Abstract: A roundness measuring instrument of the type having a workpiece table and a pick-up carried on a pick-up mount which is radially adjustable to move the pick-up radially with respect to a fixed axis about which the table is rotatable, in which there is provided a displacement transducer sensitive to the movement of the pick-up mount in the radial direction. A device for summing the signals from the displacement transducer and from the pick-up is used to provide a wide range signal usable in metrological determinations on workpieces, such as determinations of radius and separation of two plane faces. A computer for calculating the value of a predetermined algorithm may also be provided to obviate the necessity for centering either a reference body or the workpiece with respect to the axis of rotation of the table.

Abstract: A valve for controlling an opening for the passage of fluid into and out of a pressure accumulator has a valve member, which, by the elastically expanding membrane of the pressure accumulator, can be brought against the force of a spring to a closed position. An orifice plate located in the valve housing creates a pressure difference to opposite sides of the plate, and this pressure difference is directed to opposite sides of a piston operably connected to the valve member to thereby bias the latter to the open position during outflow of fluid from the pressure accumulator, to thus prevent a premature movement of the valve member to the closed position.