Encoders are widely used in machines in all industries. You can find encoders in robots, plotters, packaging machines, conveyors, automation, imaging and many more. Sometimes you cannot notice them, but they are there.
There are plenty of different technologies used in encoders, and covering all of them would be a huge topic. So, this tutorial will give a short overview regarding ones that are used most frequently. Rotary encoders.
This is a companion discussion topic for the original entry at https://community.robotshop.com/tutorials/show/encoder-basics