Mar 5 2009
Fischer Instrumentation (GB) Ltd has developed a simple stand that offers enormous benefits to anyone who has had variable results trying to measure the coating thickness on a small curved component with a standard probe.
This is because probes are designed to give their best performance on flat surfaces and only when they are positioned correctly. Curved surfaces make it difficult to hold the probe exactly perpendicular to the surface and it is very difficult to make the measurement on exactly the same spot every time.
Typically probes will give a 10% error on bars that are less than 18 mm in diameter. This is just due to the distortion of magnetic fields or eddy currents generated by the probe. Errors for the same reason are incurred if the item is too small or too thin. (Typically a flat area less than 8 mm or component thickness less than 0.2 mm).
These errors, however, can be minimised and the best performance obtained from the probe if a simple measuring stand is used. This ensures the positioning is always the same, the angle of approach is perfect and the pressure constant. Using the stand shown in the images, the scatter of measurements is improved by a factor of ten (standard deviation improvements from 0.4mm to 0.04mm).
A measurement stand will de-skill the operation, increase the throughput of measurements and give much more consistent results.