The level in a water collection tank is being controlled by an automatic level controller that positions a tank drain valve.
Tank level is initially stable at the controller setpoint.
Then, flow rate into the tank increases, slowly at first, and then faster until a stable flow rate is attained.
When tank level increases, the controller begins to open the tank drain valve farther.
The level controller output signal increases both as the tank level increases and as the rate of the tank level change quickens.
After a few minutes, a new stable tank level above the original level is established, with the drain flow rate equal to the supply flow rate.
The controller in this system uses __________ control.
A. proportional only
B. proportional plus integral
C. proportional plus derivative
D. proportional plus integral plus derivative
Show Answer
Answer: C
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