By Dovydas Kersys · Chapter 25 of 58 in Machine Commissioning.

Before you begin: Follow the machine documentation, risk assessment, site procedures and lockout/tagout requirements. Commissioning can expose personnel to electrical energy, stored pressure and unexpected motion. Never defeat a safety function merely to make a test easier. Examples and diagrams are generic and must be checked against the actual machine.

Position and speed feedback must be verified for direction, counts/scaling, index or reference behavior, and signal quality. A plausible moving value can still be the wrong sign or scale.

Why this matters during commissioning

Feedback errors can make motion control unstable or cause position errors that appear only after many cycles.

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Commissioning procedure

  1. Rotate or jog the axis a small known distance.
  2. Confirm feedback changes in the expected direction.
  3. Compare counts or engineering units with known mechanical travel.
  4. Verify index/reference pulse or absolute-position behavior if used.
  5. Inspect diagnostics for signal loss, mismatch or following error.
  6. Confirm shield/grounding and cable separation from motor conductors.

Common failure patterns

  • Motor positive direction produces negative encoder movement.
  • Incorrect pulses-per-revolution or electronic gearing.
  • Flexible coupling slips under load.
  • Noise creates intermittent count errors at high speed.

Evidence to record

  • Measured value and test point
  • Expected value / expected state
  • Observed value / observed state
  • Pass/fail result and any deviation
  • Name/date or responsible person where required

FIELD RULE: Before tuning a motion loop, prove the feedback sign and scale with a small controlled move.

Continue the series

Adapted from Machine Commissioning for Maintenance and Automation Technicians, by Dovydas Kersys. © 2026 Dovydas Kersys. Featured cover image is an AI-generated editorial illustration.

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