Top 120+ SCADA Interview Questions and Answers for Automation Engineers (Beginner to Expert)

Published on Jun28, 2024 | Category: answer
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SCADA (Supervisory Control and Data Acquisition) systems are vital in industrial automation for real-time monitoring, control, and data acquisition across various industries like manufacturing, energy, water treatment, oil & gas, and more. SCADA systems allow engineers and operators to visualize processes, issue commands, collect historical data, and respond to alarms remotely or locally, increasing efficiency and reducing downtime.
This page is designed for automation engineers, instrumentation professionals, and SCADA aspirants preparing for job interviews. It provides a carefully curated list of the top 100 SCADA interview questions and answers, ranging from fundamental concepts to advanced implementation techniques. Whether you're a beginner learning the basics or an experienced professional brushing up for a technical interview, these questions cover key areas such as SCADA architecture, HMI design, communication protocols (Modbus, OPC, DNP3), integration with PLCs, security concerns, redundancy, troubleshooting, and modern advancements like IIoT and Industry 4.0.
By reading this page, you will:

Whether you're attending a job interview or upgrading your technical knowledge, this comprehensive guide will enhance your understanding of SCADA systems and increase your chances of success in the industrial automation field.

1. What is SCADA?

SCADA stands for Supervisory Control and Data Acquisition. It is a control system used in industrial automation to monitor and control processes remotely. SCADA systems collect data from sensors, devices, and PLCs, and present it in real-time to operators for supervision and decision-making.

2. What is the Role of SCADA?

The main role of SCADA is to monitor, control, and record data from industrial processes. It allows operators to supervise remote operations, detect faults quickly, trigger alarms, and ensure efficient and safe system operation from a central location.

3. How to Make a Secure SCADA System?

To secure a SCADA system, follow best practices:

4. Name of Any SCADA System

Popular SCADA systems include:

5. Tools of SCADA System

SCADA tools include:

6. Basic Parts of SCADA System

The main components of a SCADA system are:

7. What is Tag in SCADA System?

A tag is a variable or data point used in SCADA software to represent a sensor value, switch status, or calculated parameter. For example, a tag may represent the temperature of a tank or the on/off status of a motor.

8. How to Connect SCADA to PLC?

To connect SCADA to a PLC:

9. How to Connect SCADA to DCS System?

SCADA can be connected to a DCS system using standard protocols like OPC or Modbus TCP. The SCADA software reads process data from the DCS, allowing higher-level monitoring and centralized control.

10. What is Trend in SCADA?

A trend is a graphical representation of a variable over time. SCADA trends help operators visualize changes in temperature, pressure, flow, etc., for analysis and decision-making.

11. What is Alarm System in SCADA?

An alarm system notifies operators when a process variable goes outside its normal range. It highlights critical conditions, helps in quick decision-making, and prevents equipment failure or safety issues.

12. Why Alarm is Important in SCADA System?

Alarms are crucial for safety and operational continuity. They alert the operator of faults, abnormal situations, or emergencies, allowing quick action to minimize risks and downtime.

13. Why SCADA is Used?

SCADA is used to:

14. Difference Between SCADA and HMI

HMI (Human Machine Interface) is the part of SCADA that displays data and allows interaction. SCADA is a broader system that includes data collection, communication, control, and storage. HMI is just the user interface.

15. How to Design SCADA?

To design a SCADA system:

16. Types of Alarms in SCADA

Common SCADA alarm types:

17. How to Make User-Friendly SCADA System?

To make SCADA user-friendly:

18. Basic Requirements of SCADA System

SCADA system requirements include:

19. Different Parts of SCADA System

SCADA system parts include:

20. Can We Connect SCADA System to Multi-Brand PLC?

Yes, SCADA systems can communicate with PLCs from different manufacturers using standard protocols like Modbus, OPC, or Ethernet/IP. This makes SCADA flexible and vendor-independent.

21. What is SCADA Data Logging?

SCADA data logging is the process of storing process values like temperature, flow, pressure, etc., over time. This data is used for analysis, reporting, auditing, and troubleshooting.

22. What is Historian Role in SCADA System?

The historian in a SCADA system is a software or server that stores time-stamped data from various sensors and controllers. It helps in generating trends, reports, and identifying long-term performance or issues.

23. What Happens if Our SCADA System Suddenly Stops?

If a SCADA system stops unexpectedly, the operator may lose real-time visibility and control of the industrial process. Alarms, data logging, and commands will stop. However, most PLCs continue to run independently, ensuring basic process control. The SCADA system should be restored quickly to prevent safety or process issues.

24. How is SCADA Related to PLC?

SCADA and PLC work together in automation. PLCs handle field-level control by interacting with sensors and actuators, while SCADA monitors and supervises the entire process by collecting data from PLCs and displaying it through HMI screens. SCADA also sends commands back to PLCs when needed.

25. What is SCADA System Communication?

SCADA communication involves exchanging data between field devices (like PLCs or RTUs) and the SCADA server or HMI. This is done through wired or wireless protocols such as Modbus, OPC, DNP3, or Ethernet/IP.

26. Types of Communication in SCADA

Common communication types in SCADA include:

27. What are SCADA Protocols?

SCADA protocols define how data is exchanged between devices. Popular SCADA protocols include:

28. Can We Edit SCADA Screen When SCADA is Running?

Some SCADA systems support live editing (online mode), allowing changes to screens or tags while the system is running. However, it's generally recommended to make changes in offline/development mode and then deploy them to avoid runtime errors or disruptions.

29. Tools for SCADA

SCADA development and operation tools include:

30. Name SCADA Software

Examples of SCADA software include:

31. Name a SCADA System You Have Worked On

Example: "I have worked on Ignition SCADA by Inductive Automation. It offers a web-based HMI interface, SQL database integration, and modular development using Python scripting."

32. How to Start a SCADA System?

To start a SCADA system:

33. What is a Screen in SCADA?

A screen (or display) in SCADA is a graphical user interface that shows real-time process data, alarms, trends, and controls. Screens are created using graphic elements like tanks, valves, buttons, and meters.

34. What is a Picture in SCADA?

A picture refers to a complete HMI graphic or page within a SCADA system. It may contain multiple elements like indicators, buttons, and animations that represent a process area or equipment group.

35. Can We Make Multiple Screens in SCADA?

Yes, SCADA systems support multiple screens for different areas or process stages. Operators can switch between screens to monitor and control different sections of the plant efficiently.

36. What are Events and Actions in SCADA?

Events are specific conditions or triggers (e.g., a tag value exceeding a limit). Actions are tasks that the system performs in response (e.g., showing an alarm, sending an email, switching a screen). Together, they enable automation within the SCADA software.

37. Name Basic Visual Components of SCADA

Basic SCADA visual components include:

38. What is the Procedure to Make a SCADA System?

The SCADA development process includes:

39. Is HMI and SCADA the Same?

No, HMI (Human Machine Interface) is part of a SCADA system. HMI displays the graphical interface and user controls. SCADA includes HMI, communication systems, data logging, alarms, and reporting — providing full supervisory control over the process.

40. What is Data Server in SCADA?

A data server in SCADA is responsible for collecting data from field devices and distributing it to client HMIs or other services. It acts as a bridge between the control layer (PLCs/RTUs) and the operator interface.

41. Role of Database Software in SCADA System

Database software stores historical data, event logs, alarms, and configuration settings. It allows SCADA systems to:

42. Can We Store Tag Value in Database?

Yes, tag values can be stored in a database using a historian or SQL-based storage engine. This allows for long-term analysis, reporting, and system optimization.

43. What is DSN Configuration?

DSN (Data Source Name) configuration is used to connect SCADA software to an external database (e.g., SQL Server or MySQL). It defines the database name, driver, location, and credentials. SCADA uses DSN to log data or retrieve historical values for reporting.

44. What is Report in SCADA System?

A report in SCADA is a structured document that displays historical data, alarms, production counts, energy usage, or process summaries. Reports help in analysis, compliance, and performance monitoring. SCADA software can generate reports daily, weekly, or on demand using stored tag data.

45. What is PLC Tag and SCADA Tag? Are Both the Same?

A PLC tag is a variable in the PLC program representing real-world inputs or outputs. A SCADA tag is a representation of this PLC tag inside the SCADA software for monitoring and control. While they refer to the same process value, they exist in different environments (PLC and SCADA).

46. What is VBScript?

VBScript (Visual Basic Scripting Edition) is a lightweight programming language used in some SCADA systems (like WinCC) to automate tasks such as calculations, screen actions, or event handling in the HMI.

47. Types of Programming Languages Supported in SCADA

Common programming and scripting languages supported by SCADA platforms include:

48. What is Dependency of SCADA System?

SCADA depends on:

49. What If Communicating PLC Suddenly Stops?

If a PLC stops communicating, SCADA will lose real-time updates from that device. Alarms may trigger, and data on the screen may freeze. However, the rest of the system continues to operate unless other devices depend on that PLC's data.

50. Can We Take Full Backup of SCADA?

Yes, SCADA systems offer backup functionality. A full backup includes:

This ensures the system can be restored during failure or migration.

51. What are the Requirements of SCADA System?

To implement a SCADA system, you need:

52. Can SCADA Work on Different PCs?

Yes, SCADA systems support multi-PC architecture. The server handles core data processing, while clients (on different PCs) access screens and data over a network. This allows multiple users to monitor and control the system simultaneously.

53. What is a Remote SCADA Server?

A remote SCADA server is hosted off-site or in another part of the plant and accessed via network or VPN. It collects data from remote stations and makes it accessible to operators over secure connections, often used in water, oil, or power industries with distributed assets.

54. SCADA Data Types – Why Are They Important?

SCADA tags use various data types such as:

Correct data types ensure accurate data handling, proper display, and efficient storage.

55. What are the Features of SCADA?

Key SCADA features include:

56. What is RTU (Remote Terminal Unit)?

An RTU is a device used in SCADA to connect sensors and actuators to the central system, especially in remote locations. It collects analog/digital inputs and sends data to the SCADA system via communication protocols like Modbus or DNP3.

57. Basic Network Diagram of SCADA

A simple SCADA network includes:

This setup enables real-time data flow from field to operator.

58. What is Data Exchange?

Data exchange in SCADA refers to the transfer of data between devices (e.g., PLC to SCADA), between applications (e.g., SCADA to database), or between systems (e.g., SCADA to ERP). It's essential for coordinated control and reporting.

59. What is DDE (Dynamic Data Exchange)?

DDE is a legacy method of exchanging data between applications, like SCADA and Excel. Although outdated and replaced by OPC in most systems, some older SCADA platforms may still support DDE for simple data links.

60. Can We Connect SCADA with OPC?

Yes, most modern SCADA systems support OPC (OLE for Process Control). OPC allows communication between devices from different manufacturers by acting as a universal translator, improving compatibility and integration.

61. Role of OPC in SCADA

OPC simplifies integration by standardizing data exchange. It allows SCADA to:

62. Role of Database Software in SCADA

The database stores and organizes large volumes of process data, alarms, logs, and reports. It supports:

63. What is MSSQL?

Microsoft SQL Server (MSSQL) is a relational database used by many SCADA systems for storing historical data, alarms, and configuration settings. It allows complex queries and integrates easily with reporting tools and analytics dashboards.

64. Is MSSQL Used in SCADA?

Yes, many SCADA platforms (like Ignition, WinCC, and iFIX) use MSSQL for:

65. Name of Database Software Which We Can Connect with SCADA

SCADA systems can connect with:

66. Types of Trends in SCADA

SCADA systems support different types of trend displays:

67. What is User Role in SCADA?

User roles define what each user can do within the SCADA system. Roles include:

This helps in ensuring security and organized access control.

68. What is Security in SCADA?

Security in SCADA involves protecting the system from unauthorized access, cyber attacks, and tampering. It includes user authentication, network protection, secure coding practices, and data encryption to keep systems safe and reliable.

69. How to Prevent SCADA from Unauthorized Use?

To prevent unauthorized use:

70. How to Prevent SCADA from Unauthorized Editing of Screens?

To prevent screen editing:

71. What is User Management in SCADA?

User management allows SCADA administrators to create, modify, and delete users, assign roles, and manage passwords and permissions. It ensures that each user can only access authorized parts of the system.

72. If a Screen is Already Created, Can We Re-Edit?

Yes, most SCADA systems allow screen editing after creation using the development environment. You can modify graphics, add new controls, or change tag links. However, edits should be tested before deploying to runtime.

73. Use of Scripting in SCADA

Scripting is used to add custom logic to SCADA systems, such as:

Common scripting languages: VBScript, Python, JavaScript.

74. What is ActiveX Control in SCADA?

ActiveX controls are reusable software components used in some SCADA systems (like WinCC) to extend functionality. They can be used to display graphs, charts, or integrate third-party controls like Excel objects, enhancing screen interactivity.

75. What is IIoT?

IIoT stands for Industrial Internet of Things. It refers to the use of smart sensors, devices, and internet technologies to collect and exchange data in industrial settings for advanced monitoring, analytics, and automation.

76. Role of SCADA in the Internet of Things (IoT)

SCADA acts as a gateway in IIoT by:

77. How to Prevent SCADA from Cyber Attacks?

Cybersecurity measures include:

78. How Does SCADA Work?

SCADA works by:

79. How Does SCADA Handle Processes?

SCADA does not directly control processes — it supervises them. PLCs or RTUs perform control actions based on logic, while SCADA:

80. How Does SCADA Handle Data from PLC?

SCADA communicates with PLCs using protocols like Modbus or OPC to read tag values (inputs/outputs, counters, etc.). It maps these values into SCADA tags, displays them on screens, logs them, and responds to threshold conditions with alarms or scripts.

81. Can We Add Program in PLC Using SCADA?

No, SCADA cannot be used to upload or change PLC programs. PLC programming must be done using dedicated software (e.g., TIA Portal, RSLogix). SCADA can only monitor and send command values to PLCs.

82. Can SCADA Change PLC Tag Value?

Yes, SCADA can write to PLC tags (like setpoints, control commands) as long as:

83. How to Visualize a Process in SCADA?

You can visualize a process in SCADA by:

84. Can SCADA Handle Real-Time Data?

Yes, SCADA is designed for real-time monitoring. It continuously reads data from PLCs and updates the HMI screens instantly. Trends, alarms, and control commands work in real-time to ensure safe and efficient operation.

85. What Should You Do to Make SCADA Operate Better?

To optimize SCADA performance:

86. Which Type of Documentation is Required for SCADA Training Purposes?

Important training documents include:

These help in onboarding operators and engineers efficiently.

87. How to Documentize SCADA System?

Documenting a SCADA system involves recording the system architecture, tag configurations, screen layouts, alarms, scripts, user roles, and communication settings. This helps in training, troubleshooting, maintenance, and audits.

88. Basics of SCADA Documentation

Key elements of SCADA documentation include:

89. Can We Test SCADA Without Deployment in Real Process?

Yes, SCADA systems can be tested in simulation mode using:

This ensures screen logic and alarm functions work correctly before real deployment.

90. What is Mobile SCADA and Remote SCADA?

Mobile SCADA allows operators to monitor and control systems via smartphones or tablets using mobile apps or web interfaces. Remote SCADA enables access to SCADA systems from remote locations using secure internet connections, often via VPN, cloud, or web servers.

91. Basics of a User-Friendly SCADA System

To make SCADA user-friendly:

92. What is Wireless Communication?

Wireless communication is the transmission of data without cables, using RF, Wi-Fi, GSM, or Bluetooth. In SCADA, it connects remote PLCs, sensors, or RTUs to the main system over long distances.

93. Can We Connect PLC with Wireless?

Yes, PLCs can communicate wirelessly using:

Wireless communication is useful in distributed or mobile applications like water treatment, oil wells, and remote stations.

94. What is Windows Web Server in SCADA?

A Windows web server (like IIS) can host SCADA web applications that allow remote access via a browser. It serves web pages, scripts, and APIs for real-time monitoring of SCADA data over LAN or the internet.

95. What is the Role of IIS Server in SCADA?

IIS (Internet Information Services) is a Microsoft web server used in SCADA to:

96. How to Configure SCADA in IIS Server?

To host SCADA in IIS:

97. Can We Make Web Screen of SCADA?

Yes, modern SCADA platforms (like Ignition, WinCC OA, AVEVA Edge) support web-based HMIs. These screens run on HTML5 or JavaScript, and are accessible from any browser without special software.

98. What is a Firewall?

A firewall is a network security system that monitors and controls incoming and outgoing traffic. In SCADA, firewalls are used to protect systems from unauthorized access, malware, and cyber threats by filtering traffic based on rules.

99. How Firewall Works in SCADA?

In SCADA, a firewall:

100. What is Port in SCADA and How to Secure It?

A port is a logical endpoint for network communication (e.g., port 502 for Modbus TCP). To secure SCADA ports:

101. What is Port Forwarding in SCADA?

Port forwarding is used to expose a SCADA service running inside a private network to the internet. It redirects traffic from an external port on a router to a specific internal IP and port. It's useful for remote access but must be secured.

102. What is License in SCADA?

A SCADA license determines how many tags, screens, or users you can use. Licenses are issued per client, per server, or per feature (e.g., historian, alarm module). Licensing also controls runtime vs. development usage.

103. Can We Use SCADA Without License?

Most SCADA platforms offer trial or demo versions with limited functionality. Using SCADA without a valid license in production is illegal and can disable core features. Always use licensed versions for commercial and industrial applications.

104. What is Redundancy in SCADA System?

Redundancy means having backup systems (e.g., redundant servers, network paths, or PLCs) to ensure continuous SCADA operation even if one component fails. Redundancy increases system availability and reliability.

105. How to Troubleshoot SCADA?

Steps to troubleshoot SCADA:

106. What are Common SCADA Problems?

Common SCADA issues include:

These can often be resolved through diagnostics and proper configuration review.

107. What is Communication Error and How to Resolve It?

A communication error occurs when SCADA fails to exchange data with PLCs, RTUs, or servers. Causes include:

To resolve it:

108. What is Master Station in SCADA?

The master station is the central server in a SCADA system that collects data from field devices (PLCs/RTUs), processes it, stores it in databases, and presents it to operators through HMIs. It may also send control commands to field devices.

109. What is Station System in SCADA?

A station in SCADA refers to an operational node — such as:

Each plays a role in the overall SCADA architecture.

110. How SCADA Controls a Process?

SCADA supervises the process via PLCs or RTUs:

SCADA does not perform logic — that is done by PLCs.

111. Can SCADA Control Process Without PLC?

In limited cases, SCADA can control processes using direct IO cards or soft logic, but it is not recommended. For industrial control, PLCs or RTUs are essential as they handle real-time execution and fail-safe behavior.

112. How to Customize SCADA Screen?

To customize SCADA screens:

You can also create templates for reuse across multiple screens.

113. What is SCADA Life Cycle?

The SCADA system lifecycle includes:

Like any industrial system, it's important to plan for the entire lifecycle, including future scalability.

114. Steps to Make a SCADA System

115. How to Select SCADA for a System?

Consider these factors:

Popular options include Ignition, WinCC, iFIX, and AVEVA.

116. What are the Basic Requirements of a SCADA System?

117. How to Upgrade SCADA?

118. What is the Role of SCADA in Industry?

SCADA plays a vital role in industrial automation by:

Industries: Water, Power, Manufacturing, Oil & Gas, etc.

119. What Are the Three Types of SCADA?

120. What Are the Basics of SCADA?

SCADA basics include:

SCADA bridges field devices and operator control stations.

121. What Are the Three Main Components of SCADA?

Together, these enable data acquisition, monitoring, and control of industrial systems.

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