Magnetic Encoder

An angle sensor that uses a magnet plus a Hall or magnetoresistive chip to measure a motor shaft's rotation.

A magnetic encoder is a type of encoder (a sensor that measures rotation angle): a small radially magnetized magnet is mounted on the end of the motor shaft, facing a Hall-effect or magnetoresistive chip, and the chip reads the direction of the magnetic field to determine the angle. It's small, cheap, and unbothered by dust or oil, so it's extremely common in robot joint modules, often supplying the rotor angle needed for field-oriented control (FOC, a motor-control technique). Compared with an optical encoder, its accuracy and resolution are usually lower, and it's more sensitive to external magnetic fields and mounting eccentricity, so it needs calibration. High-end joints often place one encoder at the motor and another at the output, forming a dual-encoder setup.

ExampleMany open-source joint driver boards glue a small magnet to the end of the motor shaft, with an ams AS5047P magnetic-encoder chip soldered directly opposite it to read the rotor's angle.

Also called

Mag Encoder

Related

Rotary Encoder · Optical Encoder · Absolute Encoder · Dual Encoder · Field-Oriented Control · Hall-Effect Sensor

Sources

Rotary encoder - Wikipedia