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PID Controllers VS RTUs for Remote Sites: Pros and Cons

Morgana Siggins
Morgana Siggins
Monitoring Specialist

If you are researching about remote monitoring and control, chances are that you came across the words "PID controller" and "RTU" a couple of times.

Especially if you need to deploy a brand new monitoring system for your network, and don't know yet which gear would fit better in your scenario, it's very important to know what each equipment type is and exactly what they can do so you can choose wisely.

Even though at DPS Telecom we specialize in offering custom monitoring devices, such as RTUs and master stations, we see ourselves as your partner in securing your network and we put your needs first. We don't want to leave you with a monitoring problem that's unsolved, even if it means that RTUs are not the best devices for you.

So, let's explore the main pros and cons with PID controllers and RTUs, as well as their main differences and the best practices to keep in mind when purchasing these devices.


What is a PID Controller?

A Proportional Integral Derivative - or simply PID - controller is a device used in industrial control applications to regulate Process Variables (PV). The PV is a parameter that needs to be controlled, such as temperature, flow, pressure, speed, etc.

PID controllers use a control loop feedback to control process variables and are the most accurate and stable controller. They're an efficient way of driving a system towards a target position or level, since they use an accurate and responsive correction to a control function.

For better understanding, imagine that you want the temperature in your office to be 77°F. That's your Setpoint (SP). The PID controller will look at your SP and compare it with the actual value of the (PV).

Back in your office, your HVAC system has a PID controller that looks at the value of the temperature sensor in the room and sees how close it is to 77°F. If the SP and PV are the same, then the controller doesn't have to do anything, and it'll set its output to zero.

But, if the SP and PV are different, then there is an error and corrective action is needed. In this case, it means that your HVAC will cool or heat your office, depending on the PV value (cooling if it's higher than the SP, or heating if it's lower than the SP).

Your PID controller will keep continue to heat or cool down your office until there's no error - your temperature is 77°F.


What is an RTU?

In telecom and IT industries, an RTU - Remote Terminal/Telemetry Unit - is a remote device that monitors and reports events occurring at a remote site. It allows you or the network operator to manage the network more effectively, keeping service flowing to your customers and protecting your revenue stream.

Some RTUs are also capable of remotely controlling remote site gear using control relay contacts or protocol-based commands.

Without this ability, an RTU can only report remote events to you. While this is valuable, you still must physically travel to the monitored location if a change must be made. So, an RTU that includes remote control capability reduces this potentially multi-hour travel to the site for a single mouse click (or even a fully automated response).


An RTU is used to provide vital information regarding the status of the equipment and other environmental conditions that are important for the site to maintain the service it was designed to provide.

In a nutshell, an RTU is a device that gives you visibility over remote sites that are vital to your business. They're used in all sorts of business, from telecom to utilities to public safety and more.


What Are The Differences Between a PID Controller and an RTU?

PID controllers and RTUs are both electronic devices that can remotely control industrial processes, such as control of machinery on factory assembly lines. Even though they seem to perform the same job, there are important differences between them that you should know about.

PID Controller Pros

Control Loops

Although PID controllers require inputs and outputs to receive information from the process and send signals back to control it, it contains specialist algorithms designed to control a process with one or multiple control loops - which RTUs don't have.

PID Controller Cons

Firmware Updates

Adding new functionality on an RTU can be as simple as updating the firmware on an existing system when a new firmware version is released by the manufacturer.

However, in almost all cases for PID controllers, if you want that new released functionality, you'll have to do a complete hardware and firmware replacement. This is because normally, PID controllers' hardware and firmware are designed and released to fit together.

Programmable

PID controllers' programmable aspect will offer you greater flexibility and freedom. However, unlike RTUs, this means that if you don't have a coder in your staff, you'll have to hire someone to perform this task. This also means that tech support is hard to obtain because simply each device will be different, and your manufacturer don't know your coding or what you are trying to achieve with it.

RTUs Pros

Capacity

RTUs are normally equipped with a larger number of discrete and analog sensors than PID controllers have.

Telemetry Area

RTUs are best suited for wide geographic telemetry, while PID controllers normally can only handle local area control.

Scalability

On the other hand, although PID controllers provide high-level algorithmic control for automation, they aren't scalable like RTUs, nor do they provide many sensors for information reporting.

RTUs Cons

Data Acquisition

The main function of an RTU is to transfer data remotely - which have more powerful communication capabilities than a controller - and not the control (even though most of the ones featuring control relays can operate as a controller).


Who is a Best Fit Costumer for PID Controller and for RTUs?

So, which device is better for you? It all comes down to "it depends." You'll need to weight in the characteristics of each device and compare them with what you're trying to accomplish.

If you need a stand-alone controller for your application, a PID controller is most likely your best choice. Just be aware that some level of programming skills might be required.

If you need a device to control multiple processes, an RTU can provide advanced control functions as it is basically a direct interface between your remote sensors and your master station.


Choosing The Best Option for Your Scenario

Whether you're better suited with a PID controller or with an RTU, it's important to know what to look for when investing your budget dollars.

Let's take a look at the best practices so you can make sure you're not buying just any device.

How to Choose a PID Controller

The best practice when choosing an efficient PID controller for your system is to take into consideration and analyze your whole network. Keep in mind the following points in order to purchase a controller that will integrate smoothly into your present system:

Features of an Efficient PID Controller

When choosing the best in class control PID controller for your system, there are a couple of features that you should look for in your device:

Auto-Tuning Feature

With auto-tuning, the PID controller automatically goes through your sensors and makes changes to the parameters based on the sensor's feedback. This feature is especially helpful during the initial setup of your device.

"Stiffness Variable" Feature

After the initial setup of a PID controller, network operators will need to make some fine adjustments to their system parameters, this often leads to some frustration because a small change to one parameter can require adjustments to other parameters that were not needed before.

That's where the "stiffness variable" feature comes in. It'll automatically make adjustments to other parameters based on changes to one individual parameters. So, if an operator make tune adjustments that would cause the system to become unstable, this feature will bring the system back into stability and avoid future errors.

Adaptive Tuning

If you have long and complicated processes, auto-tuning alone is not always an efficient solution, because it'd only provide a starting point of initial parameters. The best practice is to have your system parameters changing accordingly with the changing conditions of the process.

The adaptive tuning feature is the solution to these demanding tuning requirements. As the conditions change throughout your process, having an automated system equipped with this feature will make adjustments to various parameters if the performance crosses a particular threshold to keep the system under control and achieve the best efficiency.

How to Choose an RTU

Selecting an RTU for your remote sites means finding the right balance of capacity, interface, and features.

First of all, you'll need to perform a complete survey of your current network and remote sites. This survey will document your existing alarm monitoring situation, this way you'll select an RTU that not only meets your current requirements but is also compatible with your existing network transport.

Here are some questions that will help you start your network monitoring inventory:

You should also consider your RTUs long-term effect on your network monitoring strategy. An efficient device will both immediately improve your network visibility and support your overall upgrade plan to support your future monitoring goals.

The following questions will help you form your future network monitoring plans:

Features of an Efficient RTU

Now that we have taken a look at some of the most important factors involved in deciding which RTU to choose, let's take a look at some essential features that any high-quality RTU should offer.

Key alarm presentation and notification functions

Essential alarm sorting and analysis functions

Critical alarm collection and device management functions

RTU transport

Alarm data can be sent over nearly any kind of data transport: Ethernet LAN/WAN, dial-up modem, dedicated circuit, overhead channel, WiFi, etc.

There are two things you should keep in mind about RTU alarm data transport:


Learn More About Remote Monitoring and Control from Experts

If you are researching about PID controllers and RTUs, chances are that you're on the path of selecting a SCADA (Supervisory Control and Data Acquisition) system for your company.


The process of communication over a SCADA system involves several different SCADA system components. These include the sensors and control relays, RTUs or controllers, master units, and the overall network.

SCADA isn't just one technology. There are many different types, but they all share one thing: they give you the mission-critical data and control that you need to have in order to manage your operation.

 

So, if you've just been put in charge of selecting and/or recommending a new SCADA system for your company, you probably have many questions in mind. Where do I start? What equipment do I need? What features are essential?

Whether you decide to go with a PID controller or on an RTU, learning the basics about SCADA is critical so you can get the most out of your investment.

The SCADA Tutorial White Paper is a quick guide that will introduce you to SCADA and show you how to leverage it in your operations, this way you'll be able to answer the previous questions for yourself.

As experts in custom-made monitoring solutions, we won't tell you "Just buy this system and everything will be fine." We know that every network is different. You'll dive deeper into SCADA besides looking at the tip of the iceberg. Learn more about the different industries and their reasons for implementing SCADA. You'll see real world industries with real needs and real SCADA implementations.

After reading the SCADA Tutorial White Paper, you ultimately will be able to determine if SCADA is right for you.

Learn More

Get the SCADA White Paper

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An introduction to SCADA from your own perspective.

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