Ethernet for Industrial I/O: Benefits, Drawbacks, and Key Design Considerations

Ethernet for Industrial I/O: Benefits, Drawbacks, and Key Design Considerations Industrial input/output (I/O) devices make up the central nervous systems of many modern machines and, by extension, industrial plants. In the past ten years the use of Ethernet as a physical layer has been one of the most important advancements in industrial automation design for fieldbus I/O devices.

Modern EtherNet/IP (Ethernet Industrial Protocol) combines traditional Ethernet with an industrial application layer protocol targeted to industrial automation. It was created to overcome the shortcomings of traditional IEEE, which had two major problems:

Traditional IEEE wasn’t suited to handle all the complex, data-heavy processes involved in modern automation. It uses a range of various standards that can make I/O maintenance and use a challenge
In the past, fieldbus organizations created their own standards for connectors, protocols and stacks. Now, the physical layer can be handled by broad-based international standards organizations that set Ethernet standards for industrial, office and consumer environments.

Connecting I/O devices via Ethernet to control them remotely gather and parse data and monitor statuses has allowed many plants to improve reliability, consistency, and efficiency. And I/O Ethernet can play a significant role for plants looking to upgrade their lines and automation processes moving forward.

But like any technology there are pros and cons of adding Ethernet into the industrial automation design environment. To help you make an informed decision as you seek to improve your production, we have outlined the main points for I/O Ethernet below:

Pros
Cons
Ethernet vs. Other Options
Best Practices

PROS of Ethernet for I/O

Networked I/O, using Ethernet, has provided improved better performance, flexible topology and simpler configuration as well as a range of other advantages.

Faster Processing – Ethernet I/O makes it possible to run real-time updates in less than a millisecond. The higher processing speeds create efficiencies in data collection and analysis, a crucial building block for data-heavy industrial automation.
Standardized open communications protocols for industrial automation design – Ethernet is used in combination with open-source, standard protocols, such as EtherCAT, Profinet, EtherNet/IP, Powerlink and others. And all of them can easily interface into many devices, such as drives, encoders and industrial controls on the I/O network. As fieldbuses have become more open and dependent upon known physical technologies like Ethernet, I/O network update rates have increased to the point where they can keep pace with real-time events in the control system.
Less Copper — Lower Costs – Previous IEEE networking required significant amounts of copper wiring for industrial devices. But today, connecting I/O devices to the controller requires only the I/O network connection, control power and, in the case of high-energy devices, three-phase power. This eliminates ground loops and messes of copper wire. Instead, one standard cable connects the controller to the industrial operating system, which can be located far from its controller and be distributed.
Protection from Platform Obsolescence – Because Ethernet is available for virtually every hardware platform in existence, it’s not tied to any one manufacturer or even class of equipment. It will continue to work for the foreseeable future, providing a future-proofed investment in connectivity, which also has the benefit of bolstering long-term security.
Reliability – Ethernet I/O works reliably in harsh environments, like those in solar power plants, oil & gas refineries, railways, wind power plants and even marine facilities. Odds are, industrial automation design using Ethernet I/O will meet that demanding needs of your production environment.
Common, certified standards and wide vendor support – Industrial Ethernet uses the transport and control protocols from traditional Ethernet and the media access and signaling technologies found in off-the-shelf Ethernet interface cards. It’s a robust, certifiable standard that allows great flexibility in equipment use while ensuring devices are certified, tested and approved by EtherNet/IP test labs to ensure their quality and consistency. The core of EtherNet/IP is the Control and Information Protocol (CIP) used in ControlNet, DeviceNet, and CompoNet. This standard organizes networked devices as a collection of objects, defining access, object behavior and extensions. This provides access to a massive range of devices using a common mechanism, and because it’s such a widely used standard, — every industry uses Ethernet — there’s extensive vendor support for nearly any type of I/O device.
Simple, Fast Setup – Ethernet provides producers more options, whether it’s safety, fieldbus, less programming or web servers. It allows plants to move between protocols or implement a fieldbus for the first time in simple, plug-in fashion. Many products are self-configuring, as they automatically recognize the master protocol.
Other Benefits – Some additional minor benefits of industrial automation design with Ethernet for I/O include: Single (or pair for high-availability) interconnect for networking and storage I/O; Power reduction, more efficient cooling and floor space use and a more sustainable plant environment; Server performance improvements, maximizing PCI and mezzanine slots; Better scaling of I/O capacity to handle high-performance and clustered application needs.

Cons of adding Ethernet for I/O

Now that we’ve extensively covered the benefits of Ethernet I/O, we’ll discuss some of the biggest drawbacks:

Bandwidth Limitations – Ethernet I/O has limited bandwidth. Many PLCs can only move packet sizes of around 500 bytes, which can be a significant hurdle at times, potentially slowing down operations.
Processing Gets Eaten Up by TCP/IP Layers – EtherNet/IP is an application layer protocol that’s transferred inside of a TCP/IP Packet. That means significant processor bandwidth goes to the processing of the TCP/IP layers, again slowing down performance.
No Information Modeling – With Ethernet, there’s no true information modeling. You can create objects with attributes but can’t link objects together into any sort of hierarchy. This can create some challenges in real-world implementations of industrial automation design.
Equipment Variation – There is limited functionality to Ethernet with certain controllers, so you still need to be careful about selecting the best equipment.
Overpowered – In many cases, Ethernet is best used for discrete control applications. It can work in process control, scenarios but it can be an over-powered solution that unnecessarily eats up too much budget. In some cases, more practical, less costly solutions exist.
Diagnostics – Generic diagnostics aren’t built into all Ethernet devices. Each device may need to have its own custom diagnostics designed and implemented, which can take up significant time.

Comparison of Ethernet to Other Technologies

Attribute	I/O Strategy
Attribute	Host-resident	RS-232	RS-485/422	Ethernet
Ground Loop Tolerance	Poor	Fair	Fair	Excellent
Standardized ISO Protocol Layers	None	Layer 1	Layer 1	Layers 1-3
Communication Data Rate	Excellent	115 Kbps	10 Mbps	10-1000 Mbps
Platform Life Expectancy	Poor	Good	Good	Good
Expandability	Poor	Poor	Fair	Excellent
Standardized Connector	None	DB9 or DB25	None	RJ-45
Host Computer’s Cable Congestion	Poor	Fair	Good	Good
Host-to-I/O System Distance	Poor	Fair	Excellent	Excellent

Crucial Things to Know

When transitioning to Ethernet I/O, it’s critical to assess a wide range of features to get the right sort of Ethernet. Consider the following Ethernet IOS architectures:

Ethernet Per Module Systems
Module Carrier Systems
Star Cluster Systems

Essential Features

Aside from its architecture, every Ethernet IOS has important functional features that must be evaluated. Every industrial IOS must provide some level of support for the following common functions:

Power monitoring
Power distribution
Interlock support
Environmental Protection

We can help

The choice of Ethernet protocol depends on many factors. But most of the time, the PLCs used in your facilities and your customer demand will drive your decision. If you use Siemens, Profibus DP or ProfiNet IO may be your best options. If you’re with Rockwell ControlLogix or CompactLogix, EtherNet/IP or DeviceNet are your best choices. Your application requirements and current infrastructure will drive decision-making.

At EPIC, we have deep expertise across a wide range of systems and technologies, and we’ve helped plants worldwide. If you need expert assistance in selecting the best technologies for your plants industrial automation design, we can help.

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