Fig. 28 Worst-Case Reaction Time - Beckhoff EP1957-0022 Operating Instructions Manual

Operation
Fig. 28: Worst-case reaction time
This assumes that a signal change occurs at the sensor and is transmitted to the input. A communication
error occurs at precisely the moment when the signal is to be transferred to the communication interface.
This is detected by the logic following the watchdog time of the communication link. This information should
then be transferred to the output, but a further communication error occurs here. This error is detected at the
output following the expiry of the watchdog time and leads to the switch-off.
This results in the following equation for the worst-case reaction:
ReactionTime = WD +
max Comm
with, for example
ReactionTime = 15 ms + 15
max
44
WD + RT
Comm Actuator
ms + 20 ms = 50 ms
Version: 2.0.0 EP1957-0022 and EP1957-2222