A yaw-rate sensor is a gyroscopic device that measures a vehicle’s angular velocity around its vertical axis. The angle between the vehicle's heading and vehicle actual movement direction is called slip angle, which is related to the yaw rate.
In the piezoelectric type, the sensor is a "tuning fork"-shaped structure with four piezo elements (two on top and two below). During straight ahead driving, the upper ones produce no voltage as no Coriolis force acts. But in cornering, the rotational movement causes the upper part of the tuning fork to leave the oscillatory plane creating an alternating current voltage which is proportional to the yaw rate and oscillatory speed. The output signal's sign depends on the direction (left or right).
In the micromechanical type, the Coriolis acceleration is measured by a micro-mechanical capacitive acceleration sensor placed on an oscillating element. This acceleration is proportional to the product of yaw rate and the oscillatory velocity, which is maintained electronically at a constant value.
A yaw-sensor is needed for Electronic stability control.
Yaw rate sensors are used in aircraft and in the electronic stability control systems of cars.