The primary function of a valve positioner is to:

A valve positioner is a critical component in process control systems, specifically in controlling the position of a valve in response to signals from a controller. Its primary function is to maintain the correct position of the valve in accordance with the desired setpoint provided by the control system. This capability ensures accurate control over the flow of the process medium by adjusting the valve's position based on real-time feedback.

When a control signal is sent to a valve, the positioner interprets this signal and adjusts the actuator position to match the desired valve position. By continuously monitoring and correcting the valve's physical position, the positioner ensures that the flow through the valve meets the process requirements precisely. This function is essential to achieve the desired process variables, such as pressure, temperature, or flow rate.

While aspects like automating valve opening, regulating flow rate, and preventing backflow are certainly related to valve operation and control, they are secondary functions that rely on the accurate positioning that the positioner provides. Therefore, maintaining the valve position is fundamental to the overall performance and efficiency of a control system.