Safety IO module 42: Test pulse not detected at safe output
Corrected from:
SPS release 2021 / PLC Designer 3.24
Behavior of the new version:
The default test frequency has been increased to 10/min.
Description of the behavior:
When using a safe output, the test pulses are not reliably detected. The error messages 1793 (output test pulse not detected) and 1797 (Output test pulse of low side switch timed out) occur.
Conditions under which the behavior occurs:
Using a safe output
Affected products:
Safety I/O module C25BAYA42
Short-term measures, Recommendations, Rating:
Increase the test frequency of the safe output
The safety I/O module expects a test pulse at least every three minutes. If, at a test frequency of 1/min (default) due to faults, two pulses are not detected, the module switches to the error state. If the test frequency is increased to e.g. 10/min, the probability that no pulses will be detected for such a long time is so low that it corresponds to the level of SIL 3.
