When you finish a cable installation, the customer expects it to work. So do you. If the installation does not perform to the customer’s expectations, you could end up with an expensive call back. When you have to do rework, that can mean the difference between profit and loss.
Testing provides two levels of insurance that you’ll end up with a profitable installation. If you follow industry testing standards, your first line of defense is a significantly reduced risk that anything in the installation is amiss. Second, proper testing is the key to obtaining a cable manufacturer’s warranty.
This article examines key elements of cable testing, and explains some of the potentially confusing terms that go with it. But the bottom line is this: testing is a low-cost way to avoid the potential major expense of not testing.
The right test tool for the job
Handheld test instruments (better known as test tools) are designed with a variety of focused feature sets for particular fieldwork tasks. They vary tremendously in price, performance, and application, but tend to fall into two major groups: verification or certification. Verification tools check basic connectivity. Certification tools test the cable’s performance.
Is this cable connected correctly?
Verification test tools perform basic continuity functions; they verify that the wire-pairs in the twisted-pair cables are properly maintained throughout the cable and that these wire-pairs are connected to the correct terminations. This test is called the wiremap. Some models include the connectivity test of coaxial cabling.
Verification test tools sometimes include additional features such as a Time Domain Reflectometer (TDR) for determining length of a cable or the distance to a break or short-circuit in the cable. They may also detect whether the cable under test is connected to an Ethernet switch or a hub.
Verification tools are ubiquitous, simple-to-use, low cost tools that are often the first line of defense in finding cabling problems. On the fiber side, a simple Visual Fault Locator (VFL) could be considered a verification tool as it verifies contiguous fiber connections and fiber polarity.
Figure 1 — Verification tools are simple, low-cost devices that check the basic connectivity of the installed links.
Does this cable comply with cabling standards?
Certification is the most rigorous of all cable testing. Performed primarily by commercial datacom installers, this is the final step required by connectivity OEMs to grant their warranties for properly installed cabling projects. A certification test tool makes many types of measurements across predefined frequency ranges and compares the detailed results to standards set by the Telecommunications Industry Association (TIA) {standard ANSI/TIA/EIA-568-B.1} or International Standards Organization (ISO) (ISO/IEC standard 11801:2002 Ed.2). The results from these measurements determine if a link is compliant with a category or Class of cable (for example, category 5e, category 6, Class D, E or F). Certification tools are the only tools that provide “Pass” or “Fail” information on the cabling, in accordance with TIA or ISO standards.
Figure 2 — Certification tools take very precise measurements on parameters spelled out in TIA and ISO standards. Documented results from a high-accuracy certification tool are the only means of meeting the requirements of manufacturers’ warranties.
Many certification test tools also support optical fiber test options, provide advanced graphical diagnostics and offer feature rich reporting capabilities.
Financial implications of choosing the right tool for the job
The dollars at risk are huge. The final cost-per-link of commercial installation usually averages about $100. For a large 1,000 link installation, this represents a $100,000 project. If the job is a high-bandwidth, category 6 installation, the higher quality cables and terminations typically command a 20% premium.
An installer must weigh the options of who should bear the financial risk. Using a certification tool that meets TIA and ISO standards is a requirement for establishing a warranty recognized by the cable manufacturer. Anything else makes the installer liable for the performance of that $120,000 installation. A prudent installer will want the manufacturer standing behind him.
Talking the talk
While a few electricians-turned-cable installers see testing as an unnecessary expense, the smart companies see testing as an integral investment to ensure that their installations are of consistently high quality and are consistently profitable.
And while virtually all installers agreed that testing is a critical part of a structured cabling job, no two people described testing the same way.
The terminology regarding testing can be confusing, and to some, even conflicting. Often this confusion is brought about by installers who mentally combine two seemingly similar but ultimately unrelated testing terms into a single thought. Sometimes manufacturers add to the problem by inventing new terminology to support their products.
Be careful … fancy phrases do not automatically help your business. You need to know what is really being said, and how that affects you and your customer. Here are some key terms to consider when testing to standards.
TIA
The Telecommunications Industry Association (TIA) is the standards body that is clearly focused on the structured cabling business. TIA is accredited by the American National Standards Institute (ANSI) to develop voluntary industry standards for a wide variety of telecommunications products including structured cabling being installed in both commercial and residential environments.
The TIA participates in international standards-setting activities, such as the International Telecommunication Union (ITU), the Inter-American Telecommunication Commission (CITEL) and the International Electrotechnical Commission (IEC). TIA also maintains ties with the Electronic Industries Alliance (EIA) and the Consumer Electronics Association (CEA), which are trade organizations for electronics manufacturers in the United States.
More than 1,200 individuals from nearly 20 countries -- representatives from manufacturers, service providers and end users, including the government -- serve on TIA standards committees.
T568A — The jack/plug wiring specification
Many installers are familiar with the “568 standard.” This is where the installer has to be careful. The term “568” can mean different things.
The terms “T568A” and “T568B” refer to the two color codes used for wiring eight-position RJ45 modular jacks/plugs. Both are permissible under the ANSI/TIA/EIA wiring standards, but you will not want to interchange them on the job. The only difference between the two color codes is that the orange and green pairs are interchanged. T568A wiring pattern is recognized as the preferred wiring pattern due backward compatibility issues. In short, this specification defines the wiring pattern in a jack/plug for structured cabling.
ANSI/TIA/EIA-568-B — The commercial cabling standard
The ANSI/TIA/EIA-568-B cabling standard specifies requirements for insertion loss, near-end crosstalk (NEXT) loss, return loss and other measurements related to structured cabling. In short, this standard specifies performance tests for the installed cabling links.
Both meanings of “568” are important to installers. It is equally important to know which one applies to the task at hand.
Accuracy
Many installers are familiar with digital multimeters, and have some knowledge of meter accuracy. If a DMM promises 1% accuracy, and shows a reading of 100 volts, the actual voltage could be between 99 and 101 volts.
Cabling accuracy is very different. Again, standards come in to play. For various grades of cabling, TIA defines accuracy levels for all the certification measurements mentioned earlier: insertion loss, crosstalk, etc. For Level III Accuracy, needed for Cat 6 cabling, the certification tool must be able to measure 500 microvolts (1/2000th of a volt). For Level IV Accuracy, needed for Cat 7 cable, this drops down to 30 microvolts!
Jargon Traps
Keep an eye out for terms, which sound good but mean little. “Validate” and “authenticate” both sound like official test language. However, they do not line up with terms in the TIA structured cabling standards. Bottom line … they do not have the credibility to warrant your work.
Another phrase to watch is “designed to meet standard …” Just because a product is supposed to meet a certain standard does not mean it will in the real world. Verification of specification claims by an independent, non-profit test lab such as Underwriter’s Laboratories is a good way to ensure that your product will perform as expected.
Summary
The more an installer knows about the structured cabling standards, terminology and appropriate testing, the more successful that installer is likely to be. And that translates into a healthier bottom line for your cabling installation business.
The Author
Hugo Draye is Product Manager for Fluke Networks’ Infrastructure SuperVision group. With over 20 years of industry experience, Draye frequently lectures at industry seminars and conferences worldwide including NEPCON, GigNet, BICSI and Cabling the Workplace; and is regularly published in the trade press. He holds a master’s of science degree in electrical engineering from the University of Louvain in Louvain, Belgium and an MBA degree from Seattle University.
