Industrial Engineer · phase 6 of 16
Diagnostic Buffer / Fault Log
Time-ordered record of controller, module, and network events used for troubleshooting.
The Explain card
- Plain English
- The diagnostic buffer is the controller's diary. Faults, mode changes, module failures, network drops and power cycles land in it with a timestamp, newest first.
- Example
- A machine stopped at twelve minutes past three in the morning and nobody saw why. The buffer shows a remote rack connection lost a minute earlier and a major fault two seconds after that, which points at a cable rather than at the program.
- Why it matters
- It is the only witness that was awake. Read it before you touch anything, and check the controller's clock, because a log with the wrong time tells a convincing wrong story.
- Hook
- The machine keeps a diary, and it is worth reading.
Where it sits in the deck
Phase 6: PLC Operating Modes, Safety, and Diagnostics
Run, program and fault: what a controller does when something goes wrong, and the safety functions that decide how much that costs.
