Abstract: A control valve having a pneumatic actuator and positioner to move the stem of a globe-type valve. The actuator has a spring-opposed piston that moves a chassis including a cam with an inclined plane. The inclination of the cam plane can be varied to precisely displace the valve stem. The amount of displacement selected, together with a specific valve plug contour, yield a specific maximum flow coefficient of the valve at that setting. The setting can be changed to accommodate moderate to very low fluid flows. A numerical display on the actuator may be used to register the flow coefficient selected.