Submitted by: Colin Yao
Unlike electrical conductors, telecommunications conductors need more than a sound physical connection. The conductors must also maintain their shape and layout all the way to the connector, or signal distortions can occur.
Proper tools are necessary and practice is required. Termination of telecommunications cables requires testing and documentation at the time of installation.
To test the link, use one of the recognised hand-held Cat5E and Cat6 cable testers. Follow the manufacturer’s instructions and ensure that the test leads used are the correct ones.
The particular model chosen must be specifically designed to test installed cable to Category 5 or 6 standards.
Older versions of cable testers that can only measure Category 5 parameters to the original 1995 specification are know as level II. To measure the new enhanced or Cat5e parameters Level IIE testers are required.
Category 6/Class E measurements require a Level III tester.
>> Preparation Before a Copper Cable Test
Here are the preparations that must be done first:
1. Agree with the user what percentage of the installation to be tested.
2. Agree with the user how the test results are to be presented.
3. Agree with the user how marginal fails will be handled
4. The cable must be tested in both directions. It is assumed that the tester will have a remote injector facility.
>> Cat5E and Cat6 Cable Tester Capabilities
The copper cable testers usually come in a main unit and a remote unit. Without the remote, the tester inspects the line for shorts, opens and split pairs. Used with the remote, the tester tests for miswires and reversals, too.
Here are some of the most common features in a Cable Tester:
1. Wiremap, ID, and faults display on a LCD screen.
2. Tests Cat3, Cat4, Cat5, Cat5E and Cat6 UTP and STP cables.
3. Determines cable lengths, identifies multiple faults, and shows clear Pass/Fail results on an LCD
4. Tests for shorts, opens, miswires, reversals, and split pairs.
5. Cable test results are displayed in wire map format with a message line for shorts and split pairs.
>> Most Common Wire Errors
The wire mapper will indicate a short where two conductors are accidentally connected.
Open occurs where one or more wires are not connected to the pins on the plug or jack. Opens can also occur due to cable damage.
Most shorts and opens will occur at the connections. Physical examination of the connections should find the fault. If possible, unpatch the cable in a link to help the location. A TDR test will show the distance to the fault to assist you in locating it.
3. Split Pairs:
Some wiring verifiers will provide basic connection information, but some faults like split pairs may not show up in their wire maps. Split pairs occur where one wire each of two pairs are reversed on both ends. This is impossible to find with a normal wiring verifier, because the wire map is correct – that is, the pin connections are correct, but the wires are not in proper pairs. This error can only be detected in a NEXT test or balance test, where the unbalanced pairs can be detected.
>> What is Cable Certification
If a cable-certifying tester is available, test your cable link with it. This tester does much more than a wire map; it measures length, attenuation, crosstalk (NEXT), and ACR per EIA standards.
Generally, these testers are set up to provide a “pass/fail” test for the link and only display more information if the link fails a test.
The most common failure in cat5E/6 performance testing is NEXT (Near End Cross Talk), generally caused by untwisting the pairs too much at a punchdown block or jack. Most other performance parameters are a function of the manufacturer of the cable, so no failures should be expected from pretested Cat5E/6 cable.
If you have a NEXT failure, check pairs at all punchdowns, including the back of jacks, for too much untwisted wire. If that does not appear to be the problem, look for bends or kinks in pairs. If you are using modular adapters to connect patchcords, make certain they are Cat5E/6 rated, because normal phone connectors will always fail NEXT.
About the Author: Colin Yao is the sales manager at Fiber Optics For Sale Co. Get
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