Encoder selection is one of the more error-prone replacement decisions because two encoders that look identical can have different output protocols, different resolutions, and different power requirements. The part number encodes all of this, and a "close enough" substitute usually fails to communicate with the controller.
Specs to confirm before ordering:
- Type: incremental (A/B/Z pulses) or absolute (position-on-power-up via serial or parallel interface)
- Resolution: PPR (pulses per revolution) for incremental; bits per turn and turn count for absolute (e.g., 17-bit single-turn + 12-bit multi-turn)
- Output signal: TTL (5 V), HTL/push-pull (10–30 V), RS-422 differential, SSI, BiSS-C, EnDat 2.2, HIPERFACE, Profinet, EtherCAT, CANopen
- Supply voltage — 5 V, 10–30 V, or specific to the OEM
- Shaft type: solid shaft (with bellows or flex coupling required), hollow-shaft, hub-shaft, blind hollow
- Shaft diameter or bore diameter
- Mounting: synchro flange, clamping flange, square flange, servo flange
- IP rating, especially for direct outdoor or washdown mounting
- Cable or connector style (M12, M23, MS, flying leads)
Common gotchas: incremental encoders with TTL output running on a 24 V machine bus require level shifters or HTL versions — direct connection damages the output stage. Absolute encoders with multi-turn count via gear (mechanical multi-turn) require power to retain count, but battery-backed multi-turn loses count when the battery dies during long shutdowns. Hollow-shaft encoders need a torque arm or anti-rotation pin; without it the encoder body spins with the shaft and shears the cable. Coupling alignment on solid-shaft encoders is critical — misalignment over time destroys the bearings.
Typical applications: motor feedback for servo and VFD vector control, conveyor speed and position feedback, length measurement on cut-to-length lines, indexing table position, and CNC axis feedback. For legacy machines, exact OEM encoder replacement preserves the signal type, resolution, and mechanical interface the controller expects.
For obsolete encoders, send the OEM part number for a sourcing quote.
