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Pros and Cons of Absolute vs. Incremental Rotary Encoders

From POSITAL - FRABA

An incremental encoder simply generates pulses proportional to the position. The principle of the incremental measuring system is the scanning of a line pattern on a glass or plastic disc (see Image 1). An optoelectronic component converts the line pattern (transparent or not transparent) into electronic pulses, e.g. transparent equals 5V and not transparent equals 0V. This reflects the binary value "1" and "0". Depending on the direction of rotation an electronic counter ads or subtracts the signals while the disc is turning. The current count is stored in an electronic buffer and is available for further evaluation. However, this method has some serious disadvantages. In an incremental encoder the pulses generated are counted in a counter and at power loss it will lose the count and consequently you will have to home the machine before you can start the operation. Also, an incremental encoder is generally more susceptible to electrical noise. Image 1: Incremental Disc Applications with higher requirement regarding precision often rely on absolute rotary encoders. Especially when it is complicated or not possible at all to return to the reference point.
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Products & Services
Absolute Rotary Encoders
Absolute rotary encoders use optical, mechanical, or magnetic indexing for angular measurement. They do not lose their position after power-down, but instead provide absolute position upon power-up without requiring a home cycle or any shaft rotation.
Incremental Rotary Encoders
Incremental rotary encoders are multi-turn sensors that use optical, mechanical, or magnetic index-counting for angular measurement. They contain no absolute reference, but instead count relative to the turn-on position.
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