Rotary encoder vs. Linear encoder！

There are two basic geometries for encoders: linear and rotary. Rotary and linear encoders work in similar ways. As the names imply, linear encoders measure motion along a path, and rotary encoders identify rotational motion. Thus the application determines which encoder is best suited for the job.
A linear encoder typically consists of a scale (a coded strip) and a sensing “head” that reads the spacing between the scales’ coding to determine position. A linear encoder’s resolution is measured in pulses per distance (pulses per inch (ppi), pulses per millimeter, etc.). The scale (coded strip) has a set resolution with marks embedded into it or on it, which is read by the head. A linear encoder with 100 ppi resolution would read 100 marks for every one inch of movement.
Unlike linear encoder resolution measurement, rotary encoder resolution is measured in pulses per revolution (PPR), also known as “line count.” A rotary encoder is commonly comprised of an internal coded disc and a sensing head used to read rotary position. A linear encoder is very similar to a tape measure, while a rotary encoder is more like a measuring wheel. A rotary encoder with 100 ppr resolution would read 100 marks on its coded disc for every revolution.

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