BYK micro-TRI-gloss u Mode D'emploi page 53

17 Practical measuring suggestions
Measurement of film thickness
The film thickness sensor functions
according to the magnetic method
(Fe) or the eddy current method
(NFe). Therefore, the measure-
ment results can be distorted by
strong magnetic fields or electro-
magnetic radiation.
The measurement of film thickness
is influenced by the thickness and
magnetic (Fe) or electrical (NFe)
properties of the basis metal.
The measurement results can thus
be distorted by such factors as the
composition or heat treatment of
the substrate. It is therefore advis-
able to perform the zero calibration
on the uncoated metal which is
used for the object to be
measured.
Surface roughness also influences
the measurement of the coating
thickness. To reduce random
errors, multiple measurements are
recommended.
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If the paint film thickness is to be
measured using a magnetic back-
ground coated with a non-iron met-
al (e.g. zinc plated steel sheet), the
following must be noted:
• For the NFe setting, the
thickness of the substrate, i.e. of
the non-magnetic coating, must be
at least 50 m.
• With the Fe setting, the thickness
of the non-magnetic coating is
included in the measurement
result.