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A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analog or digital code. There are two main types: absolute and incremental (relative). The output of absolute encoders indicates the current position of the shaft, making them angle transducers. The output of incremental encoders provides information about the ''motion'' of the shaft, which is typically further processed elsewhere into information such as speed, distance and position. Rotary encoders are used in many applications that require precise shaft unlimited rotation—including industrial controls, robotics, special purpose photographic lenses,〔(【引用サイトリンク】archive-url=https://web.archive.org/web/20131005090254/http://www.canon.com/bctv/faq/rotary.html ) Canon video camera lens, used for zoom and aperture control〕 computer input devices (such as optomechanical mice and trackballs), controlled stress rheometers, and rotating radar platforms. == Encoder 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. Optical encoders are very sensitive to dust. * On Axis Magnetic. This technology typically uses a specially magnetized 2 pole neodymium magnet the same size as the motor shaft that typically requires a custom motor shaft be used. The accuracy is very bad and does not allow many resolution options. This technology does not typically offer UVW or Z pulse outputs. Due to the 2 pole magnet there is lots of jitter on the output due to the internal interpolation. * Off Axis Magnetic. This technology typically employs the use of rubber bonded ferrite magnets attached to a metal hub. This offers flexibility in design and low cost for custom applications. Due to the flexibility in many off axis encoder chips they can be programmed to accept any number of pole widths so the chip can be placed in any position required for the application. Magnetic encoders operate in harsh environments where optical encoders would fail to work. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rotary encoder」の詳細全文を読む スポンサード リンク
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