Readback Time Parameter
Each output channel has its own selectable readback time. This time specifies the maximum
duration of the turn off test for the corresponding channel and therefore also the readback
time for turning off the channel.
The following readback times can be set: 1 ms, 5 ms, 10 ms, 50 ms, 100 ms, 200 ms and
You should set an adequately high readback time if the channel involved switches high
capacitive loads. If the readback time for a controlled capacitive load is set too low, the
output channel is passivated because the discharge of the capacitance does not take place
within the turn off test.
If the readback signals are incorrect, the "short circuit" fault only causes passivation of the
output channel after the readback time elapses.
With a configured readback time of ≥ 50 ms, short-circuits (cross-circuits) can be
suppressed with an interference signal with a frequency > 10 Hz (50:50 duty cycle).
Short-circuits (cross-circuits) on an output of the same module will be detected.
Input applications of EM 4 F-DI/3 F-DO DC24V PROFIsafe
Conditions for achieving SIL/Category/PL
The table below lists the conditions which have to be met for achieving the various safety
Table 7- 28
ET 200S Distributed I/O System - Fail-Safe Modules
Installation and Operating Manual, 08/2008, A5E00103686-07
7.6 EM 4 F-DI/3 F-DO DC24V PROFIsafe digital electronic module
EM 4 F-DI/3 F-DO DC24V PROFIsafe: Conditions for achieving SIL/Category/PL
2 / 3 / d