Ada ZCТ 777 [16/46] Zct 777

ZCT 777

MEASUREMENT FOUNDATION

ZCT 777

“Two-point calibration”

Make the rst-point calibration. But after the adjustment the required foil thickness, make two-point calibration*.

The selection of the foil: the results of the following measurements must be between values of the foil 1 and 2. The value of

the foil 2 must be in approximately 1,5 times more than the value of the foil 1.

Shot-blased surfaces

The physical nature of shot-blased 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 benet in this procedure):

Method A:

1.The gauge should be calibrated according One-point or Two point calibration. Use a smooth calibration sample with the

same curvature radius and the same substrate as the later measuring sample.

2.Now take approx. 10 readings on the uncoated, shot-blased sample to produce the mean value Xo

3.After this take approx. 10 further readings on coated, shot blasted test sample to produce the mean value Xm

4.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, where S - is the measurement uncertainty of the value Xm and Xo.

Method B:

1.Carry out a zero calibration of 10 readings on a shot-blased, 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.

2.The coating thickness can be read directly from display and should be averaged from 5….10 single measurements.