4.7. - Cut Points
The angles -90° and +270° are at the same
position on a circle, but if a motor in spec is sitting at 0°, it
will move counter-clockwise by 90° to get to the -90°
position and clockwise by 270° to get to the +270° position.
By setting a lower cut point for a particular motor, you can
choose what value on the circle the four-circle
angle calculations will produce.
That is, the calculations will place the angle between the lower cut point
and that value plus 360°.
Cut points can be set for the  ,  and  four-circle angles.
For the 2 angle, the lower cut point is fixed at -180°.
For the
azimuth-fixed modes, there is pseudo-cut point for the azimuthal angle.
If the cut point is less than zero, the
calculated azimuth will be between -180° and 0°,
otherwise the azimuth will be between 0° and +180°.
The default cut points are shown below.
| Angle |
Default Cut Point |
|
| |
-180 |
| |
-180 |
| |
-180 |
 |
0 |
The macro
cuts
can be used to set or display the cut points.
With no arguments, it displays the current cut points.
Two arguments are used to set a single cut point.
Four arguments set all cut points.
1.FOURC> cuts
Cut Points:
th chi phi azimuth
-180 -180 -180 0
2.FOURC> cuts phi 90
or
3.FOURC> cuts -180 -180 90 0
4.FOURC>
|
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