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ZERO OFFSET: This is the method described in
ISO 19840
for
coatings
roughened by blast cleaning. The calibration uses
the smooth surface technique, and a correction
value (zero offset) is applied to each reading to
account for the effect of the roughened surface; the
value depends on the surface profile - see Table 1.
SET OFFSET: This screen sets and changes the
offset for different surface roughness This value is
used only with the Zero Offset calibration method.
Table 1: Correction values from ISO 19840
Profile according
to ISO 8503-1
Fine
Medium
Coarse
on
steel
surfaces
Correction Value
(µm) (Zero Offset)
10
25
40
Note: When the calibration method is changed, e.g.
from Smooth to Rough, the gauge will display a
message (Figure 22).
Figure 22. Recalibration required screen
If the NO softkey is pressed the CAL softkey
symbol on the Readings Screen will flash to warn
that calibration adjustment is still required.
If the YES softkey is pressed the calibration
adjustment procedure is activated - see "Calibration
adjustment procedure" on page 24.
5.2 CALIBRATION FOILS AND STANDARDS
Calibration adjustment should be carried out with
the appropriate probe on the same type of metal,
the same curvature and similar finish to the item to
be measured. It is best to use an uncoated sample
of the items to be tested.
Calibration can be carried out using measured foils
or coated standards.
R
23
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