What is SCADA? (Supervisory Control and Data Acquisition)

In this article, you will learn what SCADA is and how it works in a very easy-to-follow format.
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What is SCADA? The SCADA acronym stands for Supervisory Control and Data Acquisition. When considering this term, you can conjure varying images and you should.

A SCADA system is a collection of both software and hardware components that allow supervision and control of plants, both locally and remotely.

The SCADA also examines, collects, and processes data in real time.

Human Machine Interface (HMI) software facilitates interaction with field devices such as pumps, valves, motors, sensors, etc.

Also within the SCADA software is the ability to log data for historical purposes.

The structural design of a standard SCADA system starts with Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs).

As you know, RTUs and PLCs are microprocessors that communicate and interact with field devices such as valves, pumps, and HMIs.

That communication data is routed from the processors to the SCADA computers, where the software interprets and displays the data allowing for operators to analyze and react to system events.

Before SCADA, plant personnel had to monitor and control industrial processes via selector switches, push buttons, and dials for analog signals.

This meant that plants had to maintain personnel on site, during production, in order to control the processes.

As manufacturing grew and sites became more remote in nature, relays and timers were used to assist in the supervision and control of processes. With these devices employed, fewer plant personnel were required to be on site in order to oversee and control operations.

While relays and timers did provide some level of automation, the panels required for these devices took up valuable real estate, troubleshooting was a nightmare, and reconfiguring was difficult at best.

These issues, in conjunction with the need to grow even larger industrial plants, helped to facilitate the birth of automation.

SCADA Historical Review

– The 1950s

As you may know from the previous articles, controlling industrial plants via processors became a reality in the 1950s.
Gas and oil, utilities, and manufacturing were major users of these new technologies and supervisory control.

– The 1960s

About a decade later, telemetry came on the scene to offer even more remote capabilities with automated communication and data transmission to remote monitoring locations.

– The 1970s

Another decade later the term SCADA was used to describe systems with PLCs and microprocessors that were being used for the monitoring and control of automated processes on an even greater scale than ever before. SCADA, back then, was anything but practical.

They were colossal machines, mainframes really, and since networking was not yet in the picture, they were stand-alone units.

– The 1990s

In the next couple of decades, the ’80s and 90s, with computer systems getting smaller, the advent of Local Area Networking (LAN), and HMI software, SCADA systems were able to connect to related systems.

Unfortunately, though, the communications were typically proprietary which meant that connections outside of the particular vendor of the SCADA system were not allowed.

This early SCADA was coined “distributed SCADA systems”.

– The 1990s and 2000s

Later in the ’90s and 2000s, SCADA began to implement open system architectures with communication protocols that were not vendor specific.

As you can imagine, this opened up SCADA’s ability to connect with varying vendors. This newer, more improved SCADA was then called a networked SCADA system.

Newer and improved SCADA, unfortunately, didn’t last long.

With computer technology growing rapidly, IT development quickly gathered steam.
The default database for IT became Structured Query Language (SQL) databases.

SCADA developers didn’t implement these standard databases so SCADA became out of date rather quickly when other technologies so rapidly changed.


Current day SCADA systems have adapted to the changing technologies and have a great advantage over the older SCADA systems.

With the adoption of modern IT standards such as SQL and web-based applications, today’s SCADA allows for real-time plant information to be accessed from anywhere around the world.

Having this data at the operator’s fingertips facilitates improved plant operations allowing for responses to SCADA system queues based on field collected data and system analysis.

These operator interactions can be from a computer right on the plant floor to an office building in some other region in the world.

Advancing technologies have indeed made the world seem like a very small place, relatively speaking. And because the current SCADA system software has typically adopted the SQL database model, historical collection of data may be logged and used in trending applications to further improve plant processes as well as creating mandated record keeping for some of the industries out there.

Essentially, Supervisory Control and Data Acquisition (SCADA) is a collection of hardware and software components. This collection of components begins with real-time data collected from plant floor devices such as pumps, valves, and transmitters.

These components don’t have to be from a particular vendor, they just need to have a communication protocol that the processor can utilize.

Data collected from the field devices is then passed to the processors such as PLCs.
From the processor, the data is distributed to a system of networked devices.
These devices may be HMIs, end-user computers, and servers.

On the HMI and end-user computer, graphical representations of the operations exist for operator interactions such as running pumps and opening valves.
This data may also be analyzed and used to enhance plant production and troubleshoot problems.

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The RealPars Team

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