No, the calibration on the flat plate causes a systematic measuring error on a curved surface. This means the measuring values will be too large. This is because the instrument rates the measuring signals of the sample (here: the curved object) in such a manner, as if they were from a flat sample.
Some reasons could be: Did I choose the correct driver unit with relevant administrator rights? Was the right interface chosen, in the software on the PC? (also see device manager)
The accuracy of measuring instruments is ensured by the calibration standards. The calibration must be carried out on real, uncoated samples. Furthermore one must take care to measure on the same measuring positions. It is important to take enough measurements in order to receive a significant mean value.
One checks the calibration by remeasuring the calibration foil on the uncoated sample. It has to be this measuring position, where you measure lateron as well. Fischer Base calibration plates are not useful for this purpose.
Here various measuring versions are possible:
With the phase sensitive eddy current method one can measure nonferrous metals on ferrous metals, for example Zinc on Fe. Also nonferrous metals on non-conductive plastics may be measured, such as Copper on Iso. Another possible example is Nickel on Copper for the case of ferrous metals on nonferrous metals.
The amplitude sensitive eddy current method measures electrically non-conductive coatings on electrically conductive, non-magnetizable substrates, such as anodized coatings on Al, lacquer on copper, lacquer on Al and ceramics on Ti.
The magnetic inductive method measures non-magnetizable coatings on well-magnetizable substrates, such as Zinc on Ferrous or Lacquer on Ferrous.
The measuring accuracy for FISCHER tactile instruments is dependant on factors such as coating thickness, surface condition, utilized probe a.s.o. Details for accuracy and repeatability under ideal conditions can be taken from the technical probe datasheets.
One has to definitely calibrate on the real, relevant parts with an identified coating thickness. The magnetizability of nickel coatings may differ strongly, i.e. there may occur strong differences between the magnetizability of the measured parts opposed to the calibration parts. This can lead to measurement errors. Especially in the field of incoming inspections, problems may then arise.
It measures all magnetizable phases in steel, such as Deltaferrite, Martensite. This implies, that the measurement values for Deltaferrite are systematically too high, if any further magnetizable metal phases are in the steel. This fact needs to be considered in advance.