Red Seal Instrumentation and Control Technician Practice Exam

What is a characteristic of a proportional control in a PID controller?

1. It changes the control output based on the overall error

2. It only reacts to the accumulated error over time

3. It adjusts control output directly proportional to the setpoint error

4. It requires no feedback

The correct answer is: It adjusts control output directly proportional to the setpoint error

A characteristic of proportional control in a PID (Proportional-Integral-Derivative) controller is that it adjusts the control output directly proportional to the setpoint error. This means that if the difference between the desired setpoint and the measured process variable (the error) increases, the control output will also increase proportionally. This relationship allows the system to respond quickly to changes, maintaining the process at the desired level by providing more corrective action as the error grows. Proportional control is crucial for achieving a stable response without excessive oscillation. When the proportional gain is set appropriately, the system reacts to deviations from the setpoint in a manner that brings the process variable back toward the desired level. In contrast, the other choices refer to different aspects of PID control. One choice relates to overall error rather than the immediate error, another focuses on accumulated error over time (which is more a characteristic of integral control), and the last option suggests a lack of feedback, which is not applicable to a proportional control mechanism that inherently requires comparison of the setpoint and the process variable to calculate the control action.