HEIDENHAIN ND 1300 OED and Crosshair Systems - Manual (Page 82)

64 QC-300 Series User’s Guide
Probing arcs
A minimum of three probed points is required to measure an arc. 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 the arc is less than 185 degrees, Measure Magic will correctly recognize the arc and assign the cor-
rect feature. However, when the arc is 185 degrees or more, it is likely that Measure Magic will assign the
circle feature type to the data. If the arc is shallow, Measure Magic might mistakenly assign a line feature.
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.
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 arc 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 Feature list, View window and DRO window. The DRO window
shows the number of points used, the radius and diameter of the arc, the coordinate location of the center
of the arc and the form error. 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. 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 an arc
Touch the feature type... to display the menu of alternative
types
Probed points are shown in the
View window