Encoders implemented using a variety of technologies！

Encoders may be implemented using a variety of technologies:
• Conductive. A series of circumferential copper tracks etched onto a PCB is used to encode the information. Contact brushes sense the conductive areas. This form of encoder is now rarely seen except as a user input in digital multimeters.
• Optical. This uses a light shining onto a photodiode through slits in a metal or glass disc. Reflective versions also exist. This is one of the most common technologies.
• Magnetic. Strips of magnetised material are placed on the rotating disc and are sensed by a Hall-effect sensor or magnetoresistivesensor. Hall effect sensors are also used to sense gear teeth directly, without the need for a separate encoder disc.

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