In a process controlled by a proportional-plus-integral controller, the measurement was at the set point and the output was 9 psi (60 kPa). The measurement then quickly decreased to a certain value below the set point and leveled out there. The output responded by changing to 8 psi (55 kPa). As time progresses, what would you expect from the output pressure?
A. Increase to 9 psi (60 kPa) to bring the measurement back to the set point
B. Remain at 8 psi (55 kPa) as long as the measurement stays where it is.
C. Decrease and continue to decrease to 3 psi (20 kPa).
D. Continue to decrease until the measurement reaches the set point, or if it does not return to the set point, decrease to 0 psi.
Answer:D
In a process controlled by a proportional-plus-integral controller, the measurement was at the set point and the output was 9 psi (60 kPa). The measurement then quickly decreased to a certain value below the set point and leveled out there. The output responded by changing to 8 psi (55 kPa). As time progresses, what would you expect from the output pressure?
A. Increase to 9 psi (60 kPa) to bring the measurement back to the set point B. Remain at 8 psi (55 kPa) as long as the measurement stays where it is. C. Decrease and continue to decrease to 3 psi (20 kPa). D. Continue to decrease until the measurement reaches the set point, or if it does not return to the set point, decrease to 0 psi.