Glossary · Data, timing and communication
Latency
Also known as: delay
German: Latenz
In systems engineering, latency is the delay between an event, transmission, processing step, command, response or documentation update and the point at which it takes effect or becomes available.
- Data and interfaces
- Integrated systems
- Technical documentation
In one sentence
Latency is delay in signals, commands, responses or documentation updates; safety analyses need worst-case latency across the whole chain.
Example
From the interruption of a light curtain to the switching off of the press's safety outputs, 18 ms of latency elapse, a value that feeds into the minimum distance calculation.
How it applies
- Functional safety: Each element in the reaction chain adds latency: sensor, communication, logic, output and actuator. The sum of worst-case values determines whether a safety function acts in time.
- Integrated systems: Specify a maximum latency per interface and monitor it. Data whose latency exceeds its limit becomes stale data.
- Technical documentation: The definition deliberately includes documentation updates. Documentation latency is the delay until a change to the machine is reflected in its instructions; during that time, users work with outdated information.
Latency vs. jitter
Latency is the delay itself; jitter is its variation. Both need worst-case values in timing analyses.