HEIDENHAIN ND 1300 VED and Crosshair Systems - Manual (Page 110)

90 QC-300 Series User’s Guide
Probing circles
A minimum of three probed points is 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 type to the data. If the wrong feature type is assigned, it can easily be changed
by selecting the correct feature from a menu of alternatives in the DRO window.
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
window. Please refer to Chapter 13: Reference Materials for details regarding the fitting algorithms.
The View window shows the feature and the points used to define it. Errors are shown as whiskers con-
necting the probed points to the feature. The circle will be shown with data point form errors in blue and
the greatest two opposing form errors in red.
Measurement results are shown in the Features list, View window and DRO window. Results are also
shown in the DRO overlay. The feature graphic in the View window shows the feature and the points used
to define it. Errors are shown as whiskers connecting the probed points to the feature. The maximum errors
are shown in red and are used in the calculation of form. The DRO window shows the number of points
used, the radius, diameter, coordinate location of the center of the circle and the form error. 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.
Four points are probed to measure an circle
Touch the feature type... to display the menu of alternative
types
Probed points are shown in the
View window