An encoder is a device used to change a signal (such as a bitstream) or data into a code. The code may serve any of a number of purposes such as compressing information for transmission or storage, encrypting or adding redundancies to the input code. translating from one code to another. This is usually done by means of a programmed algorithm, especially if any part is digital, while most analogue encoding is done with analog circuitry.
Examples:
a Compressor is used to encode data into a smaller form.
a multiplexer combines multiple inputs into one output.
a rotary encoder is a sensor, transducer for converting rotary motion or position to a code of electronic pulses.
a linear encoder is a sensor, transducer or readhead paired with a scale that encodes position. The sensor reads the scale in order to convert the encoded position into an analog or digital signal, which can then be decoded into position by a digital readout (DRO). Motion can be determined by change in position over time. Linear encoder technologies include capacitive, inductive, eddy current, magnetic, and optical. Optical technologies include shadow, self imaging and interferometric. Linear encoders are used in metrology instruments and high precision machining tools ranging from digital calipers to coordinate measuring machines.