Refer to the drawing of a water storage tank with an automatic level control system (see figure below).
The level control system uses a reverse-acting level sensor and a direct-acting controller.
The flow rate of water entering the tank is constant, and within the capacity of the drain valve.
For the level control system to maintain a stable water level in the tank at a value up to 10 percent above or below the controller’s setpoint, the controller must have a __________ characteristic; and the drain valve must fail __________ on a loss of air pressure to its actuator.
A. proportional-only; closed
B. proportional-only; open
C proportional-integral; closed
D. proportional-integral; open
Show Answer
Answer: B
Share your understanding of this question with the correct explanation.