How to ensure EMC for long-distance pulse transmission in motion controllers (MC)

To ensure the EMC performance of long-distance transmission of motion controller MC pulse signals, a robust transmission scheme is required. Differential transmission standards, such as RS-422, are preferred due to their strong common-mode rejection capability. Matching resistors, typically 120Ω, should be installed at both ends of the cable. Shielded twisted-pair cables should be used, with the shield grounded at the controller end. If the remote device is also grounded, a ferrite core should be added to the cable to suppress ground loop current.

A common-mode choke should be added to the controller output port. For single-ended pulses, current loop transmission, such as 0-20mA, can be used. Multi-level protection circuits should be implemented at the port to handle lightning strikes. The pulse rise time should be controlled to prevent excessive high-frequency radiation. Isolators are recommended for pre-transmission isolation. Cables should be laid separately from power cables, maintaining a minimum distance of 30cm. For extremely long distances, repeaters or fiber optic converters can be used. Testing should be conducted to verify that the waveform quality of the transmitted pulses and the system's radiated emissions meet standards.