Definition:
Physical failure is not a formal term within functional safety. All failures within functional safety are either random or systematic. A “physical failure” is a loose term that means it is distinctly not a software failure. But a physical failure could be random or systematic.
We at SIL Safe do not use this term to avoid confusion.
Again, within functional safety, all failures are either systematic or random.
Key Points:
- Not a good term to use. Or at least state the failure is random or systematic.
- It’s definitely not a software failure.
- Could be random or systematic
Example:
A solenoid coil burning out suddenly is a physical failure as it is not software. But it could be systematic (a design flaw) or a random (they just do that sometimes).
See Also: random failure, systematic failure
Cited Source:
- IEC 61508-1:2010, Clause 3.6.3
- NTNU Norwegian University of Science and Technology – training slides on failure classification