By Dovydas Kersys · Chapter 37 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.
Trends and diagnostic timestamps are powerful commissioning tools. They reveal short events that technicians cannot observe manually, such as voltage dips, sensor chatter, speed overshoot or sequence timing races.
Why this matters during commissioning
If PLC, HMI, drives and SCADA use different clocks, event reconstruction becomes unreliable.
Commissioning procedure
- Verify controller, HMI, drives and data systems share an appropriate time source where designed.
- Trend critical analog values, sequence steps, alarms and drive data during startup.
- Use adequate sample rate for the event being investigated.
- Capture before changing parameters so the original behavior is preserved.
- Save representative good-run trends as a future maintenance reference.
Common failure patterns
- Trend sample rate too slow to catch a 100 ms sensor pulse.
- HMI clock differs from PLC by minutes.
- Trend scales hide oscillation.
- Only failed traces saved; no known-good comparison exists.
Evidence to record
- Time-source settings
- Clock offsets
- Trend configuration
- Saved baseline traces
- Observed event timing
FIELD RULE: When a fault is faster than your eyes, trend it before guessing.
PART VII
Utilities and Process Controls
Utilities and Process Controls
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Adapted from Machine Commissioning for Maintenance and Automation Technicians, by Dovydas Kersys. © 2026 Dovydas Kersys. Featured cover image is an AI-generated editorial illustration.