Encoders vs. Resolvers: Position Sensing Compared

Two different technologies for measuring the same basic thing: exactly how far a shaft has turned.

An encoder (optical or magnetic) converts rotational position into a digital or analog electrical signal directly. A resolver is an older, electromechanical alternative — essentially a small rotating transformer — that produces an analog signal requiring more complex electronics to decode into a position reading.

Why resolvers still show up

Resolvers are more tolerant of extreme heat, vibration, and electrical noise than most encoders, which is why they're still common in demanding industrial and aerospace applications despite needing more complex supporting electronics. In humanoid robotics, encoders are far more common, since the operating environment is generally less extreme and cost/simplicity matter more.

What actually matters in practice

For most robotics applications, resolution (how finely position can be measured) and update rate matter more than the encoder-vs-resolver distinction itself — a coarse, slow position sensor will limit control performance regardless of which underlying technology produced the reading.