Transmitters and Controllers — MCQs – EE

1. A transmitter in a control system is used to:
(A) Convert the output signal into mechanical energy
(B) Convert the sensor signal into a standardized form
(C) Control the final control element directly
(D) Generate process disturbances

2. The standard electrical output signal from most industrial transmitters is:
(A) 0–5 V
(B) 4–20 mA
(C) 0–10 V
(D) 1–10 mA

3. The main advantage of using a 4–20 mA signal instead of 0–20 mA is:
(A) Higher voltage drop
(B) Better calibration accuracy
(C) Easier fault detection (live zero at 4 mA)
(D) Increased signal bandwidth

4. A smart transmitter is characterized by:
(A) Pneumatic signal transmission
(B) Mechanical calibration
(C) Digital communication and self-diagnostics
(D) Manual signal control

5. A two-wire transmitter receives power:
(A) From a separate supply line
(B) Through the signal line itself
(C) From the sensor
(D) From the final control element

6. A transducer converts:
(A) One form of energy into another
(B) Mechanical motion into control action
(C) Temperature into pressure
(D) Voltage into current

7. The main function of a controller is to:
(A) Measure the process variable
(B) Compare measured value with the set point and take corrective action
(C) Actuate the final control element
(D) Eliminate disturbances

8. The set point in a control system is:
(A) The measured process variable
(B) The desired value of the controlled variable
(C) The error signal
(D) The output of the controller

9. A pneumatic transmitter transmits signals in the range:
(A) 4–20 mA
(B) 0–5 V
(C) 3–15 psi
(D) 1–10 V

10. The controller output is sent to:
(A) The measuring element
(B) The final control element
(C) The set point generator
(D) The transmitter

11. The P-controller output depends on:
(A) Rate of change of error
(B) Accumulated error
(C) Instantaneous error
(D) Square of error

12. The I-controller eliminates:
(A) Transient overshoot
(B) Steady-state error
(C) Frequency distortion
(D) Process gain

13. The D-controller improves:
(A) Steady-state accuracy
(B) Transient response and stability
(C) Process delay
(D) Control valve actuation

14. A PID controller combines the effects of:
(A) Proportional, Integral, and Derivative control
(B) Only proportional control
(C) Derivative and feedback only
(D) Integral control only

15. The Ziegler–Nichols method is used for:
(A) System stability analysis
(B) PID controller tuning
(C) Flow measurement
(D) Sensor calibration

16. A manual controller is operated:
(A) Automatically
(B) By the operator
(C) By feedback only
(D) Through the transmitter signal

17. The digital controller performs control action using:
(A) Continuous analog signals
(B) Discrete time signals processed by microprocessors
(C) Pneumatic pressure
(D) Mechanical linkages

18. The final control element in a process control system is usually a:
(A) Transmitter
(B) Control valve or actuator
(C) Sensor
(D) Indicator

19. The on–off controller operates:
(A) In continuous mode
(B) Between two discrete output levels
(C) With derivative action only
(D) With proportional action only

20. The proportional band in a controller represents:
(A) The range of error over which the controller output changes proportionally
(B) The steady-state gain
(C) The system bandwidth
(D) The sampling rate

21. A reset term in a controller refers to:
(A) Integral action
(B) Derivative action
(C) Proportional action
(D) Manual tuning

22. The rate action in a controller refers to:
(A) Integral action
(B) Derivative action
(C) Proportional action
(D) Manual adjustment

23. A cascade control system involves:
(A) Two or more controllers connected in series
(B) Only one feedback loop
(C) A single open-loop path
(D) Manual control

24. The ratio controller maintains:
(A) Constant ratio between two process variables
(B) Constant level
(C) Constant pressure
(D) Constant temperature

25. The feedforward controller acts:
(A) After the disturbance affects the process
(B) Before the disturbance affects the process
(C) Only in steady state
(D) Without sensing disturbances

26. A feedback controller acts:
(A) On predicted changes
(B) On measured changes after they occur
(C) Only on the set point
(D) On the transmitter input

27. In a two-wire transmitter, the loop power supply typically provides:
(A) 24 V DC
(B) 230 V AC
(C) 110 V AC
(D) 12 V DC

28. The zero adjustment of a transmitter is used to:
(A) Set output for minimum input signal
(B) Increase span
(C) Amplify the signal
(D) Reduce noise

29. The span adjustment of a transmitter is used to:
(A) Set output for maximum input signal
(B) Adjust feedback delay
(C) Tune proportional gain
(D) Set steady-state error

30. The HART protocol used with smart transmitters allows:
(A) Digital communication superimposed on 4–20 mA signal
(B) Only analog signal transmission
(C) Wireless data transfer only
(D) Pneumatic signal transfer

31. The controller gain determines:
(A) Speed and magnitude of corrective action
(B) Sensor accuracy
(C) Process delay
(D) Control valve size

32. The reset time in a controller represents:
(A) Time taken to eliminate steady-state error
(B) Sensor response delay
(C) Process delay
(D) Derivative action duration

33. The dead band in a controller is:
(A) Range of input where no output change occurs
(B) Proportional range
(C) Gain range
(D) Sampling delay

34. The controller tuning process adjusts:
(A) P, I, and D parameters for desired response
(B) Sensor calibration
(C) Power supply voltage
(D) Final control element feedback

35. The distributed control system (DCS) is:
(A) A centralized control system
(B) A system where control functions are distributed among multiple processors
(C) A pneumatic control system
(D) A manual control system