The level in a condensate collection tank is being controlled by an automatic level controller using proportional-only control.
Initially the tank level is stable, but then the flow into the tank increases and stabilizes at a higher flow rate.
As tank level increases, the controller positions a drain valve more open than necessary to stabilize the level.
As tank level decreases, the controller positions the drain valve more closed than necessary to stabilize the level.
This cycle is repeated continuously, never reaching a stable tank level or drain valve position.
The excessive valve positioning described above could be caused by the controllers gain being too __________; or by the controllers proportional band being too __________.
A. low; wide
B. low; narrow
C. high; wide
D. high; narrow
Show Answer
Answer: D
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