Refer to the drawing of a water storage tank with an automatic level control system (see figure below).
The level control system has the following characteristics:
• The level sensor is direct-acting.
• The controller is reverse-acting.
• The controller uses proportional control.
• The controller’s setpoint is 12 feet.
• The controller’s proportional band is 6 feet to 18 feet.
• The drain valve will fail open if the actuator loses air pressure.
When the tank water level is 15 feet, the controller’s output will be _____ percent; and the drain valve will be _____ percent open.
A. 25; 25
B. 25; 75
C. 75; 25
D. 75; 75
Show Answer
Answer: B
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