How do incremental encoders work?！

An Incremental rotary encoder is also referred to as a quadrature encoder. This type of encoder utilizes sensors that use optical, mechanical or magnetic index counting for angular measurement.

How do Incremental Encoders Work?

Incremental rotary encoders utilize a transparent disk which contains opaque sections that are equally spaced to determine movement. A light emitting diode is used to pass through the glass disk and is detected by a photo detector. This causes the encoder to generate a train of equally spaced pulses as it rotates. The output of incremental rotary encoders is measured in pulses per revolution which is used to keep track of position or determine speed.

A single-channel output is commonly implemented in applications in which direction of movement is not significant. Instances in which direction sensing is important, a 2-channel, quadrature, output is used. The two channels, A and B, are commonly 90 electrical degrees out of phase and the electronic components determine the direction based off the phase relationship between the two channels. The position of an incremental encoder is done by adding up all the pulses by a counter.

A setback of the incremental encoder is count loss which occurs during power loss. When restarting, the equipment must be referenced to a home position to reinitialize the counter. However, there are some incremental encoders, like those sold at Anaheim Automation, which come equipped with a third channel called the index channel. The index channel produces a single signal pulse per revolution of the encoder shaft and is often used as a reference marker. The reference marker is then denoted as a starting position which can resume counting or position tracking.

NOTE: Incremental rotary encoders are not as accurate as absolute rotary encoders due to the possibility of interference or a misread.

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