Benefits and drawbacks of the most important encoder systems

Encoder system

Advantages

Disadvantages

Incremental encoder

  • Robust designs
  • Long cable lengths of up to 300 m are possible with TTL and HTL interfaces
  • Wide range of resolutions, mounting positions, and interfaces
  • Very high resolution possible
  • Built-in encoders: motor-integrated, compact design possible
  • If a voltage drop occurs, the position information is lost.

Absolute encoder

  • Position information is still available even after a voltage drop and restart
  • Very high resolution possible with sin/cos interfaces
  • Single-turn encoder design: A unique position within one motor revolution is determined.
  • Multi-turn encoder design: In the case of rotary encoders, a position must also be determined over several revolutions.
  • Higher costs

Resolver

  • Robust design
  • Insensitive to vibration and temperature
  • Resolvers by SEW‑EURODRIVE are single-turn encoders
  • High evaluation effort

An important criterion when selecting an encoder is the robustness of an encoder system. As some encoders are installed directly on the motor, they must be insensitive to temperature and vibration, otherwise the encoder could be damaged.

An encoder system's susceptibility to interference also plays a major role. In the event of a supply voltage failure, the absolute encoder retains its current path information, while the incremental encoder loses it. As a result, the absolute encoder is also resistant to external interference pulses. Once the interference fades away, the device continues to work flawlessly since the saved path information has not been changed.

In the incremental encoder, a lost or excess counting pulse is not registered and leads to a permanent measurement fault.