Testing Copper Cabling: Verify, Qualify, Certify
The Continental Automated Buildings Association and Communication Planning Corporation have developed a cable test guide to assist you in testing copper cabling. The excerpt below examines the types of tools available for proper testing.
Copper testing tools can be classified into one of three broad hierarchical groups – verification, qualification, and certification. There is also a fourth category but it is not actually a tool: Visual inspection for each cable run after the cable has been pulled in and prior to termination lets you check for factors such as damage to the cable and incorrect bending radii. Visual inspection of all cable runs and immediate repair of obvious errors will eliminate needless troubleshooting later.
Verification tools are often used by network technicians and contractors as a first line of defense for cable troubleshooting. Verification test tools allow you to see if each wire pair in the cable is properly connected.
Verification test tools perform basic continuity functions (for example, a wiremap test, toning). These verification test tools sometimes include additional features such as a time domain reflectometer (TDR) for determining length to the end of a cable or to a trouble spot (open connection or break) or short circuit. They may also detect if a switch is connected to the cable under test or check coaxial connections.
Verification tools are ubiquitous, simple-to-use, low-cost tools that should be the first test for new cabling installations.
Qualification tools are more sophisticated tools that network technicians use to troubleshoot and qualify cabling bandwidth. Qualification test tools give you the information you need to decide if existing cabling will support your technology requirements like 100BASE-TX, VoIP, Gigabit Ethernet, and others. For example, let’s assume you have two cables of unknown capability. Both cable A and cable B pass the verification wiremap test. However, a qualification test may show that cable A is only capable of supporting 10BASE-T, while cable B is able to support 1Gb/s Ethernet.
Qualification tools are much more powerful than verification tools and are designed to enable even the most novice technician to see the data rates that an existing cabling link can support to quickly isolate cabling problems from network problems. This means network techs can close trouble tickets faster and reduce on-call time. However, qualification tools do not perform certification required by cable manufacturers.
A unique feature of many qualification test tools is the ability to diagnose
common cabling problems that may limit the cabling bandwidth. An example of
information provided by the qualification tester is the distance to an impedance mismatch where two cables are joined. Now the user knows what level of performance the cable can support, the reason the performance is limited, and what needs to be done to fix the problem.
Certification test tools demonstrate if a cable complies with cabling standards (such as TIA-568-B Category 6 or ISO 11801 2nd Edition Class E). These tools are used by commercial datacom installers/contractors and enterprise facility managers, and are required by cabling manufacturers to ensure that a newly installed cabling system fully meets cabling standards and the cabling manufacturer’s warranty. Enterprises often require certification testing before signing off on an installation. Certification is the most rigorous of all cable testing.
A certification tester takes many types of measurements across predefined frequency ranges and compares the detailed results to standards set by the Telecommunications Industry Association (TIA) or International Standards Organization (ISO). The results from these measurements determine if a link is compliant with a category or class of cable (for example, TIA category 5e, category 6, or ISO Class D).
Certification tools are the only tools that provide “pass” or “fail” information on the cabling, in accordance with TIA or ISO standards. Additionally, certification testers commonly support optical fiber test options, provide advanced graphical diagnostics, and offer feature-rich reporting capabilities.
Testing the Permanent Link Versus the Channel
When a new cabling system is installed, the installation crew is typically not responsible for the patch cord or equipment cords. This crew pulls the cables, labels and terminates them, and certifies the performance of the permanent link. The permanent link (PL) is that portion of the installed cabling that becomes a permanent part of the infrastructure in the building. The cable itself is routed though hidden pathways within walls, under floors, and in ceilings or in cable trays and conduit. Upon completion of the installation, each permanent link is certified from the termination in a telecom room patch panel to the telecom outlet or jack in the work area or office at the other end. The PL is a subset of the linkage between network devices. It does not represent the complete end-to-end connection between network devices.
Most modern certification test tools offer the choice to certify the PL or the channel. Testing the channel would be acceptable if you can guarantee that the patch cords used for the channel certification are going to remain in place for the life of the cabling system – a very unlikely scenario – or you make the commitment to re-certify each channel whenever patch cords are replaced or exchanged.
For this reason, the PL test is used most often. It offers two significant advantages:
- The PL certification fits with the typical installation process as described above. The installation crew seldom, if ever, deals with patch cords. And with any greenfield installation, it is impractical to even consider leaving patch cords attached to each outlet.
- Proper testing of the PL delivers true results of the permanent link performance and guarantees that a passing PL will yield a passing channel when known good patch cords are attached to create the channel. This is true for category 3 cabling and for all other levels of performance including augmented category 6 (Cat 6A) cabling.
Knowing that a test failed is only the first step. The link must be fixed so it will perform as intended. The reasons for failing certification tests fall into two distinct categories –connection problems and transmission performance problems. There are many tools that can provide information regarding the connection problems such as an open, a break, a short, etc. The user should select a tester that can properly locate a break or a short in the cabling as well as identify problems caused by improper pairing of the wires. In addition, certification testers should include advanced troubleshooting diagnostics that identify and locate transmission defects. With this diagnostic information, the installer can dramatically improve troubleshooting productivity and help to restore service quickly.
To read the cable testing guide in its entirety, click here.
The Continental Automated Buildings Association (CABA) is an international not-for-profit industry association dedicated to the advancement of intelligent home and intelligent building technologies. The organization is supported by an international membership of nearly 400 companies involved in the design, manufacture, installation, and retail of products related to home automation and building automation. Public organizations, including utilities and governments, are also members.
Communication Planning Corporation provides experienced technicians and creative solutions to bring exceptional service to its customers since 1980. From sales professionals to certified design engineers, project managers, and support personnel, its team can evaluate customer needs and provide a comprehensive package comprising telephone systems, VoIP, structured cabling, data networking, CCTV, and audio and video conferencing.