By Dovydas Kersys · Chapter 35 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.

The operator interface must reflect the actual machine. Test commands, status indications, navigation, permissions, units, setpoints and diagnostic pages.

Why this matters during commissioning

An HMI can make correct PLC logic dangerous to operate if buttons are mislabeled, units are wrong, or status colors imply the opposite state.

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Commissioning procedure

  1. Verify each major command against the intended PLC tag.
  2. Check feedback indicators independently of command buttons.
  3. Verify engineering units, decimal places and limits for setpoints.
  4. Test user levels and protected functions.
  5. Check screen navigation and maintenance diagnostic pages.
  6. Power-cycle the HMI and verify project/version and reconnection.

Common failure patterns

  • Start button writes to wrong unit/zone.
  • Green color means “commanded” on one screen and “running feedback” on another.
  • Setpoint accepts a value beyond the equipment safe range.
  • HMI shows stale data after communication loss.

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: Every command should have independent feedback. Do not let the HMI show “running” merely because a run bit was written.

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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