HEIDENHAIN MANUALPLUS 620 - Page 51

51
Encoders
Overview
For speed and position control of the axes and spindle,
HEIDENHAIN offers both incremental and absolute encoders.
Incremental
encoders
Incremental encoders have as measuring standard a grating
consisting of alternate lines and spaces. Relative movement
between the scanning head and the scale causes output of
sinusoidal scanning signals. The measured value is calculated by
counting the signals.
Reference mark When the machine is switched on, the machine axes need
to traverse a reference mark for an accurate reference to be
established between measured value and machine position. For
encoders with distance-coded reference marks, the maximum
travel until automatic reference mark evaluation for linear encoders
is only 20 mm or 80 mm, depending on the model, or 10° or 20°
for angle encoders.
Evaluation of refer-
ence marks
The routine for traversing the reference marks can also be started
for specific axes via the PLC during operation (reactivation of
parked axes).
Output signals
Incremental encoders with sinusoidal output signals with ~ 1 V
PP
levels are suitable for connection to HEIDENHAIN numerical
controls.
Absolute
encoders
With absolute encoders, the position information is contained
in several coded tracks. Thus, an absolute reference is available
immediately after switch-on. Reference-mark traverse is not
necessary Additional incremental signals are output for highly
dynamic control loops.
EnDat interface The MANUALplus 620 features the serial EnDat 2.2 interface
(includes EnDat 2.1) for the connection of absolute encoders.
Note: The EnDat interface on HEIDENHAIN encoders differs in
its pin assignment from the interface on Siemens motors with
integrated absolute ECN/EQN rotary encoders. Special adapter
cables are available.
Encoder inputs
Incremental and absolute linear, angle or rotary encoders from
HEIDENHAIN can be connected to all position encoder inputs of
the controller unit.
Incremental and absolute rotary encoders from HEIDENHAIN can
be connected to all speed encoder inputs of the controller unit.
Input frequency
1)
Channel inputs Signal level/
Interface
1)
Position Speed
Incremental signals
~1 V
PP
33 kHz/350 kHz 350 kHz
Absolute position values
Incremental signals
EnDat 2.2
2)
/02
~1 V
PP
–
33 kHz/350 kHz
–
350 kHz
Absolute position values EnDat 2.2
2)
/22 – –
1)
Switchable
2)
Includes EnDat 2.1