A centrifuge includes a drive which revolves a rotor whose speed is controlled by a sensor located on a mounting plate which is immovably fixed in a recess of a ring installed on the mounting surface of the drive casing. The ring has a hole accommodating a movable element installed with a provision for touching over the radius of curvature upon said mounting surface of the drive casing and ensuring the movement of said ring relative to the lower surface of the rotor for installing the sensor at a certain distance from said surface at which the optimum sensitivity to the rotation speed of the rotor is ensured.
