ALTANA Micro-Gloss Manual - Manual (Page 26)

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6.3 Measurement of film thickness
The film thickness sensor functions according to the
magnetic method (Fe) or the eddy current method
(NFe). Therefore, the measurement 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 advisable to perform the
zero calibration on the uncoated metal which is
used for the object to be measured.
Surface roughness also influences the measure-
ment of the coating thickness. To reduce random
errors, multiple measurements are recommended.
If the paint film thickness is to be measured using a
magnetic substrate coated with a non-iron
metal (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 µm.
• With the Fe setting, the thickness of the non-
magnetic coating is included in the measurement
result.
Measurement techniques