A rate gyro is a type of gyroscope

Gyroscope

A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...

, which rather than indicating direction, indicates the rate of change of angle with time. If a gyro has only one gimbal ring, with consequently only two planes of freedom, it can be adapted for use as a rate gyro to measure a rate of angular movement.

Rate gyros are used in rate integrating gyroscope

Rate integrating gyroscope

A Rate integrating gyroscope is a rate gyro with a built in integrator. It is usually a component of an Inertial Measurement Unit or a stabilization system.-Principle of operation:...

s, and in attitude control system

Attitude control system

In spaceflight, the attitude control system or attitude determination and control system of a spacecraft consists of equipment to measure, report and change the orientation of the vehicle.- Components :...

s for vehicles, and in combination with other sensors to make inertial navigation system

Inertial navigation system

An inertial navigation system is a navigation aid that uses a computer, motion sensors and rotation sensors to continuously calculate via dead reckoning the position, orientation, and velocity of a moving object without the need for external references...

s.

The advantage of rate gyros over other types of gyros is the fast response rate and their relatively low cost.

Spinning

The traditional type of rate gyro employs relatively convention gyroscopes with viscous couplings to transfer the spin rate to allow it to be read.

Vibrating structure gyroscope

MEMS gyros are cheap and have no moving parts. They often work by sonic resonance effects driven by piezoelectric transducers, that provide a signal when a rotation occurs.