HEIDENHAIN ND 1400 - Manual (Page 66)

52 QC-300 Series User’s Guide
Probing circles
A minimum of three probed points are required to measure a circle.
There is no practical limit to the number of points that can be probed,
and in general accuracy is increased by probing more points.
When 185 degrees or more of the circle is probed, Measure Magic will
correctly recognize the circle and assign the correct feature. However,
when less than 185 degrees is probed, it is likely that Measure Magic
will assign the arc feature to the data. If the wrong feature type is as-
signed, it can be changed by selecting the correct feature from a menu
of alternatives in the DRO screen.
A best fit algorithm is used to define the circle when more than three points are probed. The circle fit to the
probed data can also be changed by selecting the desired fitting algorithm from a menu in the DRO screen.
Please refer to Chapter 12: Reference Materials for details regarding the fitting algorithms.
Measurement results are shown in the Feature list, View screen and DRO screen. The feature graphic in
the View screen shows the feature and the points used to define it. Errors are shown as whiskers connect-
ing the probed points to the feature. The maximum errors are shown in red and are used in the calculation
of form. The DRO screen shows the number of points used, the radius, diameter, coordinate location of
the center of the circle, form error reference frame and the projection plane. When only three points are
probed, the form error is zero. When more than three points are probed, the form error is the sum of the
two greatest opposing error magnitudes.
In this example, three points are
probed to measure a circle
Touch the feature type... to display the menu of alternative
types
Probed points are shown in the
View window