Encoders are sensors that generate digital signals in response to movement. Both
shaft encoders, which respond to rotation, and linear encoders, which respond to
motion in a line, are available. When used in conjunction with mechanical conversion
devices, such as rack-and-pinions, measuring wheels, or spindles, shaft
encoders can also be used to measure linear movement, speed, and position.
Encoders are available with a choice of outputs. Incremental encoders generate a
series of pulses as they move. These pulses can be used to measure speed, or be fed
to a counter to keep track of position. Absolute encoders generate multi-bit digital
words that indicate actual position directly