CHAPTER 7 Copper Cable Testing

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1 CHAPTER 7 Copper Cable Testing Lesson Objective After completing this lesson, you should be able to: i. Explain the various terms and instruments used to test copper cabling system. Cable Testing Cables can be tested with many different types of testing devices. The most common type of device to perform complete testing is a certification field tester. Certification field testers are the most common testing devices for certifying cabling systems. These testing devices are useful in the identification of improperly installed or terminated communication cables like continuity tester. A certification field tester is a comprehensive testing and certification device. It can perform basic continuity testing, and it can also perform more comprehensive performance testing. A certification field tester is used to certify installed cabling links to ensure that these cabling links will support high speed networks. EC2023PA: Cabling Technology Page1 1

2 Why need to test cable? Cable testing is an organized and systematic process of verifying that communication cables are installed and terminated correctly. Cable testing is performed with cable testing devices to confirm that the installation complies with the projects requirements and industry cabling standards. Cable testing is required to confirm that the installation was performed correctly and that the installed cables will provide reliable operation. Cable testing confirms that current applications will successfully work over the new cable system. It also provides performance specifications that will verify that the cables will support future applications as well. The process of testing communication cables includes: Visual inspection of the cables and the cable termination. Continuity testing Performance testing Wire Map test Attenuation test Visual Inspection The visual testing is the first step in testing a newly installed cabling system. The cabling system must be visually inspected after the installation is completed, to verify that the communication cables are installed in the cable pathways correctly. The cables must be supported properly in the cable pathways. The cables terminations must be visually inspected. The visual inspection must confirm that the cables are terminated in the correct location. It must also confirm that the correct color code was followed and the correct termination technique was used for the installation. Continuity Testing The second phase of testing the cabling system is performing complete continuity testing. Communication cables must have continuity to complete an electrical path for communication signals to flow between communication system devices. Communication cables are usually multi pair cables. Each cable pair is terminated to different pairs of a connecting hardware component to conform to a specific modular outlet configuration. EC2023PA: Cabling Technology Page1 2

3 Continuity testing will check the electrical path from one end of the cable to the other. A continuity test will also check to verify that the wires are terminated in the correct position and in the correct order. Performance Testing The last phase of testing the newly installed cabling is to conduct performance testing on all of the communication cables. Performance testing will determine if the installed communication cables will exhibit low attenuation and low crosstalk resistance. Performance testing will confirm that the correct components and the proper installation techniques were used during the installation. Performance test characterize the installed cable. They provide an indication of whether the installed communication cables provide a reliable transmission path for communication signals. EC2023PA: Cabling Technology Page1 3

4 Wire Map test Security Technology Department Chapter 7 The first requirement for the successful transmission of communication signals over communication cables is end to end continuity of the cable pairs. Correct continuity of the communication cable pairs requires that the pairs are strictly connected across the cable link. This means that the wire connected to pin 1 should be connected to pin 1 on the patch panel in the telecommunications room. Wire Map Open An open is a condition where a single wire or multiple wires do not provide continuity from one end of a link to the other. This condition is normally signified by an O next to a pin on a wire map graphic. EC2023PA: Cabling Technology Page1 4

5 Twisted pair cables should have complete continuity for all eight conductors (four pairs) across the cable link. If an open condition is identified for one wire of a twisted pair cable, check all the connection points for the wire showing open. If all wires of the cable are showing open condition, verify that the correct cable is being tested. Wire Map Short A short is a condition where two or more wires from a cable are connected ahead of where they should normally be connected in the circuit. This condition is normally identified by a line showing more than one pin of the outlet being electrically connected together. Twisted pair horizontal cables should not have any shorts in the cable link. If a short condition is identified by the testing device, check the terminations at the patch panel and work area outlets. Two wires may be terminated in the same termination slot. If the problem cannot be identified in the terminations, visually inspect the horizontal cable and all the patch cables in the link. Your visual inspection may identify that a cable s jacket may be torn or pinched. If this is the case, the damaged cable should be damaged. Wire Map Reversed Pair A reversed pair is a condition where the two wires of a pair are connected to the wrong pins. A reversed pair condition would mean that a signal transmitted on pin 1 would end up on pin 2 on the opposite end of the cable. The cable tester would show two lines crossed. EC2023PA: Cabling Technology Page1 5

6 Wire Map Crossed pair Security Technology Department Chapter 7 A crossed pair is a condition where the wires of a pair are connected to the wrong location on a modular outlet. The tester would show the two lines of a cable pair being terminated on different pins on the opposite end of the link. Attenuation Test Attenuation is defined as the reduction of transmitted signal due to the resistance encountered by the signal as it is traveling down a cable. An attenuation test is a measure of the amount of signal loss in the cable and connecting hardware of a cable link. Attenuation causes signals to shrink as they travel along a cable. Attenuation is measured in decibels (dabs). The dbs rating is specified per unit length of cable (usually 100m). The higher the attenuation db value, the greater the attenuation (signal loss) and the weaker the received signal. When measuring for attenuation, the lower the db values the better. The two primary causes of attenuation on a twisted pair cables are the Length of the cable Frequency of the transmitted signal over the cable Troubleshooting Failed Cables When a communicating cable is tested and the test result is a failure, the cause of the failure must be identified and corrected. Many times the cause of a failure for a cable performance test is the result of using an incorrect quality component. Another common cause of cable test failures is untwisting cable pairs. EC2023PA: Cabling Technology Page1 6

7 The following steps should be followed for troubleshooting communication cables. 1. Determine the exact cabling problem and verify if it is actually cable related. 2. Perform a visual inspection looking for anything unusual. 3. Use the cable testing devices and perform tests. 4. Break the cable segments into smaller parts and test each part. 5. Verify the correct cable and connectors were used. 6. Check for improper installation practices. 7. Replace suspect equipment or work area patch cords. 8. Look out for any damaged cable. 9. Look for any sources of interference close to the cable. 10. Check if there are any excessive cable distances. EC2023PA: Cabling Technology Page1 7