Positioners are used to control the opening or closing of theelectrical or pneumatic signals. These .
Control valve opening or closing is usually done automatically by electrical, hydraulic or pneumatic actuators
Sliding-stem globe Control Valve
Angle Control Valves
control signals normally based on 3-15psi (0.2-1.0bar), more common now are 4-20mA signals for industry, 0-10V for HVAC systems, and with the help of “Smart” systems, HART, Fieldbus Foundation, and Profibus being the more common protocols