The servo encoder cable is the “sensory nerve” of the motion control system, ensuring distortion free transmission of millivolt level differential signals in strong electromagnetic interference and high-speed motion.
Its precise structure includes multiple layers of shielding, twisted signal lines, and dynamically optimized conductor arrangements to resist interference and maintain electrical stability.
The handling of connection points and mechanical durability design jointly ensure reliability in millions of bending cycles, directly determining system accuracy and response speed.
The encoder signal is extremely weak, extremely fast, and extremely afraid of interference. If the encoder cable is not twisted or shielded, the servo will lose steps, shake, and sound an alarm.
1.Why do encoder cable have to be twisted pair cable?
The encoder outputs differential signals (A, A -, B, B -).
● Two wires twisted together, external interference will be added to both wires simultaneously and equally.
● The differential receiver only looks at the difference between two lines, and interference is directly cancelled out.
The consequences of not using twisted pair cables for encoder cables:
● Interference is directly superimposed on the signal.
● Servo counting error, inaccurate position, shaking, and runaway.
2、 Why does the encoder cable need a shielding layer?
The encoder signal is a small voltage, high-frequency pulse, and very fragile:
● Servo drives, frequency converters, and motor wires are all sources of strong interference
● The shielding layer shields the electric field and electromagnetic radiation from the outside
The consequences of not having to block:
● Communication loss and error (ALE, encoder failure) at high speeds
● When the machine tool/equipment moves, its position drifts
3、 A brief summary
● Twisted pair=anti common mode interference
● Shielding layer=anti external electromagnetic interference
● Servo encoder=weak signal+high speed+high precision
The combination of the three is not optional, but necessary for shielded twisted pair cable.
When choosing encoder cables, in addition to choosing shielded twisted pair cable, we also need to consider whether to choose high flexibility cable or ordinary encoder cables based on the usage environment. If the encoder cable is installed in a drag chain, we must choose high flexibility encoder cable or drag chain specific encoder cables.
