Siemens describes incremental encoders as providing delta position or angular signals and absolute encoders as providing an actual position value after power-on. Reference requirements depend on whether the controller retains position and on the specific encoder system.
An encoder can report movement as increments or provide a position value within its measurement range. Siemens’ glossary and motion-control material describe the key difference and the effect on a reference run.
Encoder comparison chart
| Check | Incremental encoder | Absolute encoder |
|---|---|---|
| Position information | Incremental delta position or angular signals | Actual position value |
| Power-on behavior in Siemens’ description | A reference point may be needed when the controller has not retained position | Position is available after the encoder supply is switched on |
| Main system check | Count handling, reference strategy and controller retention | Encoder code, resolution and controller protocol support |
Siemens notes that in its described motion-control case, an incremental system generally needs travel to a reference point after power-off because position is not usually stored in the controller. Absolute encoders can provide the actual position after power-on. Encoder interfaces and retention options differ, so use the exact encoder and drive manuals.
For motor selection context, read servo vs stepper motors. Browse motion control.
Sources
Common questions
What does an incremental encoder report?
Siemens describes incremental encoders as providing delta position or angular signals.
What does an absolute encoder report at power-on?
Siemens describes an absolute position encoder as providing the actual position after its supply voltage is switched on.
Does every incremental encoder require a reference run?
No universal rule is stated here. Siemens notes that a reference run may be needed when the controller does not retain position through power-off.