make the zero point
calibration.
-See one-point calibration for more information.
4-2-4.Shot-blased Surfaces
The physical nature of shot-biased surfaces results in coating thickness
reading that are too high. The mean thickness over the peaks can be
determined as follows (not that the statistics program is of great benefit
in this procedure):
Method A:
-The gauge should be calibrated according to 4-2-2 or 4-2-3. Use a
smooth calibration sample with the same curvature radius and the same
substrate as the later measuring sample.
-Now take approx. 10 readings on the uncoated, shot-biased sample to
produce the mean value Xo.
-After this take approx. 10 further readings on coated, shot blasted test
sample to produce the mean value Xm
-The difference between the two mean values is the mean coating
thickness Xeff over the peaks. The greater standard deviation s of the
two values Xm and XO should also be taken into consideration:
Xeff=(Xm-Xo)±S
Method B:
-Carry out a zero calibration of 10 readings on a shot-biased, uncoated
sample. Then carry out a foil calibration on the uncoated substrate.
The foil set should consist of a number of individual foils of max.
50 microns thickness each and should roughly correspond to the
estimated coating thickness.
-The coating thickness can be read directly from the display and should
be averaged from 5 .... 10 single measurements. The statistics function
is useful here.
Method c:
This method also gives reliable results. Simply follow the two-point
calibration method using two foils as described in section 4.2.3. For a
maximum approach to the respective nature of surface, the foil value can
