Positioner

A control device attached to the control valve, which is designed to adjust and maintain the position of a control valve specified by the process control system against external influences (forces from the material flow, friction). In addition, the positioner is used to convert the reference variable W, i.e., either an analog standard signal (pneumatic 0.2–1.0 bar g or electrical 4–20 mA) or a digitally transmitted signal (fieldbus; e.g., Profibus or Foundation Fieldbus – FF) into a control variable Y (pressure & volume flow) suitable for the selected actuator using the available auxiliary energy (supply air pressure). In terms of control technology, the positioner represents a slave controller (cascade control) to the actual process controller.