The rotary encoder detects the magnetic field of a permanent magnet attached to the end of the rotating shaft using CMOS magnetic sensors (MAGFET arrays) set in a square arrangement. The rotation angle is calculated in real time by logic circuits integrated with the sensor arrays. Using a fine-pitched sensor array and a digital domain signal processing technique, a compact encoder with high resolution can be realized. A prototype sensor chip with dimensions of 4.3 x 4.3 mm2 is implemented. The CMOS rotary encoder can achieve the resolution of 10 bits per rotation.
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| Block diagram of sensor chip | Arrangement of sensor chip and permanent magnet |
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| Prototype Sensor chip | |