User Manual

MMS
®
Inspection DFT High 25
Calibration
7 Calibration
The coating thickness measurement is mainly influenced by the following vari-
ables:
• Physical characteristics of the base material of the sample, such as mag-
netizability (permeability) or electrical conductivity.
• The geometric shape of the sample, such as the thickness of the base ma-
terial or curvature of the sample (e.g. cylindrical shape).
• The position of the measurement location on the sample: distance from
the edge, hole, platform or step.
• Surface roughness
To ensure the coating thickness is measured correctly, the gage records the
properties of the Sample. This is done by means of a calibration (device cali-
bration based on a calibration method). The influencing variables are record-
ed using an uncoated reference part and one or two calibration foils in order
to compensate the influences for future measurements.
Please observe the following information
Make sure that the measuring point on the reference part has roughly the
same position as on the sample to be actually measured (curvature, dis-
tance from the edge, hole, platform and step).
Generally, the base material of your sample will have different material
properties than those that were taken into account in the factory calibra-
tion. For this reason, it is essential to perform the calibration with uncoated
reference parts from your own production (respect batch)! Note that a ma-
terial from different batches can have different magnetic permeabilities!
If measurements are to be performed on both base materials (magnetiz-
able, non-magnetizable), the calibration must be performed using both
base materials (FE and NF)!
Perform the calibration carefully! This is the measure for the accuracy to
which the following measurements can be performed. - Measurements can
never be more accurate than the calibration!