Selecting gyroscopes requires an understanding of angular rate measurement techniques.
Optical gyros permit the reflection of a laser ray many times within an enclosure. If the enclosure rotates, the duration between the moment of laser emittance and eventual reception differs. With ring laser gyros (RLF), the laser reflection is achieved with mirrors inside the enclosure. With fiber optic gyros (FOG), the laser reflection is achieved with a coil of optical fiber.
Spinning mass gyros use a steadily-moving mass with a free-moving axis (gimbal). These gyroscopes are very fragile and require regular maintenance. When a spinning mass gyro is tilted, the gyroscopic effect causes precession – motion orthogonal to the direction tilt sense – along the axis of the rotating mass, indicating that the angle has moved. Because mechanical constraints cause numerous error factors, the axis of a spinning mass gyro is usually fixed with springs. Spring tension is proportional to the precession speed.
Vibrating gyros use micro-electro-mechanical system (MEMS) technology and a vibrating, quartz tuning-fork to measure Coriolis force. When rotated, a vibrating element (vibrating resonator) is subjected to the Coriolis Effect, causing secondary vibration orthogonal to the original vibrating direction. By sensing the secondary vibration, the gyro can detect the rate of turn.