Industrial Engineer · phase 6 of 16 · noun

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 are logged 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.

Word knowledge

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

During commissioning, the engineer opens the Diagnostic Buffer after an ET 200SP input module drops offline and checks the earliest timestamped entry.

Why these words
  • diagnostic Greek diagnostikos, able to distinguish modifies buffer by identifying its troubleshooting purpose
  • buffer English buffer, originally something that cushions a blow serves as the head noun and names the storage structure
Where it came from
Origin
a modern English compound combining Greek-derived diagnostic with English buffer
Entered the language
20th century
What changed
Diagnostic moved from distinguishing diseases to identifying technical conditions, while buffer expanded from a cushioning device to reserved computer storage.
How it is spelled
Pattern
diagnostic ends in the adjective-forming suffix -ic
Pattern
buffer preserves the doubled f of buff before the suffix -er

Spelled like

  • automatic
  • electronic
  • buffered
  • buffering
Broken into chunks
  • diagnostic
    • diagnose
    • diagnosis
  • buffer
    • buffered
    • buffering
What it sits beside

Same subject

  • fault code
  • module diagnostics
  • alarm history
  • event timestamp

Same shape

  • diagnostic message
  • diagnostic register
  • receive buffer

controller troubleshooting records

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.

Neighbours in this phase