Remote terminal units (RTUs) and programmable logic controllers (PLCs) are both modern technological devices that impart connection to and control over mechanical objects and equipment from a distance.
While their functions are similar, when comparing an RTU vs. a PLC, we quickly discover they are distinct technologies intended for separate purposes:
- PLCs are built to be production tools used for automated manufacturing.
- RTUs are monitoring tools used to prevent and detect maintenance or security issues at remote locations.
While PLCs monitor the equipment they control, RTUs issue commands to equipment via control relays, however, these functions are secondary. While RTUs may be less suited to control assembly arms; PLCs are out of place monitoring fuel tank levels at a distant outpost.
So “RTU vs PLC” is an easy question to answer: each device is best for doing what it was built for. PLCs allow for nimble manufacturing and local area control. And, RTUs provide operational oversight, even over large geographical areas. Here’s more:
Comparing RTU vs. PLC
While similar, RTUs and PLCs differ in several important ways. These differences are the product of their intended use.
For example, remote terminal units can operate in low power modes for extended periods, reflecting their use in locations with little to no infrastructure.
PLCs, in contrast, typically require strong AC power connections to operate. PLCs, meant for local use, depend on high-speed, wired connections.
RTUs, meant for remote areas, communicate via wireless on high or low-speed connections.
These and several other differences demonstrate the intended uses of PLCs vs RTUs as shown below:
|Programming||Programmed by user||Pre-programmed|
|Power Needs||Moderate to High||Low to Ultralow|
|Connection Profile||High-speed wired||High or low-speed wireless|
|Durability||Moderate||High, Rugged for Various Temperatures and Conditions|
|Adaptability for SCADA||Primarily for local control||For small or large geographical distributed or SCADA control|
The ability to reprogram PLCs allows manufacturers to quickly reset their assembly lines for new products. RTUs with preprogrammed interfaces allow easy installation and continued long-term operation. While PLCs can stand up to manufacturing environments, rugged RTUs are better suited for harsh environmental conditions and remote facility operations.
RTUs are small enough for most remote equipment cabinets but tight assembly areas may require even smaller PLCs. Each attribute arises from the different intentions of the technology’s designers.
Applications for RTUs and PLCs
Often, the same company will use both RTUs and PLCs—for different applications. Deciding between an RTU vs. a PLC comes down to its purpose and environment. Applications that require diverse and capable motor control, found in manufacturing and robotics, work well with PLCs. However, monitoring applications, especially in large spread operations and remote areas, are best handled by RTUs. Industries which use RTUs include:
RTUs monitor environmental conditions and security at remote telecom sites. They ensure fast, informed maintenance responses by monitoring equipment conditions as well as the surrounding environment. RTUs can use control relays to perform simple motor functions, such as adjusting HVAC systems or turning on a generator if AC power is lost.
RTUs are effective railway technology devices used to monitor track conditions across thousands of miles of rail. In addition, RTUs will monitor train speed and position, and apply the brakes if it detects a dangerous situation. In addition, railyards and equipment site monitoring occurs via cameras and motion sensors connected to RTUs.
Remote sites and large equipment areas are common in utilities. RTUs can monitor substation equipment and environmental conditions. They’re also used to monitor water treatment facilities, keeping an eye on tank levels and valuable equipment.
Other Industries and Applications
RTUs and PLCs do have similar functions, and in some instances, their uses can overlap. For example, large industrial campuses, such as oil & gas refineries, must monitor and make adjustments to equipment across a wide area.
If AC power and a wired communications system are present, either an RTU or PLC will work. As PLCs are less costly, one would even be preferable. However, in an outdoor environment, the PLCs will degrade much faster than RTUs if not protected.
Choosing Between RTUs and PLCs
When evaluating the possibilities of an RTU vs. a PLC, you’ll realize that both monitor input from sensors and both can control objects through actuators. To summarize:
- PLCs are smaller, more programmable, stand-alone controllers to operate automatic processes in a single, local factory.
- RTUs, however, work for either local or wide geographical equipment monitoring, communicating from a distance, and engineered to monitor in even the most widespread and harshest conditions.
Choosing between them comes down to understanding the purpose of each, and the needs of your application. When your needs require large geographical, remote equipment monitoring, RTUs are your answer.
DPS Telecom has been a leading provider of RTUs to telecom, rail, utilities, and other industries. To learn more about protecting the valuable equipment at your remote sites with RTUs, reach out and get a quote today!
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