Mechanical Encoders

A mechanical encoder is an electromechanical device that converts position or movement into a signal or signals that can be read by an electronic circuit or processor system. There are two main types of mechanical encoders. Rotary encoders detect position or movement by converting the angular position of a shaft. Linear encoders are 'read-heads' that encode position associated with a scale, and are uncommon as other technologies like 'optical' and 'magnetic' encoders are better suited for applications where linear encoders would be used (for example CNC Mills and Gantry Tables').
Mechanical Rotary Encoders have a metal disc containing several concentric rings that are fixed on an insulator and connected to a shaft. Sliding contacts wipe against the metal disc making contact to the disc as the concentric rings rotate around with the shaft. This causes a positionally encoded 'conduction' pertaining to the pattern of the rings. Mechanical encoders have rings that encode the positional information in a binary or binary coded sequence on a parallel set of output terminals. Binary coded decimal and gray codes are common coded output patterns.
In some cases, gearing is used to turn the encoder into a 'multi-turn encoder'. Some encoders are battery powered, and some use the energy of the rotation to generate the electrical power required to output the positional signal or even store the number of turns in an integrated memory device. Mechanical encoders are highly prone to wear, and, as a result, are not very common today. They are still used in applications like the volume control of a stereo or the tuning of an FM Radio.
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