Glossary · Data, timing and communication
Jitter
Also known as: timing jitter
German: Jitter
In systems engineering, jitter is the variation in latency or timing between repeated events or communications, such as the spread of arrival times of a cyclic message.
- Data and interfaces
- Integrated systems
In one sentence
Jitter is the variation in timing between repeated events; worst-case jitter, not the average, counts for control loops and response times.
Example
A fieldbus message scheduled every 4 ms actually arrives between 3.6 and 4.9 ms apart; that spread is the jitter the drive controller must tolerate.
How it applies
- Integrated systems: Specify both nominal latency and permitted jitter. Mixed traffic, shared networks and non-real-time operating systems increase jitter.
- Functional safety: Response-time calculations must use worst-case values. Jitter adds to the worst-case protective response time and can therefore affect the required minimum distance of a protective device.
- Control: In closed-loop control, jitter degrades stability and accuracy.
- Evidence: Measure jitter under realistic load, not on an idle test bench, and record the measurement conditions with the result.
Jitter vs. latency
Latency is the delay; jitter is how much that delay varies. A link can have low average latency and still high jitter.