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Testing: How to Make Your Data Cable Installation Do What You Told Your Customer It Would (4/9/2006)

By Christian Schillab, Fluke Networks

Home PC ownership continues to grow, and consumers' appetite for digital devices such as cameras, camcorders, MP3 players and so on, shows no sign of abating. That means that there is more and more digital data, such as pictures, music and films, that needs to be stored and shared among multiple PCs and other devices in the home.

This is driving growth in the market for residential data cabling installation. It makes sense, logistically and economically, for the contractor who installs and connects home electronics equipment to also install data cabling. And just like an electrical wiring job, data cabling must also be tested on completion to ensure that it has been installed correctly and functions properly. This article shows the kind of tests that can be done on a data cable installation, and what faults the tests are likely to reveal.

Industry standards

The categories and classes of cable used in data networks are governed by industry standards. By complying with these standards, you can give yourself and your customers confidence that your installation is correct. Not only that, it is worth remembering that a cabling installation should have a useful life of ten or more years. During that time, the electronics inside PCs and other networked devices is likely to advance several generations. By complying with industry standards, you give the network you install the best possible chance of supporting new, faster networking protocols in future.

In physical terms, data cabling is generally of two types: 'twisted pair' copper cable, or fibre optic cable. Fibre supports higher data transmission rates, but is more expensive to buy and more difficult to install. Nearly all home users' needs will be easily satisfied by copper cable.

Industry standards such as the ISO/IEC standard 11801:2002 and the TIA/EIA standard 568-B describe and define the measurement methods for the field certification of installed data cabling. These standards define cabling systems with different performance specifications. The cabling components, i.e. the cable, and the jacks and sockets used to connect them to a device such as a PC, are described in 'categories' such as Cat 5, Cat 5e, Cat 6 or Cat 7. As the category number increases, so does the performance - as does the price of the components.

Today, most new business installations use Cat 5e cabling. Many home users will do likewise, as it supports Gigabit Ethernet networking. A Gigabit Ethernet network transmits data at a theoretical maximum speed of 1Gb/s. Such a network could therefore, for instance, transmit the entire contents of a CD, in MP3 format, in less than a second.

Testing the physical cabling: verification test tools

Just because you buy, say, Cat 6 cable and connectors, does not mean your installed network will provide Cat 6 performance on installation. To be sure that it does, you will need to test it after installing it. And for that, you will need some kind of test instrument. The most basic tester is a verification tester. A verification test tool performs four basic functions:

Wiremap

Wiremap tests the end-to-end continuity on all four-wire pairs to quickly verify if the cable under test has the correct 568A or 568B wiring scheme, and to identify any cabling connection problems. A verification tester needs to identify faults quickly, allowing the user to see opens or breaks, shorts, crossed pairs, split pairs or any miswires.

Note that many very low-cost testers will not detect a split pair wiring error, which may allow a link to work with low speed data transfers but will be completely useless at higher speeds.

Length

If a fault is found in the wiremap, the installer needs to know where the fault is so it can be fixed. Time is often wasted with visual inspection. A more direct route is to use a verification tool that tells the user whether the cable is open or shorted and the distance to the fault. Many testers provide highly-accurate length information.

The Fluke Networks MicroScanner Pro confirms continuity, wiring configuration and the location of a cable fault

Cable Identification

A verification tool needs to help the installer identify cables. A toner and probe set will do this, but there are some limitations. Firstly, a toner and probe will only work with one cable at a time. Secondly, some types of probes are highly susceptible to electromagnetic interference, making them difficult to use in electrically-noisy environments. Newer toner and probe sets inject a digital pulse on the cable. The probe responds only to this unique digital signature, thus eliminating interference problems.

Wire types

While multi-conductor twisted-pair cabling is the predominant medium, there are times when having the ability to test coax and two-conductor wire can be a major time saver. A versatile verification tool should have the ability to test multiple cable types as either a standard function or through easy-to-use adapters.

Verification testing is based on the assumption that the components used are compliant and only the correct wiremap and end-to-end continuity need to be verified. Unfortunately, verification testing will fail to discover any noncompliance due to bad workmanship such as untwisting, improper handling of the shield and ground, or abuse of the cable.

Certifying the performance of the cabling

Certification is the most rigorous of all cable testing. Performed primarily by commercial datacom installers, this is the final step required by the manufacturers of cable and connectors to grant their warranties for properly-installed cabling projects. While it gives you a cast-iron guarantee of the performance of the installation, certification testers are priced beyond the reach of all but a very few residential installers.

This dilemma typically results in a philosophy of 'Terminate, Walk and Pray'. While the chances are small that the homeowner will contact you with the complaint that 'the link number 4 to the family room does not fully meet Class D requirements', there is a realistic risk that they will say, 'I just bought a new 1000Base-T switch. When we connect the PCs directly they work perfectly but the IPTV video streams look terrible. You better come back and check this out.'

Qualification Tools

In response to this need, the new TIA-570B residential cabling standard now calls for 'qualification testing'. The qualification method allows installers to test and document that any cabling link will support the data needs of residential networks such as 100Base-T (offering a maximum 100MB/s data rate), as well as applications such as CATV, voice-over-IP (VoIP), audio/video and security/alarm networks.

Table showing the different capabilities of verification, qualification and certification tools

Results are stored in the test unit, and can be uploaded to a PC, printed out and provided to builders or homeowners. Qualification testers such as the Fluke Networks CableIQ Residential Qualifier also have powerful installation, verification and troubleshooting capabilities. These allow residential installers to replace multiple tools for testing and ID-tagging all voice, data, video, audio and security cables and outlets with one convenient unit.

The Fluke Networks CableIQ Residential Qualifier allows installers to document that cabling systems are installed properly

How is qualification testing valuable for residential installers? The key to qualification testing is that it provides an economical way to document that cabling installations are defect-free, and will meet the builder's expectations for quality and reliability. Getting called back to jobs is expensive, and avoiding them yields bottom-line savings.

Ensuring an installation's compliance with TIA-570B standards allows installers to virtually eliminate these expensive call backs. Absence of documentation also often results in disputes over the cause of cabling problems. These disputes are embarrassing and damage the credibility of installers. Professional qualification test reports prove the cause of cabling failures and eliminate disputes.

Conclusion

When you finish a cable installation the customer expects it to work. You need it to as well, because 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 on the job.

Testing provides assurance that you will end up with a profitable installation. Industry testing standards have been field-tested and proven. If you follow the standards, you are giving yourself the best possible chance of completing an installation that works first time.

There is an initial investment to be made in buying a high-quality verification or qualification test tool, but that investment will soon pay off when you complete installations faster and with greater certainty that they will work perfectly.

Christian Schillab is EMEA Product Manager for the Infrastructure SuperVision product line of Fluke Networks. Fluke Networks provides innovative solutions for the testing, monitoring and analysis of enterprise and telecommunications networks and the installation and certification of the fibre and copper forming the foundation for those networks.

www.flukenetworks.com