Difference Between PLC and RTU

PLCs and RTUs are both electrical devices with functionality that overlap. RTCs can be purchased with PLC-like characteristics, and PLCs can be purchased with RTC-like features.

Since the industry made the functional language operating RTUs and PLCs mainstream, many companies market proprietary replacements and other related environments to execute these programs.

Despite the fact that programmable logic controllers (PLCs) have become the industry standard, remote terminal devices are nevertheless used in a variety of applications (RTUs). Choosing which is best for your needs is a debate that is still ongoing.

PLC vs RTU

The main difference between PLC and RTU is that PLC is an abbreviation for the programable logic controller, and it is suitable for local control like amusements rides whereas RTU is an abbreviation for remote terminal units and is suitable for wider geographical telemetry. PLCs tend to have a lower price point than RTUs.

PLC vs RTU

The term “PLC” stands for “programmable logic controller.” They are usually utilized to automate electromechanical processes such as factory assembly lines, light fixtures, amusement rides, and so on.

They are designed specifically for output configurations with a large number of inputs. They can work at a variety of temperatures and are resistant to electrical noise, vibration, and impact.

RTU is a microprocessor-based device. It is primarily used to monitor and control field devices prior to connecting to plant control or SCADA. It can also be used to transform protocols.

RTUs must always be in contact with SCADA at the base station. The RTU provides a quick and adaptable answer to most control requirements.

Comparison Table Between PLC and RTU

Parameters of ComparisonPLCRTU
Full-FormProgrammable Logic ControllerRemote Terminal Units
Suitable ForLocal controlWider geographical telemetry
CostCheaperMore expensive
Tools UsedIEC 61131-3Alternate proprietary tools
ProcessingLocal processingLittle to no processing

What is PLC?

PLCs (programmable logic controllers) are electrical devices that control a process. The CPU, input and output devices, power supply, connectivity, and redundancy components comprise it.

PLCs are preprogrammed and deployed based on their application.

A PLC accepts field input, processes it according to programming, and then transmits commands to field equipment. It can also accept commands from plant operators and send them to field equipment via SCADA.

The features of PLCs vary from manufacturer to manufacturer, but the underlying design remains the same.

PLCs can function as stand-alone devices, but they are difficult to set up. They are unsuitable for use as a master controller in a control system.

If your system requires a large number of I/O to be monitored or controlled, a PLC is not the ideal option. They should not be used as protocol converters or to control other Intelligent Electronic Devices (IEDs).

PLCs provide a variety of functions such as process control, relay control, motion control, networking, and so on. They have begun to match desktop computers in terms of data storage, processing, communication, and handling.

PLCs are available in a variety of sizes, each with its own set of I/O and program capabilities. Their abilities differ widely, making broad generalizations problematic.

The PLC comes with its own native interface cards for the PLC manufacturer’s native protocol, but it relies on third-party interface cards for other Fieldbus protocols.

As a result, the engineering software configures the communication interface card for the native protocol automatically.

However, for other Fieldbus protocols, the interface card must be configured separately in order to map the variables before they can be utilized in the control strategy, graphics, and so on.

What is RTU?

RTU is an abbreviation for remote terminal units. It’s used to link field equipment to SCADA.

RTUs are generally used at distant stations to control equipment that is located a great distance away from the control station (for example, the opening and closing of motorized valves in oil pipelines).

RTUs can be programmed in the same way that PLCs can. RTUs can support multiple communication protocols at the same time.

It accepts just a restricted number of input and output devices. The primary role of RTUs is to collect telemetry data and control objects/equipment located in remote places.

RTUs (Remote Terminal Units) are intelligent enough to control a process or many processes without the intervention of a more intelligent controller or master.

It can function as both a slave and a master in a vertically deployed control system. It can also be used as a protocol or to control IEDs.

The term RTU is an abbreviation for “Remote Terminal Units.” They are also referred to as “Remote Telemetry Units.” An RTU’s principal duty is to connect the SCADA to the physical objects present.

The RTU does not support control loops or control algorithms.

Because of cheaper technology, the functionality of RTUs and PLCs began to converge, and the industry standardized the language for RTU-run programs. IEC 61131-3 has now become a standard.

Main Differences Between PLC and RTU

  1. PLC is short for programmable logic controller and RTU is short for remote terminal units.
  2. PLC are suitable for local control like amusement rides, assembly lines, etc. whereas RTUs are suitable for wider geographical telemetry since they use wireless communication.
  3. PLC is cheaper in comparison to RTUs.
  4. PLC used IEC 61131-3 whereas RTU usually uses other alternative proprietary tools.
  5. PLC requires local processing. On the other hand, RTUs require little to no processing.

Conclusion

So, the key difference between a PLC and an RTU in an application is that a PLC may work for you if you need a stand-alone device with electricity. However, some programming training must be prepared. PLCs can be challenging to set up.

A Remote Terminal Unit is required if you require an intelligent unit to control various processes without the intervention of a controller or master (RTU).

An RTU differs from a PLC in that it employs wireless communication and is better suited to broader geographical telemetry, whereas PLCs are better suited to local controls, such as production lines or factories.

The system is more based on physical media in plants and production lines. PLCs are more likely to employ IEC 61131-3, but RTUs are more likely to use proprietary tools.

References

  1. https://ieeexplore.ieee.org/abstract/document/6057539/
  2. https://ieeexplore.ieee.org/abstract/document/8394156/
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