Glossary · Maintenance and diagnostics
Offline diagnosis
Also known as: Offline diagnostics
German: Offline-Diagnose
In automation and maintenance, offline diagnosis is fault diagnosis carried out while the system or item is not in normal operation, for example with the machine stopped, the device removed or on recorded data, rather than during running production.
- Maintenance
In one sentence
Offline diagnosis analyzes faults while a system is stopped, a device is removed, or on recorded data rather than during running operation.
Example
A failed servo motor is sent to the workshop, where its encoder and windings are tested on a test bench as part of offline diagnosis.
How it applies
- Maintenance: Offline diagnosis allows tests that are impossible during operation, such as insulation measurements, full function tests of a single module or step-by-step testing of a sequence.
- Engineering: Test modes, simulation and saved diagnostic data make offline analysis easier and less dependent on reproducing the fault.
- Safety: When diagnosis is done on the stopped machine, energy isolation and Lockout/tagout (LOTO) apply where hazards remain.
- Documentation: Procedures should state which state the machine must be in, which measuring equipment is needed and which safety measures apply. The documentation team should keep offline test procedures separate from checks the operator may do during operation.
Offline vs. online diagnosis
Online diagnosis runs continuously or on demand while the system operates and does not interrupt production. Offline diagnosis needs the system, or the item, out of normal operation but can go deeper.