HEIDENHAIN ND 287 User Manual - Manual (Page 19)

ND 287
19
I – 2 F
undamentals of positioning
Incremental position encoders
Incremental linear and rotary encoders from HEIDENHAIN convert the
movements of, for example, a length gauge into electrical signals. A
position display unit, such as the ND 287, constantly evaluates these
signals and calculates the actual positions of the length gauge, which
it displays as a numerical value on the screen.
If there is a power interruption, the calculated position will no longer
correspond to the actual position of the length gauge. When power is
restored, you can re-establish this relationship with the aid of the
reference marks on the position encoders and the ND 287's reference
mark evaluation feature.
Absolute position encoders
Absolute linear and angle encoders from HEIDENHAIN transmit the
absolute position value to the position display unit immediately after
switch-on. This way the assignment of the actual position to the
position of, for example, a length gauge is re-established directly after
switch-on.
The encoder reads the absolute position information directly from the
scale graduation (see Fig. I.8), and transmits it serially to the position
display unit via the bidirectional EnDat interface.
Fig. I.7 Linear position encoder, here for the X axis
Y
X
Z
Fig. I.8 Scale grating for absolute position encoders