How can industrial servo encoder signals resist electromagnetic interference?

Servo encoder signals (especially incremental ones) are highly susceptible to electromagnetic interference from motor power lines and switching noise, leading to position loss or speed fluctuations. E-Tech Electronics' comprehensive anti-interference solution employs the following: First, shielded twisted-pair cables are used to transmit the encoder signal, with the shielding layer connected to the chassis at a 360-degree angle at the driver end.

At the PCB receiver, the signal line first passes through a common-mode choke (such as CML3225A-510T) to suppress common-mode interference, then through an RC low-pass filter (R=100Ω, C=100pF) to filter out high-frequency noise, and finally connects to a differential receiver. To enhance common-mode voltage immunity, isolated encoder interface chips or optocouplers can be used. Simultaneously, a π-type filter (PWR4020R2R2M0T inductor + capacitor) is added to the encoder power supply (typically 5V or 24V). Field tests show that this solution allows for stable encoder signal reception even when the signal is routed parallel to the motor line at a distance of 10cm, with a bit error rate <10^-9, meeting the requirements for high-speed, high-precision servo applications.