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Chapter 8
Reference
Three non-collinear points are the minimum required to measure a circle. Up to
100 points can be probed during a circle measurement. Use more points for
greater accuracy. Every point on a circle is weighted equally but the first three
points are used to estimate the form. Space the first three points widely to ensure
an accurate form estimate.
The QC200 applies a mathematical algorithm to the probed points. The algorithm shifts the circle around until its circumference is as close to every point as
possible. Further shifting to better accommodate a few points leads to greater
distances from other points.
In the illustration below circle 1 shows three points distributed around a theoretically perfect circle. Given perfect geometry there is little need to worry about
probing additional points. In real life applications, geometry is never perfect. A
more realistic circle is represented by circle 2. Clearly three points are insufficient
to measure circle 2 accurately.
Probe more than the three required points to average out inconsistencies in the
geometry. For example, a circle with rough edges is difficult to measure accurately without probing additional points.
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