Incremental vs absolute encoder: which one to buy
“Encoder” on a purchase order is not enough. Incremental units report pulses and lose position at power-off unless the axis homes. Absolute units keep position (single-turn or multi-turn). The nameplate string — ERN vs EQN, DFS vs AFM, bits vs PPR — decides the spare.
Request a quoteHow to tell incremental from absolute
- 1
Read the type, not the marketing name
Heidenhain ERN / EQI (incremental) vs EQN / ECN (absolute). Sick DFS60 (incremental) vs AFM60 / SKM36 (absolute). Tamagawa TS5214 is typically incremental; serial Yaskawa units on Sigma motors are often absolute.
- 2
Look for PPR versus bits
PPR or “lines” usually means incremental. Bit count (13-bit, 17-bit, 2048×4096) usually means absolute. Do not order a 2048 PPR incremental unit to replace a 2048-line absolute encoder.
- 3
Match the output protocol
TTL / HTL / 1 Vpp are common on incremental. EnDat, SSI, BiSS, Fanuc serial, and Yaskawa serial are absolute or OEM-closed. Protocol mismatch will not commission.
- 4
Send both plates if the encoder is inside a motor
Yaskawa, Fanuc, and Mitsubishi motors often hide the real feedback OEM. Photograph the motor and the encoder cap.
When incremental is the right spare
Simple axes that home on every start, conveyors, and many packaging machines use incremental feedback. Replacement still needs matching PPR, voltage, output, bore, and connector — not “any incremental encoder.”
When you must keep absolute
CNC axes, robots, and hoists that cannot re-home after a power cut need the same absolute protocol and bit count. A cheaper incremental encoder will run the axis into a crash or refuse to enable.
Incremental vs absolute FAQ
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