Question

The variable which is manipulated to make the controlled variable remain at the set point value is known as

• A. Controlled variable
• B. Load variable
• C. Manipulated variable
• D. Complex variable

Hint:

Think of it this way: The Controlled variable is the "Goal," and the Manipulated variable is the "Tool" used to achieve that goal.

Answer 1

The Correct Option is C

1. Identifying System Variables:

• Controlled Variable (CV): This is the actual parameter we want to maintain at a specific value (the setpoint), such as the temperature of a room or the level of water in a tank.

• Manipulated Variable (MV): This is the parameter that the controller changes or "manipulates" to affect the controlled variable. For example, to control room temperature (CV), the controller adjusts the flow of fuel or electricity to a heater (MV).

2. The Control Logic: When the sensor detects a deviation (error) between the current controlled variable and the setpoint, the controller calculates a new output. This output physically alters the

manipulated variable to drive the error back to zero.

3. Distinction from Load Variables: A load variable (or disturbance) is an external factor that changes and pushes the controlled variable away from the setpoint (e.g., someone opening a window in a heated room). The manipulated variable is our tool to counter the effects of these load variables.