Industrielt Ethernet   
 

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What Industrial Users Really Need from
Ethernet Communications Equipment

Introduction

As Ethernet moves from the office to the factory floor, it is important to keep in mind that the purpose of commercially available network equipment, such as an Ethernet switch, is for connecting PCs, printer servers, and other devices that are designed to work in the comfort of offices and climate-controlled corporate machine rooms. This means that if you purchase Ethernet equipment that was originally designed for office applications, but then use the equipment in your demanding industrial environment, you run the risk of causing tremendous damage to your industrial system. Because each industrial device, such as a PLC, is networked, the device plays a very important role when it comes to the operation of the entire industrial system. This is unlike the average office application, in which the failure of Ethernet equipment might merely mean that a few PCs cannot send e-mail messages for a couple of minutes. But in the industrial application, when an industrial device loses its connection to the network, the result could be a huge financial loss. When choosing Ethernet equipment to fulfill the requirements of industrial applications, and to ensure that your entire industrial system keeps running smoothly, you should keep the following points in mind:

Higher reliability, compared to office products, is essential for industrial applications

In fact, a whole new industry has sprung up to provide Ethernet products that comply with the requirements of demanding industrial applications. To ensure essential reliability for industrial applications, users should at least demand Industrial Ethernet products that come with the following features:

  • Redundant power inputs to prevent single power failure
  • Ring topology support to provide redundant path backup
  • Industrial Ethernet products built with components that are better quality and more reliable, ensuring a higher MTBF (e.g., industrial equipment does not use fans, since fans have a short life cycle).
  • The ability to withstand extreme temperature conditions, such as from -20C to 70C.
  • Industrial Ethernet products designed with a rugged high-strength case to keep out harmful substances.
  • Industrial Ethernet products that not only comply with industrial regulatory conditions (CE, FCC, UL, etc.), but also are designed to withstand shock, drop, and vibration conditions.

Providing fast recovery capability and security helps ensure continuous and safe industrial operation

The above list only gives the basic requirements for industrial applications. When considering industrial communications, reliability means more than just a strong casing and good endurance to extreme temperatures, but also involves more fault resilience functionality. In the office, a 3-minute communication failure could be passed off as a minor inconvenience, whereas in an industrial setting, the same 3 minutes could cause a tremendous loss in investment. With this in mind, the following self-recovery functions can provide the essential functionality needed to keep the network running continuously.

  • Self recovery watch-dog to prevent random service interruptions
  • Line-swap fast recovery that responds when devices change their port position, so that networked devices can keep communicating without facing several minutes of downtime

Another important consideration is that when industrial Ethernet equipment is used as part of an automation system, it is more often used to connect devices, as opposed to computer hosts. And since all automation systems incorporate sensitive devices that must be protected from unauthorized access, it is very important to have some type of authentication system set up to restrict access to authorized users.

  • Isolate selected groups of devices to prevent unauthorized access

 

Dynamic status reports that give the status of industrial equipment and devices can prevent system damages and losses

Since industrial Ethernet devices are often located at the endpoints of a system, such devices cannot always know what's happening elsewhere on the network. This means that industrial Ethernet equipment that connects these devices must take responsibility for providing system maintainers with real-time alarm messages. Even when control engineers are out of the control room for an extended period of time, they can still be informed of the status of devices almost instantaneously when exceptions occur. The traditional way of determining device status is to poll devices periodically, but this is not real-time enough, and is not very efficient as well. Warning messages must be actively triggered by events. In consideration of these requirements, industrial network equipment must have features such as:

  • Send out a warning message (e.g., by e-mail) when an exception is detected, such as when an important device is disconnected or network traffic is overcrowded

  • Provide signal outputs (e.g., digital output, relay contact) to warn engineers in the field, so they can respond quickly with appropriate emergency maintenance procedures.

Key management functions make it easy to master industrial Ethernet networks

  • Identify network segment integrity by sending a "ping" command

    Troubleshooting a network that is experiencing problems can be a real nightmare for maintenance personnel. Quick recovery from network problems is particularly important for industrial applications, since when communication is interrupted, production lines could be halted while waiting for the communication problems to be fixed. The first problem is how maintenance personnel can quickly and effectively find which network segment needs to be fixed. Being able to send "ping" commands that originate from key Ethernet equipment gives network maintainers an essential tool for diagnosing such problems.

  • Remote data scope analyzes local network behavior from a remote location

    The remote data scope utility allows users to easily monitor specific network behavior from a remote networked PC. This utility operates in a manner similar to a regular Data Scope, by allowing users to set a trigger condition, capture port data, and monitor signal status with time stamp. The difference, however, is that instead of monitoring equipment located right next to the Data Scope, users can monitor activity from a remote location, thus giving one maintenance person the ability to monitor many different devices dispersed over a wide area.

  • Assigning IP addresses to connected devices

Setting up IP addresses is one of the biggest headaches faced by maintenance personnel assigned the task of connecting industrial Ethernet-enabled devices to a network. Unlike PCs, most industrial devices are essentially a "black box," and do not come with a direct human interface. Once the network topology changes or maintenance personnel change, the bothersome process has to be repeated. Making use of Ethernet equipment that can automatically set up your devices' IP addresses can help reduce the effort.

  • Setting up mirroring ports for better online data monitoring

Sometimes a network is just too large, making it difficult to achieve the expected communications behavior. And since Industrial communications applications use more of a command-response style than the file-transfer style used in office network environments, when first setting up an industrial Ethernet network, control engineers may need to use a second port to monitor the actual activity between their devices and computer host. This "mirroring port" helps to ensure that the system behaves as expected.

  • SNMP support for easy network analysis

SNMP (Simple Network Management Protocol) is the most popular network analysis protocol used with today's network technology. In fact, it includes many types of well-defined parameters that are available to help you analyze network problems. For example, if too many packets are being broadcast over the network, causing network traffic to build up, it could be due to a device with a bad link, or because of interruptions caused by someone who connects to your network without permission. SNMP gives you the ability to obtain this type of information anytime, and from virtually anywhere.

  • OPC Server support for easy integration into your automation system

The OPC specification is a non-proprietary technical specification that defines a set of standard interfaces based on Microsoft's OLE/COM technology. The application of the OPC standard interface makes possible interoperability between automation/control applications, field systems/devices, and business/office applications. Traditionally, each software or application developer was required to write a custom interface, or server/driver, to exchange data with hardware field devices. OPC eliminates this requirement by defining a common, high performance interface that permits this work to be done once, and then easily reused by HMI, SCADA, Control, and custom applications.

In conclusion, the benefits of using industrial Ethernet technology with industrial automation systems are now generally accepted by the industrial community. These benefits include the open architecture of Ethernet and TCP/IP, as well as the continuous upgrading of technology, such as an increase in transmission speed. We have also established the fact that commercial Ethernet equipment is definitely not suitable for use in industrial environments. This means that a special type of Industrial Ethernet product is required. We not only need Ethernet equipment that has a hardened industrial design and that must work in demanding environments, but also equipment that comes with many useful management and monitoring functions. Such functions include a self recovery watch-dog, the ability to isolate selected groups of ports, and the automatic issuance of warning e-mail when an exception to regular network or device operation is detected. Additional functions that users should look for are the ability to send "Ping" commands to detect which network segment has problems, the ability to set up IP addresses of connected devices, and an implementation of mirroring ports to monitor true port activity.

In short, state of the art Industrial Ethernet products should provide:

  • The ability to keep industrial automation systems running continuously
  • Real-time alerts that provide the status of networked industrial devices
  • The capability to easily master the integrity of the industrial network
  • An industrial device oriented design

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Copyright 2002 yvind Haugland
Sist endret:  13 mai 2018
 

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