Pulse output only, or by logically relating the reference pulse to the A and B data channels.
Thus pulse it is most frequently used in positioning and motion control applications as an electronic starting point of known position from which counting or position tracking begins.
In long travel or multiple turns of the encoder, the reference pulse is sometimes
used by the control to initiate an electronic check on the total count received from
the encoder. For example, each time a reference pulse is received by the control, the
total count received from channels A and B should be an even multiple of the
encoder's pulses per revolution.
Ballscrew Position Table Example
In motion control encoder applications,a PLC, CNC, or motion controller wlll usually command a sequence of moves with each axis of a positioning system to bring the table to the same starting position before beginning a task.
The following is a typical automatic referencing and backlash compensation requence for establishing a home position through the use of an encoder marker pulse.
1. If the Home Switch is open (indicating a pos1tion on the positive side of home)
when the command is received, the axis is accelerated in the negative direction at
the JOG ACCELERATION rate and moved at the FAST JOG VELOCITY until
the Home Switch closes.
Note that a mechanical home-position limit switch is usually not repeatablv
accurate enough for this application. The encoder reference or marker pulse has
much greater repeat accuracy and is therefore a better reference point to estab
lish a starting point for subsequent measurements. The home limit switch is used
to signal the control that the next marker pulse signal received is "Home”in
multi-turn encoder applications.
2. The axis is stopped at the JOG ACCELERATION rate.
3. The axis is accelerated in the positive direction at the JOG ACCELERATION rate and moved at the FAST JOG VELOCITY until the Home Switch opens.
4. The axis is accelerated in the negative direction at the JOG ACCELERATION rate and moved at the SLOW JOG VELOCITY until the Home Switch closes and an encoder marker pulse is sensed by the control (in that order).
5. The axis is stopped at the JOG ACCELERATION rate.
Transducer Operating Speed
All transducers have inherent mechanical and electronic speed limitations, and
exceeding them may result in incorrect data or prematl!re failure. The maximum
operating speed for a given application will be the maximum electronic operating
speed of the encoder and the electronics to which it is connected, or the encoder's
maximum mechanical RPM specification, whichever is less.