Which one of the following describes the operation of a typical pneumatic valve positioner?
A. Compares the valve controller demand signal with actual valve position and sends an error signal to the valve controller for adjustment of the demand signal.
B. Compares the valve controller automatic and manual setpoints and sends an error signal to the valve controller to ensure the manual demand signal is tracking the automatic demand signal.
C. Receives a valve position error signal from the valve controller and positions the valve as necessary to null the valve position error signal.
D. Receives a demand signal from the valve controller and supplies the appropriate air pressure to the valve actuator to move the valve to the demanded position.
Show Answer
Answer: D
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