In a control loop, error is defined as the difference between which two parameters?

Multiple Choice Questions Instrumentation MCQ
1

In a control loop, error is defined as the difference between which two parameters during real-time operation of a process?

a. PV and output
b. SP and PV
c. SP and MV
d. PV and bias

View Answer:

:white_check_mark: Correct Answer: SP and PV

:brain: Concept Explained (Simple & Practical)

In any control loop, error is the key parameter that drives the controller.

:backhand_index_pointing_right: Error = Setpoint (SP) – Process Variable (PV)

e=SP−PV

:magnifying_glass_tilted_left: What Each Term Means

  • SP (Setpoint): Desired value
    :backhand_index_pointing_right: Example: Temperature should be 100°C
  • PV (Process Variable): Actual measured value
    :backhand_index_pointing_right: Example: Current temperature is 92°C

:gear: How Error Works in Real-Time

  • If SP = PV → Error = 0
    :check_mark: System is stable
  • If SP > PV → Error is positive
    :check_mark: Controller increases output
  • If SP < PV → Error is negative
    :check_mark: Controller reduces output

:cross_mark: Why Other Options Are Wrong

:cross_mark: PV and Output

  • Output is controller action, not part of error calculation

:cross_mark: SP and MV

  • MV (Manipulated Variable) is controller output

:cross_mark: PV and Bias

  • Bias is an internal controller parameter

:bullseye: Final Understanding

:backhand_index_pointing_right: Error is always the difference between what you WANT (SP) and what you HAVE (PV)

This error is what the controller uses to adjust the process and bring it to the desired condition.