How to eliminate common-mode interference in motion controller MC encoders

The key to eliminating common-mode interference (CM) in motion controller encoder signals lies in suppressing its flow path. Use common-mode chokes, such as the CML series, on the encoder differential signal lines, which offer high impedance to common-mode noise. Connect a small-value Y capacitor in parallel between the signal line and controller ground to provide a local discharge path for high-frequency common-mode noise. Employ isolated interfaces, such as isolated encoder receiver modules or optocouplers, to break ground loops.

Use shielded twisted-pair cables and ensure the shield is properly grounded. Check the ground potential difference between the encoder and controller; if it is excessive, improve the system grounding. For single-ended encoder signals, convert them to differential transmission before connecting them to the controller. Use a differential receiver with a high common-mode rejection ratio at the controller receiver. Test the system's counting stability by injecting common-mode interference into the encoder cable to verify the effectiveness of the elimination measures. Eliminating common-mode interference is crucial for improving encoder reliability in harsh industrial environments.