Definitions of Jitter and Latency

In the Task Configuration object, on the Monitor tab, you can monitor the periodic jitter values of the individual tasks at runtime. Periodic jitter is distinguished from latency-based release jitter.

See the following definitions below:

Periodic jitter

Periodic jitter J_per is the deviation of the task cycle time T_per from the desired task cycle time T₀.

J_{per}=T_{per}−T_0

The desired (ideal) cycle time T₀ is specified in the configuration of the task as Interval.

In the Task Configuration editor, on the Monitor tab, you can monitor the current value as well as the maximum and minimum values of the periodic jitter at runtime.

Important

When the sum of all negative values J_per is not equal to the sum of all positive values J_per, a drift occurs.

Latency

Latency is the delay between the invocation of a task and the actual release.

Release jitter

Release jitter J_r is the difference between the maximum and the minimum latency (L) which has ever occurred.

Equation 1.

J_r=L_{\max}-L_{\min}

When L_max = L_min, a release jitter J_r of 0 results. This corresponds to a strict offset shift.