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Certification testing is key to a functioning network infrastructure

Dec. 8, 2020
In this installment of Automation Zone, learn about several inexpensive tools that are available to check the cabling runs that keep your operations going.

When it comes to deploying Ethernet network infrastructure to support data transmission across both back-office networks and throughout your manufacturing plant, certification testing is the key to ensuring that the supporting cable plant is installed correctly, complies with industry standards, and will support your applications.

About the Author: Mark Mullins

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 you may need in order to leverage emerging IIoT technologies, which are paving the way for significant benefits across plant operations.

It is therefore recommended that certification testing be a requirement on any cabling project specification. In fact, it is often required for obtaining vendor warranty on the cabling system. It’s also your best option for complete peace of mind.

After an installed cable plant has been certified, there shouldn’t be much of anything to worry about – especially if you’re working with a reputable installer and using quality components specifically designed for your industrial environment. However, the fact is that network problems can arise that are related to your physical infrastructure.

Some of the most common causes include:

  • accidental damage to cables and connectors from workers and machinery
  • electromagnetic interference from the addition of new noise sources in proximity to copper network cables
  • mis-wiring, improper terminations or other errors during moves, adds, and changes
  • dirty fiber optic connector endfaces caused by exposure to dust.

If something does go wrong, the good news is that there are plenty of simple, inexpensive tools that can help your operations technology (OT) staff identify and locate the problem.

Copper troubleshooting

A completely nonfunctioning 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:

  • Opens are typically caused by broken conductors either within the cable or at the point of termination.
  • Shorts tend to indicate improper termination or a damaged connector.
  • Reversed pairs occur when two conductors of a pair swap pins of a pair position at one end.
  • Crossed pairs occur when a pair is connected to a different pair position at one end.
  • Split pairs occur when conductors of a pair become separated due to one conductor being connected to a pin of a different pair position.

While the certification tester used by your installer 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.

Some of these verification tools feature a built-in tone generator. Other considerations when selecting verification tools include:

  • types of cables and connectivity supported (e.g., twisted-pair, coax, and audio)
  • distances supported
  • graphical display to easily identify wiremap issues and location of a fault
  • ability of a probe to filter out signal interference from common 50 or 60 Hz noise sources.

While verification is your first line of defense, if you discover that continuity isn’t the problem, you might need something a little bit more. That’s where qualification testing comes in. A qualification tester includes all 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, which is caused by dust or dirt on the endface of a fiber connector. Unfortunately, manufacturing plants are often dusty environments that can wreak havoc on an exposed fiber endface. Fiber testing requires more expertise and costlier tools, which is why many plant managers delegate fiber issues to contractors. However, some inexpensive tools exist for dealing with typical problems.

If you’re dealing with fiber, one tool to have on hand is a basic fiber inspection camera that can easily reveal a dirty fiber endface at a connection point. If dirt is visible and your OT team has the skillset, it’s time to clean the connector endface using wipes and solvents. Ideally, any solvent used to clean the connector should be formulated specifically for fiber, so it makes sense to have a fiber optical cleaning kit in your arsenal.

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. However, a VFL only works well if you can visually inspect the entire fiber run – not so great if the fiber is difficult to access or goes through protective conduit.

For just a little more money, 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. For example, 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.

Keep it simple

Again, 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 with simple, inexpensive tools can be your first line of defense. It may allow your OT teams to fix the problem or at least cut down on the cost of repairs by eliminating the need to pay for diagnosis.

Just remember to keep it simple: if your OT team can’t easily identify, locate, and fix the problem, it might be time to call in the experts with their sophisticated network certification testers and OTDRs.

Automation Zone

This article is part of our monthly Automation Zone column. Read more from our monthly Automation Zone series.

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