How to improve interference immunity in I/O module system grounding

Improving the overall immunity of I/O module systems requires a comprehensive approach to grounding techniques. The system should employ a tree or mesh grounding structure to ensure a low-impedance path from each module to the ground. Different grounding shunt paths should be designed for different types of interference; for example, a dedicated low-inductance grounding busbar should be designed for lightning surges. An equipotential bonding busbar should be installed at the equipment inlet to connect power ground, signal ground, and chassis ground, eliminating potential differences introduced from the outside. Inside the modules, immunity is improved by placing sensitive circuits such as AIs in well-grounded areas and separating them from noise sources such as relay drives through grounding. Using common-mode chokes on all incoming and outgoing cables can suppress common-mode interference currents flowing in due to imperfect grounding. For high-frequency interference, tight-coupled signal return is achieved using a low-impedance ground plane. After the system grounding is completed, comprehensive immunity tests should be performed, such as EFT, surge, and power frequency magnetic field tests. Based on the test results, the grounding strategy should be fine-tuned, for example, by adding grounding wires or magnetic rings at specific locations to specifically improve the immunity of weak points.