Positioners are most commonly used to move a control valve to a specified position so that a process meets specific parameters (flow, pressure, temperature). Fisher™ positioners have the reputation of providing the most accurate, robust and reliable performance in the industry.
Valve positioners are typically pneumatic or analog I/P and are used when a valve requires throttling action. They require position feedback from the valve stem or shaft and deliver pneumatic pressure to the actuator to open and close the valve.
Legacy processing units may use pneumatic pressure signaling as the control set point to the control valves. In a common pneumatic positioner design, a pneumatic input signal is received from a control device and modulates the supply pressure to the control valve actuator, providing an accurate valve stem or shaft position that is proportional to the pneumatic input signal.