HEIDENHAIN ND 760 E - Manual (Page 11)

11
Position encoders
The position encoders on the machine convert the movements of the
machine axes into electrical signals. The ND display unit evaluates these
signals, determines the actual position of the machine axes, and displays
the position as a numerical value.
If the power is interrupted, the relationship between the machine axis
positions and the calculated actual positions is lost. The reference marks
on the position encoders and the REF reference mark evaluation feature
enable the ND to quickly re-establish this relationship again when the
power is restored.
Reference marks
The scales of the position encoders contain one or more reference
marks. When a reference mark is crossed over, a signal is generated
which identifies that position as a reference point (scale datum =
machine datum).
When these reference marks are crossed over, the ND's reference
mark evaluation feature (REF) restores the relationship between axis
slide positions and display values which you last defined by setting the
datum. If the linear encoders have distance-coded reference marks,
you need to move the machine axes a maximum of only 20 mm to do
this.
Y
X
Z
Workpiece
Position
encoder
Scale in Distance-coded
linear encoder reference marks
Reference marks
Fundamentals
Bateil1.pm6 21.01.2002, 09:39 11