Published: February 2004
Voice/data/video systems cannot be cabled and maintained without testing, and installers today can choose from a broad range of test tools that include basic testers providing simple “go/no-go” results and sophisticated diagnostic tools able to examine a variety of parameters and certify that a system meets industry standards.
• Toners and probes. Toners inject a frequency on conductors within a cable, and probes sense the frequency to locate cable behind walls, in bundles or in closets. Some toners and probes perform basic continuity tests and some can do polarity testing.
• Cablemappers examine conductor continuity and test for basic miswires that are pair based, such as reversals and rolls. Cablemapper features are integrated with higher-performance testers as part of certification.
• Wiremappers provide comprehensive testing, including cablemap functions, while also testing for split pairs, and they perform complete verification testing as called out in the ANSI/TIA/EIA 570B draft standard.
• Certification instruments test twisted-pair cabling over a specified frequency range to meet standard requirements. In many cases, they are used to certify Category 5e or Category 6 standards installations.
While the ability to accurately test system basics is important, sophisticated VDV tester models offer diagnostic capabilities that simplify the trouble-shooting process and help reduce project costs.
“On any project, if the materials are good and installation practices are correct, testing should result in a pass,” said David McLean, marketing manger for Fluke Networks. “But what if things go wrong? A good tester is also a good diagnostic tool. Testers with troubleshooting capabilities can shave diagnostic and repair time of tested cable to minutes.”
John Olobri, director of sales and marketing for AEMC Instruments, said: “It is common today to find fault finding, cable tracing, signal speed and length measurement as well as wiremapping in a single unit for under $500. Graphic displays greatly enhance the operator’s ability to quickly troubleshoot twisted pair, coax and basic electrical wiring.
“Cable testers range from a simple go/no go devices with red and green LEDs to sophisticated models that check speed, dB loss, impedance and a whole host of other parameters,” Olobri continued. “For basic function testing looking for proper pin outs, opens and shorts, one tester can be used for both twisted pair and coaxial cables. More sophisticated testing may require different instruments.
“Testing newly-installed VDV systems offers the installer the ability to certify that the job is complete and functioning properly before turning it over. This can save considerable time and money later on.
“The need for certification is going to increase,” Olobri said. “This will require more analytical testing tools that will analyze the quality of the signal as well as the wiring conditions.”
Fluke Networks Marketing Manager David McLean said: “Basic verification testing of continuity and wiremap allow installation professionals to assure their customers that their wiring infrastructure ‘turns on.’ Certification testing confirms that the performance of the installation is as intended and is the only way to confirm that the raw components that you have assembled meet Category 5e or Category 6 standards. Networks can pass verification testing, and fail certification testing. Upcoming in the ANSI/TIA/EIA 570B draft standard is a type of performance testing termed ‘qualification.’ This testing type will be important for residential networks in 2004.
“Depending on the sophistication of the testing to be performed, coaxial cabling may be tested with a combined unit for twisted-pair and coaxial cable testing, or coaxial cabling may only be able to be performed by a standalone test instrument,” McLean said. “For example, many test instruments test for continuity and ensure there are no shorts or grounds. Another type of test instrument that may work for twisted-pair and coaxial cabling could also test for the signal level being delivered to a system. Other test instruments are standalone and can scan frequencies that may be in excess of 3 GHz, and they take appropriate readings to ensure there is not sufficient leakage or ingress of signal to the coax cable to cause impairments.
“Multipurpose test instruments are in demand,” McLean continued. These include those that test twisted-pair, coax and optical fiber. By making a simple change of an adapter and invoking different software limits, the use of one instrument makes it easier for the installer to test and incorporate the results into one report.
“The evolution of test instruments is dependent on standards requirements. For instance, significant work is being done for a 10GBASE-T standard, which will likely increase the frequency limits currently offered in test instruments today. To ensure cabling will meet these rigorous standards, equipment may also need to be changed.
“Test instruments change with industry standards. For example, verification testing requires a wiremap result,” McLean said. “Standards have not changed this requirement. Certification test results, on the other hand, change according to current standards. Standards drafts are used to calculate results and may change over time and should be updated through firmware uploads into test instruments.”
Rob Bentley, product manager for Greenlee Textron, said: “Functionality and feature sets vary widely from one test set to another. The simplest test sets perform a basic continuity check. Basic wiremap tests look for opens, shorts, crossed transposed and reversed pairs.
“Display methods of either pair-to-pair or pin-to-pin styles (pair-to pair is most common) requires that instrument users to have knowledge of correct wiring configuration and requires some interpretation of test results. Many testers still only test UTP cable, and as Category 6 becomes more widely used, testing shield continuity on STP will be necessary.”
Split-pair detection is becoming a more common feature in low end testers, Bentley said. “With higher speed data transfer a split pair becomes more of an issue that must be dealt with. For length display, the tester uses either TDR or the capacitance method to measure distance to a fault or to the end of a cable.
“Improvements in manufacturing and competition have brought lower prices in tester equipment,” he said. “Lower cost LCDs mean more information can be displayed and presented more clearly.”
Caroline Chen, Ideal Industries Inc. product manager/datacomm test equipment products, said, “Testers are more complex, sophisticated and yet they malfunction less today than ever before. This is a result of standards that require greater network performance of cable that must be tested and advances in microprocessors and electronic components. Testers today are easier to use, many with simple push-button icons. Indeed, many testers are designed for people who do not read user manuals.
“Simple, all-purpose, handheld instruments typically test a network at a passive stage before active components are installed. With 80 percent of wiring problems resulting from poor termination, a wiremap test should detect open, short or split terminations.
“Testing for length is another important feature,” Chen said. “For example, you know you have a problem if three out of four pairs of the Category 6 cables are measured approximately the same length but the fourth pair is measured at an unusual length. To support multiple cables, one should look for a tester with RJ45, RJ11/12 and coaxial interfaces. To make testing an easy one-person operation, these testers should include remotes so one person can test terminations at multiple rooms from a single distribution location. Finally, look for testers with easy-to-use push-buttons and easy-to-read screen display.
“Sophisticated handheld passive network testers can test the cable types to standards such as TIA/EIA/ISO specifications, and you can expect a tester in this type to support multiple types of cable including fiber,” she said. “Many of these can troubleshoot distance to fault, in addition to a full suite of tests, specified by the standards, to identify potential wiring problems. Unlike the simple all-purpose testers, this type of tester can usually generate reports providing documentation.
“Once a network is up, it must be maintained,” Chen said. “The biggest part of the network maintenance is move-and-add services. Testers for active network diagnostics are used in conjunction with other test tools and may have link-layer testing capability such as PING to test connectivity, in addition to many of the same features as other testers.”
Sophisticated VDV systems are nothing new on commercial projects or at Enterprise facilities, and projected growth is expected in those markets. In addition, Chen says marketing research indicates significant potential for growth in VDVs for private residences.
By 2004, she said, some studies find that more than 48 percent of all new homes in the United States will be pre wired for voice/data/video capabilities, along with automated control lighting, heating and cooling, and security systems.
“The market for home wiring installation is expected to grow more than tenfold in this decade to support both new construction and retrofit home updates,” said Chen.
“Homeowners are sophisticated consumers who want hassle-free service for voice, data, high-fidelity entertainment, security, and HVAC control capabilities at their finger tips inside their homes or from remote locations. To support these applications, the VDV systems must be tested as part of the overall installation process for both new and retrofit installations.” EC
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or firstname.lastname@example.org.