A valve positioner relies on comparing the valve stem position with the actuator's ______?

A valve positioner relies on comparing the valve stem position with the actuator's ______?

• A. Input Signal
• B. Output Signal
• C. Feedback Pressure
• D. Ambient Temperature

Answer: (A)

The main idea is that a valve positioner operates as a closed-loop device to make the valve reach the exact position commanded by the control system. It uses the control signal from the process controller as the reference (the input signal) and compares it with the actual valve stem position. When there’s any difference, the positioner adjusts the air pressure going to the actuator to move the stem until the actual position matches the commanded position. Ambient temperature or the actuator’s own output pressure aren’t the reference for this comparison—the reference is the input signal from the controller, which is why the correct choice is the input signal.

The main idea is that a valve positioner operates as a closed-loop device to make the valve reach the exact position commanded by the control system. It uses the control signal from the process controller as the reference (the input signal) and compares it with the actual valve stem position. When there’s any difference, the positioner adjusts the air pressure going to the actuator to move the stem until the actual position matches the commanded position. Ambient temperature or the actuator’s own output pressure aren’t the reference for this comparison—the reference is the input signal from the controller, which is why the correct choice is the input signal.