Test equipment: Using a CAT5 cable tester to find common wiring faults

test equipment T3 Innovation

by Jason Chesla, T3 Innovation

Cable test equipment: We all know that Cat5 cable is an abbreviation for Category5, which is defined in the ANSI standards as cable which satisfies certain performance characteristics for frequencies up to 100 MHz. It is comprised of twisted pair cable for carrying signals in computer networks, telephony applications, and video, and is most often connected via modular connectors or punchdown blocks.

Cat5 cable is generally unshielded and relies on its balanced line twistedpair design, coupled with differential signaling to minimize inherent noise. While Cat5 cable works very well in the applications described above, that does not mean it is completely free of problems, because wiring mistakes are often made accidentally which can significantly compromise the integrity of the cable itself.

Common wiring faults can be a pain to identify, so when you purchase a cable tester, you should find one that can clearly display the results, and measure the distance to an open or a short. A color screen can also be a big help, because it can help to identify the cable color code, which will make it easier to reterminate the connectors after you've fixed the problem. Some of the most common wiring mishaps are described below, along with potential solutions.

Wiring opens
Opens are usually caused by bad termination which is why it is very important to use a cable tester that measures distance to opens. O pen circuits are one of the most common wiring problems in existence, and they are caused by broken wires, open connectors, nonoperational switches, and bad terminations. In essence, an open circuit is created when any point within the circuit offers resistance so high that current cannot pass through it.

To test for an open circuit, identify some easily accessible areas to measure voltage, and place one probe lead on the wire in the circuit, while the other is connected to ground. If your meter displays source voltage, it means that circuit voltage is being dropped between the two leads as it should. While keeping the ground lead in place, keep moving the circuit wire access lead closer to the ground lead until you find a point where voltage measurement is negligible. That will indicate the open circuit is somewhere between the last two access points in your circuit.

Wiring shorts
Shorts occur for various reasons, such as when a drywall contractor puts a screw through the cable accidentally, or when the installer cuts through the installation while stripping back the cable jacket. Having a cable tester that can measure the distance to a short, can help you find where the damage is. In a short circuit, electricity flows directly to ground and with much more current, because there is no resistance.

Miswiring occurs when the wires are terminated in the wrong place. A close examination of the wiring diagram, compared to the existing wiring configuration, should point up any errors related to cables being improperly terminated. Correcting the problem shouldn't be any more difficult than reterminating the cables to the proper pinout, and retesting.

Wiring Split Pairs
Split pairs occur when pairs are terminated in the wrong order, so that two wires fromi fd ferent twisted paiarsr e linked together. This commonly introduces crosstalk into the line, or in the case of a video line, significant interference. A good place to start checking for a split pair is at the network interface, so as to be sure the signal from the utility company is good, and that the problem can be isolated to the private user. Your cable tester can be used to identify split pairs on cables that appear to have mismatched color codes.

Troubleshooting common wiring faults
Finding the most common wiring faults used to be much harder than it is today, but much of the difficulty has been relieved by color coding of all cables used in telephony these days. In addition, cable testers have become much more sophisticated in the kinds of functions they are capable of, and can eliminate much of the hassle in finding wiring problems. With a sharp pair of eyes, and a good cable tester, the technician's job of finding frequently occurring wiring mistakes has been made much easier.

How Cable Prowler can help find wiring problems
The Cable Prowler cable tester from T3 Innovation is a device which can be used for fullcolor cable testing, storage of test results, and printing of those results for Cat5, 5e, 6, and 6a telephone cable. It combines the functions of a highend cable tester and length measurement tester all in full color, and is equipped with its own internal memory so all results can be saved.

It is also equipped with numerous features that any installer or technican will have need for an almost a daily basis. It can test ethernet cable configuration and verify connectivity, while testing for opens, shorts, miswires, split pairs and reverses to make your job much easier. With the Cable Prowler, you might not need any other troubleshooting tool to find all the most common wiring problems you would typically encounter, and this versatile handset makes finding those wiring problems a whole lot less aggravating.

For more information about T3 Innovation or other products, click here to go to Utility Products Buyers Guide.

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