Which of the following best describes the primary function of a controller in a closed-loop system?

• To amplify the input signal from the sensor

• To generate an output signal that directly drives the actuator without feedback

• To compare the process variable with the setpoint and generate a corrective control signal

• To record system data for later analysis

A system exhibits a persistent steady-state error (offset) despite a fast initial response. Which basic controller action, if added or increased, would most effectively eliminate this error?

• Proportional (P) action

• On-Off action

• Derivative (D) action

• Integral (I) action

The Derivative (D) term in a PID controller is particularly useful for

• Eliminating steady-state errors

• Anticipating future errors and reducing overshoot

• Providing slow and smooth control adjustments

• Responding to constant, sustained disturbances

What is a common disadvantage of using a Proportional (P) controller alone in many industrial applications?

• It often results in persistent steady-state error

• It introduces significant noise into the system

• It makes the system too slow to respond

• It cannot react to any changes in the process variable

If a control system displays severe oscillations and instability when responding to a setpoint change, which PID gain is most likely set too high?

• Ki​ (Integral gain)

• Kp​ (Proportional gain)

• Kd​ (Derivative gain)

• The sampling rate

The phenomenon where the integral term in a PI or PID controller accumulates a large value when the actuator reaches its saturation limit is known as

• Damping effect

• Integral kick

• Integral windup

• Proportional offset

Which of the following industries does not typically utilize PID controllers extensively for process automation?

• Food and Beverage processing

• Chemical and Petrochemical plants

• Power Generation facilities

• Traditional handicraft workshops (e.g., pottery without automated kilns)

A PD controller (Proportional-Derivative) is effective in improving transient response and reducing oscillations, but its main limitation is that it

• Is highly complex to implement

• Cannot eliminate steady-state error

• Is not suitable for fast-acting systems

• Overreacts to very slow changes

Consider a temperature control system. If the measured temperature is 180°C and the desired setpoint is 200°C, what is the value of the error signal (e(t))?

• -20°C

• 180°C

• 20°C

• 380°C

In a PID controller, the term that provides an "anticipatory" effect by reacting to the rate of change of the error is the

• Proportional term

• Integral term

• Derivative term

• Bias term