Industrial Engineer · phase 6 of 16 · noun
Major Fault
Serious controller or program fault that can stop task execution or place the controller in a faulted state.
The Explain card
- Plain English
- A major fault is a problem serious enough that the controller stops executing logic. Outputs go to their fault state and the fault light comes on.
- Example
- A routine indexes past the end of an array. The controller faults, the line stops, and the fault log records the type, the code, and which routine did it.
- Why it matters
- A major fault is a hard stop on the whole machine, so a bug that would be harmless on a laptop takes production down. Fault handlers can catch some kinds and let the controller continue, which is a choice that has to be made on purpose.
- Hook
- The controller would rather stop than guess.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
The technician read the Major Fault code after a watchdog timeout and checked the controller task configuration before attempting a restart.
Why these words
- major Latin maior, greater marks the higher level of severity
- fault Old French faute, failing or deficiency names the detected condition
Where it came from
- Origin
- English phrase combining major, from Latin maior, with fault, from Old French faute and Latin fallere
- Entered the language
- 20th century
- What changed
- Major broadened from greater size or rank to greater severity, while fault developed from deficiency or blame into a technical label for an abnormal condition.
How it is spelled
- Pattern
- Major uses j for the sound /dʒ/.
- Pattern
- Fault retains the written -ault sequence.
- Breaks the pattern
- The l in fault is not pronounced in many English accents.
Spelled like
- majority
- default
- assault
- vault
Broken into chunks
-
major
- majority
- major
-
fault
- faulty
- default
What it sits beside
Same subject
- minor fault
- watchdog timeout
- controller status
- fault handler
Same shape
- major alarm
- minor fault
- critical error
controller fault terms
- Major Fault
- minor fault
- recoverable fault
- nonrecoverable fault
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.
