Valve positioner

A position controller (servomechanism) that is mechanically

connected to a moving part of a final control element or its actuator and that automatically adjusts its output to the actuator to maintain a desired position in proportion to the input signal Pneumatically operated valves depend on a positioner to take an input signal from a process controller and convert it to valve travel.

– The valve positioner is a controller which can synchronize the

command signal and its corresponding valve step position.

– By use of valve positioner, hysteresis can be overcome

follow

http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf