SCADA and PLC Systems — MCQs – EE

1. The term SCADA stands for:
(A) Supervisory Control and Data Acquisition
(B) System Control and Direct Access
(C) Supervised Control and Distributed Automation
(D) Signal Control and Data Analysis

2. The main function of a SCADA system is to:
(A) Control and monitor industrial processes remotely
(B) Manufacture industrial components
(C) Manage office automation
(D) Record employee attendance

3. A PLC is primarily used for:
(A) Logic control and automation of industrial processes
(B) Data storage
(C) Power generation
(D) Office computing

4. The term PLC stands for:
(A) Process Logic Computer
(B) Programmable Logic Controller
(C) Process Line Control
(D) Programmed Load Circuit

5. The CPU of a PLC is responsible for:
(A) Executing control instructions
(B) Storing only user passwords
(C) Managing communication cables
(D) Providing AC supply

6. In a SCADA system, RTU stands for:
(A) Remote Terminal Unit
(B) Real-Time Utility
(C) Random Transfer Unit
(D) Remote Transfer Utility

7. The HMI (Human Machine Interface) in SCADA is used for:
(A) Allowing operators to interact with the system
(B) Measuring voltage levels
(C) Storing PLC programs
(D) Generating alarms

8. The I/O module in a PLC is used to:
(A) Interface field devices with the PLC
(B) Provide power to sensors
(C) Store ladder logic
(D) Control memory allocation

9. The ladder diagram is commonly used in:
(A) PLC programming
(B) Circuit design
(C) Network configuration
(D) Safety testing

10. The analog input module of a PLC handles signals like:
(A) Voltage and current
(B) Start/Stop push buttons
(C) Limit switches
(D) Relay outputs

11. The digital input to a PLC can be from:
(A) Push buttons and switches
(B) Thermocouples
(C) Potentiometers
(D) Analog sensors

12. In a PLC system, scan time refers to:
(A) The time taken to read inputs, execute logic, and update outputs
(B) The delay between two alarms
(C) The time taken to transmit data to SCADA
(D) The communication lag between devices

13. SCADA systems are mostly used in:
(A) Power plants, oil refineries, and water treatment plants
(B) Schools and colleges
(C) Hospitals only
(D) Banking sectors

14. A distributed control system (DCS) differs from SCADA mainly because it:
(A) Operates within a local plant area
(B) Controls global systems
(C) Has no data acquisition
(D) Cannot use PLCs

15. The communication protocol used in SCADA systems includes:
(A) Modbus, Profibus, and DNP3
(B) FTP and HTTP only
(C) SMTP and POP3
(D) USB and HDMI

16. The redundancy in SCADA systems is implemented to:
(A) Increase system reliability and reduce downtime
(B) Add more sensors
(C) Decrease system cost
(D) Limit data collection

17. The ladder logic programming language is based on:
(A) Electrical relay logic diagrams
(B) Mechanical circuit design
(C) Sequential function charts
(D) Binary counters

18. RTUs are used in SCADA systems for:
(A) Collecting field data and sending it to the central system
(B) Controlling local machines directly
(C) Generating electrical power
(D) Performing complex calculations

19. Sensors and actuators in a PLC system are connected to:
(A) Input and output modules
(B) CPU directly
(C) HMI
(D) SCADA display

20. The non-volatile memory in a PLC is used to:
(A) Store user programs permanently
(B) Execute real-time instructions
(C) Measure analog signals
(D) Record alarm history

21. PLC scan time mainly depends on:
(A) Number of inputs/outputs and program complexity
(B) Cable length
(C) Ambient temperature
(D) Operator skill

22. The watchdog timer in PLC is used to:
(A) Detect and reset the system in case of faults
(B) Control temperature
(C) Reduce program size
(D) Increase cycle speed

23. The historian in a SCADA system is responsible for:
(A) Storing and managing process data over time
(B) Controlling analog outputs
(C) Sending alarms
(D) Editing ladder programs

24. PLC programming languages are defined under the standard:
(A) IEC 61131-3
(B) ISO 9001
(C) IEEE 1588
(D) ANSI C

25. The advantages of using PLCs include:
(A) High reliability and flexibility in control
(B) High maintenance cost
(C) Limited programming options
(D) Complex hardware wiring

26. The operator interface in SCADA is called:
(A) Human Machine Interface (HMI)
(B) Terminal Box
(C) Operator Switch
(D) Field Display

27. SCADA alarms are used to:
(A) Alert operators about abnormal conditions
(B) Change set points automatically
(C) Record temperature changes only
(D) Stop system operation permanently

28. The communication link between PLC and SCADA can be:
(A) Ethernet, RS-232, or RS-485
(B) USB only
(C) Wireless only
(D) HDMI

29. The PLC output devices include:
(A) Motors, lamps, relays, and solenoid valves
(B) Sensors and switches
(C) RTUs
(D) Displays only

30. The main advantage of SCADA systems is:
(A) Centralized monitoring and control of remote processes
(B) Reduced data storage
(C) Manual operation of equipment
(D) Local-only access