Magnetic Encoders

A magnetic encoder is an electromagnetic mechanical device that detects the distance between two or more magnetic poles in order to detect the position of a rotating shaft. They are also available as magnetic linear encoders for precision position feedback in applications such as woodworking, stone cutting, sawing, packaging, and automation and assembly systems.
Magnetic encoders are usually intended to operate in harsh environments while providing precise measurements. They tend to operate on the Hall Effect or the Magnetoresistive Effect. The Hall Effect is a physical phenomenon where a voltage (called the Hall Voltage) can be produced in electrical conductors and semiconductors because of charge carriers being forced in a direction perpendicular to a magnetic field. The Magnetoresistive Effect is a property where the electrical resistance of a conductor or semiconductor changes in the presence of a magnetic field.
Because these effects can occur in semiconductors, single chip magnetic encoder chips are available for rotational or linear measurement systems. Encoder chips using anisotropic magneto resistive (AMR) technology are quite common and low cost. Transmission of the positional data can be done with a serial interface (for example I2C) or as a pulse width modulated (PWM) waveform.
Very low-cost Hall Effect sensors are also available that can be used as position detectors when being used in conjunction with magnetic poles in a system that move relative to the sensor. As the sensors are usually converted to a digital value by an integrated analog to digital converter (ADC), they are usually specified as having a maximum sample rate and a bit resolution.
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