In direct-acting control, output increases when?

Multiple Choice Questions Automation MCQ
1

Question:

In direct-acting control, output increases when?

Options:

A) PV rises
B) PV falls
C) Error zero
D) SP drops

View Answer

:white_check_mark: Correct Answer: A) PV rises

:magnifying_glass_tilted_right: Detailed Explanation

In a direct-acting controller, the controller output increases when the process variable (PV) increases.

Using the standard error formula:

Error = SP - PV

For direct action:

  • If PV rises
  • Controller output also rises

This type of action is used when increasing output must reduce the process variable (for example, cooling applications).

:repeat_button: Example

Cooling control loop:

  • Temperature (PV) rises
  • Controller output increases
  • Cooling valve opens more
  • Temperature decreases

The controller output moves in the same direction as PV — hence direct acting.

:cross_mark: Why Other Options Are Incorrect

B) PV falls → In direct action, output decreases when PV falls.
C) Error zero → Output remains steady at equilibrium.
D) SP drops → Direct/direct action is defined by PV behavior, not SP change.

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