ABSTRACT
A mechanical rotary encoder consists of a shaft that opens and closes a switch during the rotation of the shaft. An old type of computer mouse contains two small wheels with spokes that are driven by the ball at the bottom of the mouse. A light source and detector are placed on either side of the wheel. The light detector measures how many times the light beam is broken as the wheel turns. A mechanical gyroscope consists of a spinning wheel mounted sideways on a frame. Because the wheel is spinning, its momentum resists having its orientation changed. As the instrument is rotated, the spinning wheel keeps pointing in the same direction. The angle measured is the angle between the instrument and the spinning wheel with the fixed orientation. A Microelectromechanical systems (MEMS) gyroscope is micro machined, about the size of a human hair, silicon wafer mass suspended by poly silicon springs.
