Abstract: In a turntable device for measuring angles of lock of a steerable wheel of an automobile, the spindle of the turntable is coupled to an angular displacement pickup carried by a movable arm or the like which is subjected to the translational displacements of the turntable. The movable arm or another part which is associated with the turntable and accompanies this latter in its translational displacements is equipped with a detection element placed opposite to a stationary zone having physical characteristics (such as electrical conductivity, reflecting power, etc.) which are different from those of the zone support. The function of the zone surface is virtually to materialize the freedom of displacement conferred on the turntable by its mode of assembly. The detection element is connected into an electric circuit for controlling a visual signal element or a system for stopping the measuring apparatus associated with the angular displacement pickup of the device.