SCADA system interview questions

1. What is SCADA?

SCADA stands for Supervisory Control and Data Acquisition. It is an industrial control system that controls and monitor. The operator can control and monitor the process from the SCADA station.

2. What are the components of SCADA?

3. What is Data Acquisition?

Data acquisition refers to the method used to access and control the information or data of the equipment that is controlled and monitored. The data that is accessed is sent to a telemetry system ready to be transferred to the different sites. They can be analog and digital information collected by sensors, such as flowmeter, ammeter, etc.

4. What is the Power Supply provided to the RTU?

Remote Terminal Units (RTUs) are operated from 110V/240V + or - 10% and 50Hz or 12/24/48V + or - 10% DC Voltage.

5. Applications of SCADA.

  • Industrial automation

  • Power distribution

  • Building, Airport, HVAC, Energy consumption system.

  • Water management system etc…

6. What is HMI?

HMI is Human Machine Interface, usually linked with the SCADA database and software program. to provide trending, diagnostic data and information management for scheduled maintenance and logistic information on different machines and sensors in the field.

7. What is SCADA historian?

Historian is a service that collects data from different devices and stores them in the database. It stores data in the time series database and can retrieve it to study the performance of a system.

8. What is DDE?

DDE is Dynamic Data Exchange which is a communication protocol that allows the server to communicate with windows device. It could implement client-server communication. DDE is used to gather and distribute live data such as production measurement, instrument reading etc.,

9. What is RTU?

RTU, Remote Control Unit is an electronic device that is used in industrial control systems such as DCS and SCADA. It is a microprocessor-based device, works as a standalone data acquisition and control unit

10. What type of licensing patterns used in the SCADA software?

Dongle Key: It is a hardware lock which can be put on the communication port of the PC.

Software Lock: Here the software code is the license. Typically you can put the code while installation or transfer the code from Floppy to hard-disk.

11. What is CMS?

CMS is a Centralized monitoring system, which is the master unit of the SCADA system. It is responsible for collecting the information collected by the remote stations and generating the necessary actions for any detected event. The CMS can have a single computer configuration or can be networked to work stations to allow the exchange of information from the SCADA system.

12. Leading SCADA companies

  • Invensys Wonderware InTouch

  • Siemens WinCC (Earlier COROS)

  • Allen Bradley RS View (Earlier Control View)

  • Intellution iFix (Earlier Fix DMACS)

  • GE Fanuc Simplicity

13. What are the different types of communication configurations in SCADA?

There are two modes of communication available, namely, the polled system and the interrupt system.

  • In the Polled or Master/Slave system, the master is in total control of communications. The master makes a regular polling of data (i.e., sends and receives data) to each slave in sequence

  • The interrupt system is also referred to as Report by Exception (RBE) configured system. Here the slave monitors its inputs. When it detects a significant change or when it exceeds a limit, the slave initiates communication to the master and transfers data. The system is designed with error detection and recovery process to cope with collisions.

14. What ate the types of remote stations used for SCADA?


15. Difference between RTU and PLC

RTU is used where communication is difficult, while PLC is low cost and have advantages of good programmability.