Which type of process control uses a mode where the output is directly proportional to the deviation from the set point?

Which type of process control uses a mode where the output is directly proportional to the deviation from the set point?

• A. Proportional control
• B. Floating proportional control
• C. Proportional plus reset control
• D. Proportional plus reset plus derivation control

Answer: (A)

Proportional control is defined by a controller output that is directly proportional to the current error, the deviation from the set point. In a control loop, the error is what you get when you subtract the measured variable from the desired set point, and the controller multiplies that error by a gain to produce the control signal. So as the deviation grows, the output grows in direct proportion, driving the process toward the set point. This exact description—output changing in direct proportion to the deviation from the set point—best matches proportional control. More complex schemes add integral or derivative actions that alter how the output responds over time or to the rate of change, so they don’t describe the simple one-to-one proportional relationship.

Proportional control is defined by a controller output that is directly proportional to the current error, the deviation from the set point. In a control loop, the error is what you get when you subtract the measured variable from the desired set point, and the controller multiplies that error by a gain to produce the control signal. So as the deviation grows, the output grows in direct proportion, driving the process toward the set point.

This exact description—output changing in direct proportion to the deviation from the set point—best matches proportional control. More complex schemes add integral or derivative actions that alter how the output responds over time or to the rate of change, so they don’t describe the simple one-to-one proportional relationship.