What is the process variable (PV) in a control loop?

Multiple Choice Questions Automation MCQ
1

Question:

What is the process variable (PV) in a control loop?

Options:

A) Measured value
B) Controller gain
C) Desired value
D) Output limit

View Answer

:white_check_mark: Correct Answer: A) Measured value

:magnifying_glass_tilted_right: Detailed Explanation

The Process Variable (PV) is the actual measured value of the parameter being controlled.

Examples:

  • Temperature in a furnace
  • Pressure in a pipeline
  • Flow rate in a line
  • Level in a tank

The PV is:

  1. Measured by a sensor
  2. Converted by a transmitter
  3. Sent to the controller

The controller then compares PV with the setpoint (SP):

Error = SP - PV

:cross_mark: Why Other Options Are Incorrect

B) Controller gain
Gain (Kp) is a tuning parameter, not a process measurement.

C) Desired value
That is the Setpoint (SP), not PV.

D) Output limit
Output limit refers to actuator constraints (0–100%), not the measured process.

:fire: Quick Memory

PV = Process Variable (Present Value)
SP = Set Point