Test 1, two results:
Size error on a sphere, tactile
The PSize value expresses the error when measuring the size of a geometry, specifically the diameter of a sphere. It is calculated as the difference between the diameter of a least squares sphere, deduced from 25 points measured, and the calibrated diameter of the sphere (Figure 1.3).
Form error on a sphere, tactile
This test, based on the preceding one, establishes the distribution of contact (tactile) measurements over a sphere. 25 points are probed on a calibrated sphere, and a least squares sphere is derived from these 25 points. The test result is the thickness of a shell encompassing the 25 points, the center of which is the least squares sphere (Figure 1.4). This process has to be repeated for two positions of the sphere within the volume of the measuring arm. The worse of the two results is used.