rate gyro
Original archive entry. The text, images and links below are kept as they were written.
A gyroscope with one free gimbal axis ( precession axis ) . Motion around this axis is constrained by a spring. The second gimbal axis is tied to the spacecraft. An angular motion of the spacecraft around this axis produces an angular excursion of the precession axis against the spring force; the angle of excursion is proportional to the rate of angular rotation in radians per second.