Calibration is critical to any system to ensure that valid measurements are being taken. Without a new calibration scheme, only rough measurements are initially possible.
The mounting of a sphere in the chuck jaws by its stalk is feasible. However, on the NEF400, movement of the probe is only possible in the XZ axes and with motion restricted to X>0, where X=0 represents the position at the center of the chuck. Consequently, to measure four points around the equator of a sphere, the spindle must be rotated with hits taken only in the X+ direction. This means that any offset in the X direction of the probe tip from the origin is erroneously included in the computed probe tip radius.
The solution is to ensure that the hits are taken in the X+ and X- directions to cancel out the probe tip offset, which therefore obtains the correct probe tip radius. To do this, a ring or groove calibration is used instead of the standard sphere calibration.
The calibration topics are: