Optical

Optical-sensing technology measures absolute angular position over 360 degrees using a photoelectric device; multi-turn is achieved using internal software. Methode also uses an optical encoder concept that can detect incremental rotation of a shaft at high speeds. This can also be used for steer-by-wire applications.

At the heart of optical sensing is an opto-electrical reader. The CMOS sensor is restricted to a single row rather than a matrix. The sensor array is exposed to light through a code disc with apertures of varying sizes determined by a unique code. The aperture sizes determine a value that—when compared to a look-up table—defines angle within one revolution of 360 degrees. In our application, the sensor software detects errors very quickly and reliably. Methode's optical encoder can incrementally detect the rotation of a shaft for speeds up to 1,800 rpm with an accuracy of ±0.5 degrees. The system consists of a stationary housing containing the sensor and optical components, and a disc that attaches to the rotating shaft. Methode's system is designed to be insensitive to the axial position of the disc, while still being sensitive to radial movement.