Digital outputs, signal interruptions due to EMC interferences

Question:
What is the reason for short-term signal drops at the digital outputs X5/A1 to A4 of the 9300 devices, and how can they be avoided?

Answer:

EMC interferences:
If power and control cables are laid not in accordance with EMC requirements, EMC interferences can cause potential differences leading to leakage currents. If these leakage currents flow reverse via the driver modules of the digital outputs X5/A1 to A4, short-term signal drops can be the consequence. These signal drops have approx. 100 µs only. They can occur irregularly, according to the interference. From this sequence an oscilloscope trace can be made.
In rare cases an edge detection and possibly an oscillation evaluation of a connected control can be activated as a consequence of the short-term interruptions.
The leakage currents can be avoided by a wiring in accordance with EMC requirements. A direct-axis resistance of approx. 120 Ohm at the concerning output can additionally reduce the 'reverse current' into the digital output. This is not required in case of wiring in accordance with EMC requirements.
Detailed information about the wiring in accordance with EMC requirements can be found in article EMC basic information on controller applications in plants and machinery

Thermal overload:
Another reason for signal drops at the digital outputs can be a thermal overload of the driver modules, which is caused by impermissibly high output currents > 50 mA. In this case the signal interruption takes much longer (4-5 ms). After a transient response these signal interruptions repeat regularly (ca. 250 Hz). The output currents are to be reduced to values under 50 mA in order not to overload the output driver modules (external resistance min 480 Ohm and 24 V).