Glossary · Motion control and drives
Index pulse
Also known as: Z pulse, N signal, Reference mark
German: Nullimpuls
In motion control, the index pulse is a signal that an incremental encoder outputs once per revolution (or at defined reference marks on a linear scale), used during homing to set the reference position with the repeatability of the encoder rather than of a switch.
- Motion control
In one sentence
The index pulse is an incremental encoder's once-per-revolution signal, used in homing for a precise, repeatable reference.
Example
During homing, a spindle axis moves off the reference switch and stops at the next index pulse, which fixes the zero position to within one encoder count.
How it applies
- Engineering: Because the index pulse repeats every revolution, it is usually combined with a Reference switch that selects which pulse counts. Distance-coded reference marks on linear scales let the axis find its position after a short move.
- Commissioning: If the switch edge lies very close to an index pulse, homing can land one revolution off from time to time. Shift the switch or the cam until there is enough distance.
- Operation: A missing index pulse makes homing fail or time out; it points to wiring, encoder or contamination problems.
- Documentation: Use one name for the signal throughout (index, Z, N or reference mark vary by vendor) and mention the alternatives once. Describe the homing sequence with the role of switch and index pulse.