What is RTU?

An RTU is a microprocessor-based device that monitors and controls field devices, connecting to plant control or SCADA systems. While some definitions suggest RTUs are more powerful than PLCs, both offer similar input/output capabilities.

PLCs generally have a lower price point than RTUs. However, RTUs are considered more rugged systems, which might offset higher initial costs in the long run. In terms of process control, both are on equal footing, offering various I/O and communication modules.

RTUs offer advantages in environmental tolerances, backup power options, and autonomy. They can withstand extreme temperatures and are often used in remote locations, communicating via radio, microwave, or satellite. Some RTUs also include backup batteries and charging circuits, like solar power, allowing operation during power outages, a feature often requiring a UPS for PLCs.

A potential programming advantage for RTUs is their ability to sometimes be programmed via a simple web interface or setup software. Some RTUs also have pre-programmed modules. However, this can also be a disadvantage as some RTUs require programming languages like Basic, Visual Basic, or C#, similar to PLCs which use ladder logic or structured text.

A significant advantage of RTUs is their environmental resilience. They are commonly used in harsh, remote environments such as mountaintops or offshore oil rigs, where reliable communication via radio, microwave, or satellite is essential and effectively managed by RTUs.

Many of the traditional advantages of RTUs can now be mitigated by newer PAC (Programmable Automation Controller) systems, which combine features of both. While environmental tolerance remains a strong suit for RTUs, modern technologies are continually leveling the playing field between RTUs and PLCs.