One of the essential industrial automation systems for major industries, like water, electricity and oil and gas, is the SCADA system. Without this system, many industries will struggle to manage their operations, gather long-term viable data and help improve workplace productivity.

But, back to the beginning: what is a SCADA system? A SCADA (Supervisory Control and Data Acquisition) system is a central station that acts as a hub point to gather data, manage operations, communicate with workers, employ safe standards, and any other objective required by the business.

Key to the success of a SCADA system is the decision whether to choose between its terminal units. There are two vastly important, and different terminal units, that connect to the SCADA system: RTU (“Remote Terminal Units”) or PLC (“Programmable Logic Controller”).  

These two terminal units are essential for providing the central station with real-time and a breakdown of what is occurring around the facility. The central station oversees the overall performance of the RTUs and PLCs; giving operators the chance to make changes to the settings to ensure they are delivering the expected results all within a closed-loop feedback system.

While both devices are similar in their approach, there are differences with respect to their design use, capacity sizes and installation requirements. What are these differences? Does it matter? What is best for your system? This breakdown gives you the clear answers that you need.

The Differences Between RTU & PLC

DesignUse

An RTU is an electronic device that is controlled by a microprocessor. Its primary function is to interface with SCADA systems and provide the operator with the supervisory system messaging all units throughout the facility. All the information is transmitted to the network through telemetry data. RTUs are widely used for wider geographical telemetry, as the reach is more useful in these situations.

A PLC is a digital computer that is mainly used for automating electromechanical processes. You will most likely see PLCs at assembly lines, light fixtures and automated operating systems. They also offer electrical noise immunity, vibration and impact resistance and can withstand varied temperature ranges. You won't see them in wider geographical, unlike RTUs.

Capacity Of The Terminal Units

An RTU requires a more substantial capacity for its sensors, with more than 30 inputs, several outputs and a lot of communication interfaces. A PLC, on the other hand, is a small system, so, therefore, requires less capacity. A couple of digital/analog inputs, a similar number of open-collector/relay outputs and sometimes a single interface is all that is needed. So if you install an RTU, expect a vast network connection.

The Installation Requirements

PLC units sometimes require additional programming to perform its monitoring role, depending on what it is being used for, and how it plans on interfacing with the central station. RTUs, on the other hand, are pre-set for deployment into any SCADA system. The design is composed of an embedded configuration application that requires nothing more than a standard browser connection for setup.

What Works For Your SCADA System?

Deciding on which unit to select for your SCADA system depends on the operations of your enterprise and your marketing goals. If you are operating a vastly massive and challenging operation, an RTU will be beneficial for you. These systems are more robust and better suited to the high demands of a more extensive system.

PLCs are much better for simpler electromechanical processes - as we mentioned, assembly lines. They will be able to provide precise data and help you keep your systems under control. If your operations are not complex, then you should select a PLC.

Find The Right Unit For Your SCADA System

Your industrial automation is vital for the running of your operations. So you can see why it is essential to determine which unit - RTU or PLC - will work for your system. Doing so can make a massive difference to the overall operation and maintenance of your workplace. With your SCADA system, you want something that is going to be reliable, functional and can be adjusted to your operation. Quality is key here, so make sure that you look around for the best unit possible. Be sure you know what you are purchasing and that the system covers all of your needs.