System Reaction Time
To determine the system reaction time of any control chain, add the reaction times of all the components of the safety chain:
System Reaction Time = Sensor Reaction Time + Logix System Reaction Time + Actuator Reaction Time
System Reaction Time
Safety Task Reaction Time
The safety task reaction time is the worst-case delay from any input change that is presented to the controller until the output producer sets the processed output. To determine the safety task reaction time, use the following equation:
Safety task reaction time = (safety task period + safety task watchdog) × 1.01
The multiplier is for potential clock drift.
Safety Task Period and Safety Task Watchdog
The safety task period is the interval at which the safety task executes.
The safety task watchdog time is the maximum permissible time for safety task processing. If the time to process a safety task exceeds the safety task watchdog time, a nonrecoverable safety fault occurs in the controller, which results in a transition to the safe state (Off).
You define the safety task watchdog time, which must be less than or equal to the safety task period. You can set the safety task watchdog time in the safety task properties. This value can be modified online, regardless of controller mode, but it cannot be changed when the controller is safety-locked or once a safety signature is created.
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