Question 248General Subjects - 1st Asst/Chief70% to pass
A 'Proportional Only' controlled automatic process loop is oscillating continually, above and below the set point. To stabilize this controller and loop using the 'gain' adjustment, what controller/loop response would you expect upon process changes vs. set point?
AI Explanation
The correct answer is C) By decreasing gain gradually, the process should stabilize in a 'quarter wave' response to system's upsets vs. the set point.
This is correct because in a proportional-only control system, decreasing the gain (or proportional term) gradually will help stabilize the oscillations and bring the process closer to the set point in a more controlled, quarter-wave response after a disturbance or upset. Decreasing the gain dampens the system's response, allowing it to settle without overshooting the set point.
The other options are incorrect because decreasing reset (option A) would not affect a proportional-only system, and increasing gain (option D) would actually increase the oscillations rather than stabilize them. Returning to a straight-line response (option B) is not the expected outcome of adjusting the gain in a proportional-only loop.
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