Simply put, positioners are devices that allow us to accurately adjust a valves position, whether open, closed, or somewhere in between. While mostly used with control valves, they can also be used in on/off service.
All positioners require two things for proper operation – input and feedback. The control signal that provides a set point is known as the input, while the feedback indicates the current valve position.
Modern day positioners are digital. For pneumatic and electric actuators, they convert a 4-20mA input control signals to a proportional output. Depending on the signal, the valve position can be incrementally adjusted.
Positioners are also important components in industrial fieldbus networks. Their ability to control a valve’s position in times of emergency, shutdowns, and partial stroke tests make them a critical valve accessory.