Difference Between SCADA and PLC

Supervisory Control and Data Acquisition (SCADA) Systems include all the sensors, connections (gateways), PLCs, Human-machine interfaces, and servers involved in an automated process. Programmable Logic Controllers (PLCs) are an important part of hardware within the SCADA System.

Trying to make sense of SCADA and PLCs so you can work with an engineer and/or contractor on an automation process for your California business? Don’t worry! We’ll break down the differences between SCADA and PLCs.

This Access Industrial Automation blog post will explain the differences between SCADA and PLCs. We’ll also shed some light on why you may be confused after reading a few different explanations online.

If you would like a more general explanation of industrial automation, read this blog post about the Pros and Cons of Industrial Automation.

SCADA Systems vs. PLCs in Automation

Supervisory Control and Data Acquisition (SCADA) Systems and Programmable Logic Controllers (PLCs) are both important in automation.  SCADA Systems include all the hardware and software needed to control, monitor, and collect data. PLCs are hardware within that system.

We’ll look more closely into the differences between SCADA and PLCs so that you feel more confident in the differences and similarities. 

Alternate Definition of SCADA

Supervisory Control and Data Acquisition (SCADA) is sometimes defined as only software in the automated process. In this case, the difference between SCADA and PLCs is that one is hardware, and the other is software. However, there’s a greater consensus on referring to the entire system as SCADA.

For this blog post, we are going to use the definition with the greatest consensus among Google search engine results: Supervisory Control and Data Acquisition (SCADA) systems include all of the hardware and software in an automated process.

Key Differences in Function: SCADA vs. PLCs

Supervisory Control and Data Acquisition (SCADA) Systems have more functions than Programmable Logic Controllers (PLCs). That’s because SCADA has to collect data, monitor functions, and control the automated process. PLCs use the data to control some of the processes automatically.

Supervisory Control and Data Acquisition (SCADA) System Tasks

• Collect data from sensors
• Receive inputs from manual controls
• Monitor function and efficiency by analyzing data according to programming
• Send appropriate information to designated human-machine interfaces (HMI)
• Send information to on-site and/or remote servers
• Initiate alarms, notifications, and safety protocols

Programmable Logic Controller (PLC) Tasks

• Monitors inputs and outputs to detect errors
• Initiates emergency shutdown protocols when needed
• Maintains process function when conditions are safe and stable
• Perform these tasks within the scope of the whole SCADA System

It’s not a matter of SCADA or PLCs being better or more important than the other. Without PLCs, SCADA systems would not function. PLCs on their own do not perform all of the SCADA system’s tasks.

When SCADA Systems Were Developed

Supervisory Control and Data Acquisition Systems (SCADA) Systems have been around since the beginnings of industrial automation in the mid-20th century. Before SCADA and automated processes, industrial processes required human input to initiate and monitor every task in the process.

SCADA has changed over the decades as the components like sensors, computers, and human-machine interfaces have technologically advanced. The first SCADA systems before personal computers are unrecognizable from today’s that can be operated from a smartphone.

When PLCs Were Developed

Programmable Logic Controllers (PLCs) were developed in the 1960s as a solution to improve automated processes. PLCs were more sophisticated than the relays that were being replaced, using more advanced switching. PLCs have become even more advanced and capable since the early PLCs of the 1960s.

SCADA Sytems, PLCs, and Safety

Supervisory Control and Data Acquisition (SCADA) Systems and Programmable Logic Controllers (PLCs) share responsibility for industrial workplace safety. PLCs have the ability to initiate an automatic shutdown when unsafe conditions are detected. 

SCADA systems send notifications to human-machine interfaces (HMI) that also allow for safety. These early detection warnings have improved workplace safety and efficiency. 

As all of the components within the SCADA system become more sophisticated, from the sensors (like thermometers and pressure gauges) to the PLCs and HMIs, the ability to keep workers and equipment safe improves.

For example, early automation systems detected a fire and initiated warnings. Now, SCADA systems can use data to determine when there’s even a risk of fire and can begin the appropriate steps to protect people and equipment.

California Automation Services

Access Industrial Automation provides automation and PLC services in central California. You can get expert advice and help in fixing or improving your industrial automation. Contact Access Industrial Automation online or by calling (209)-577-1491 during regular business hours.

Frequently Asked Questions

How Are SCADA Systems and PLCs connected?

SCADA systems collect, analyze, and interpret data to control automated processes. Programmable Logic Controllers (PLCs) are a hardware component of this. The PLC receives input from sensors and is programmed to respond automatically and send information to the rest of the SCADA system. 

Can you have a SCADA system without PLCs?

Supervisory Control and Data Acquisition (SCADA) systems rely on Programmable Logic Controllers (PLCs) to perform all of the functions. SCADA needs various automation components. Note that PLCs are able to perform their tasks without SCADA software.

Should I learn about SCADA or PLCs?

SCADA and PLCs work together in an automated process. It’s not a matter of using or learning one or the other. From a learning standpoint, learning PLCs before SCADA may help you comprehend SCADA as a whole better.

Are Programmable Logic Controllers (PLCs) part of SCADA?

Programmable Logic Controllers (PLCs) are hardware components in the Supervisory Control and Data Acquisition (SCADA) System. Some define SCADA as all of the hardware and software, including PLCs. Others define SCADA as the software that uses inputs from hardware like PLCs to oversee the process.

Are SCADA and PLCs obsolete?

SCADA and PLCs are still in use in automated processes today. The SCADA and PLC technology is constantly improving, so updates to the hardware and software every 5-10 years are needed to stay as efficient and competitive as possible.