A gyro sensor or gyrometer registers or measures rotary movements .
Gyrometer is also the name for instruments used in the past for measuring the speed of rotation of rotating bodies and thus a tachometer . It was previously used to determine the speed of the drive shafts of mechanical machines .
In the usual design ("Brown gyrometer"), two masses were attached to the rotating axis, which were carried outwards by the centrifugal force during the rotation. A thread that connects both masses then shows the number of revolutions per minute on the common axis . In some constructions the masses were driven back again by their own weight , in others the elasticity of the fastening rods was used.
In many self-regulating steam engines, the steam supply was automatically regulated by such a centrifugal regulator.
Today, time measurement is far more accurate, so that the speed of rotation is measured using the number of revolutions in a period and mechanical gyrometers are practically no longer used.