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How Does An Incremental Encoder Work?

Nov,06,2019 << Return list

An incremental encoder provides a specified amount of pulses in one rotation of the encoder. The output can be a single line of pulses (an “A” channel) or two lines of pulses (an “A” and “B” channel) that are offset in order to determine rotation. This phasing between the two signals is called quadrature. 

In an incremental optical encoder, the typical assembly consists of a spindle assembly, PCB, and cover. The PCB contains a sensor array that creates just two primary signals for the purpose of position and speed. For an incremental optical encoder, an optical sensor detects light as it passes through a marked disc. The disc moves as the spindle assembly rotates and the information is translated into pulses by the PCB. For an incremental magnetic encoder, the optical sensor is replaced with a magnetic sensor and the rotating disc contains a series of magnetic poles.

Optionally, additional signals can be provided: 

An index or ‘Z’ channel can be provided as one pulse per revolution signal for homing and pulse count verification on the A and/or B channels. This index can be gated to either A or B in their various states. It can also be un-gated and vary in width.