Testing the physical infrastructure with industrial Ethernet

The role of Ethernet continues to expand, supporting the high speed transfer of data and certification will play a larger role in this expansion.

By Mark Mullins August 19, 2021
Courtesy: Fluke, New Products for Engineers Database

When it comes to deploying Ethernet network infrastructure to support data transmission, certification testing is the key to ensuring that the supporting cable plant is installed correctly, complies with industry standards and will support applications.

Certification testing measures key performance parameters and compares them to industry standards set by TIA or ISO/IEC, with results indicating compliance with the standard and/or a specific category or class of cable. This, in turn indicates which industrial Ethernet applications the cable plant can support – a critical piece of information needed to leverage Industrial Internet of Things (lloT) technologies.

It is recommended that certification testing be a requirement on any cabling project specification. Indeed, it is often required for obtaining vendor warranty on the cabling system.

Unfortunately, network problems can arise after successful installation. Some of the most common causes include accidental damage to cables and connectors from workers and machinery; electromagnetic interference; miswiring or improper terminations; or dirty fiber optic connector endfaces caused by exposure to dust. There are some inexpensive tools that can help Operations Technology (OT) staff identify and locate problems.

Copper troubleshooting

A non-functioning copper link is often a result of a lack of continuity caused by a cut or break in the cable or a bad termination process. Testing for continuity is accomplished with wiremap testing that looks for opens, shorts, reversed pairs, cross pairs, and split pairs.

While the certification tester used for initial testing will conduct wiremap testing, few OT departments own these complex, expensive tools. Fortunately, verification testing using a simple, low-cost wiremap tool is an ideal solution.

Identifying the actual location of a fault along a length of copper cable can be easily achieved with an inexpensive tone and probe, which works by injecting a high harmonic signal onto a conductor that generates an audible noise at the fault location. Somewhat more sophisticated verification tools include a Time Domain Reflectometer (TDR), which indicates the distance to a cabling fault, greatly reducing troubleshooting time.

While verification is the first line of defense, if it is found that continuity is not the problem, qualification testing may be needed. A qualification tester includes all of the verification functionality but is more sophisticated and can qualify cabling bandwidth on live Ethernet networks to determine if the cable supports the intended application. A good qualification tester will indicate if the problem is related to noise issues.

Fiber troubleshooting

The most common cause of fiber-optic failures is contamination caused by dust or dirt on the endface of a fiber connector. Some inexpensive tools exist for dealing with typical problems. One tool to have on hand is a basic fiber inspection camera that can reveal a dirty fiber end face at a connection point. If dirt is visible the connector end face can be cleaned using wipes and solvents.

There is also a chance that the fiber is bent or broken somewhere along the link. A simple visual fault locator (VFL) will illuminate a fiber with a visible laser that will leak out where the fiber is broken or bent.

It may make sense to invest in a more sophisticated fault locator that bridges the gap between a VFL and an expensive optical time domain reflectometer (OTDR), which is a more complex troubleshooting tool that requires more skill to operate. There are fault locators available that locally display the location of events such as severe bends, high-­loss splices, breaks, and dirty connectors that can impact transmission.

The key to a worry-free cable plant starts with quality components and installation by a qualified installer, followed by certification testing. But if something goes wrong down the road, troubleshooting the problem can be your first line of defense. It may allow OT teams to fix the problem or at least cut down on the cost of repairs by eliminating the need to pay for diagnosis.

This article originally appeared on Control Engineering Europe’s website. Edited by Chris Vavra, web content manager, Control Engineering, CFE Media, cvavra@cfemedia.com.

Author Bio: Mark Mullins is one of the founding members of Fluke Networks, starting in 1993. He has been involved in all of the key areas of the business, including cable testing, network troubleshooting and analysis. He currently oversees the company’s global communications efforts, keeping customers and prospects up-to date on cable testing products and technologies. As a member of the Ethernet Alliance Marketing Committee, he is responsible for promoting the Gen 2 Power over Ethernet Certification program. He holds a B.S. in Computer Science and an MBA from the University of Washington.