Glossary · Maintenance and diagnostics
Fault isolation
Also known as: Fault localization
German: Fehlerlokalisierung
In maintenance and diagnostics, fault isolation is the part of fault diagnosis that identifies the faulty item down to the replaceable unit, such as a module, cable, sensor or board.
- Maintenance
In one sentence
Fault isolation narrows a detected fault down to the specific faulty item, such as a module, cable or sensor, that can be repaired or replaced.
Example
By swapping the encoder cable and watching whether the error follows it, the technician isolates the fault to the cable rather than the drive.
How it applies
- Engineering: Designers support fault isolation with channel-level diagnostics, test points, LEDs, clear labeling and a modular structure that matches the spare parts.
- Maintenance: Technicians follow a sequence of checks, often splitting the signal path in halves, until the faulty item is found. The target level (module, board, component) depends on the service concept.
- Operation: Fast isolation shortens downtime and reduces unnecessary part replacement.
- Documentation: Isolation procedures should be written as numbered steps with expected results and a branch for each outcome. The documentation should reference the exact Spare part number of the item that is identified, and wiring diagrams must use the same designations as the labels on the machine.
Fault isolation vs. fault detection
Fault detection tells you that a fault exists. Fault isolation tells you which item to repair or replace. In safety engineering, "isolation" can also mean separating energy sources, which is a different concept; see Energy isolation.