OBJECTIVES 1. Explain the benefits of certifying cable installations. 2. Differentiate between a channel and a basic link. 3. Identify standard tests.

OBJECTIVESOBJECTIVES

1. Explain the benefits of certifying cable installations.2. Differentiate between a channel and a basic link.3. Identify standard tests that should be performed on CAT5 cable runs to certify them.4. Describe the functions typically associated with cable testing instruments.5. Describe the steps associated with testing and certifying basic links and channels.

Figure 6-1: Basic Link and Channel Lengths

Table 6-1: Maximum Horizontal Cable Lengths

Table 6-2: Workmanship’s Impact on Channel Performance

the Wire Map test

TIA/EIA specifications, as outlined in TSB 67, require that four different tests be performed on CAT5 runs immediately after the cable is pulled, and terminated, in order to meet the certification guidelines and to avoid having to troubleshoot certain types of problems later. The four specified tests are:

the Length test

the Attenuation test

the NEXT test

the Power Sum NEXT test

Several additional tests that may be required under certain circumstances include:

the ELFEXT test

the Power Sum ELFEXT test

the Structural Return Loss (SRL) test

the Attenuation-to-Crosstalk Ratio (ACR) test

Figure 6-2: WireScope 155

Table 6-3: Industry Standards Performance Comparison (Worst-Case Channel Performance @ 100 MHz)

* New requirements addressed in TSB95

NEXT test must be performed at both ends of the run.

Simple Rules for Testing:

Documentation of test results must be included.

Cabling/components must not be moved during testing, or retesting will be required.

End-user patch cords must be tested in place. It is suggested that patch cords be 3 meters, but this subject does not as yet fall into the scope of the TIA/EIA T568A standards. It is expected that future releases will deal with this issue.

Figure 6-3: Simple Cable Tester

Before and after installation checkout

The various features for this tester include:

Easy one-step operation

14 LEDs to confirm testing status

Shuts off automatically to maximize power saving

Tests for shorts, connections, non-parallel wiring, and 25/50-ohm BNC terminations

Requires a 9-volt battery

Figure 6-4: Fluke AT5 Tester

Figure 6-5: Wavetek CAT5 Tester

Figure 6-6: Microtest CAT5 Scanner and 2-Way Injector

LAB 16 OBJECTIVELAB 16 OBJECTIVECalibrating and Self-Testing Level II Testers

To understand the procedure for To understand the procedure for properly calibrating the Level II properly calibrating the Level II testers, performing the self test, testers, performing the self test, and documenting the test resultsand documenting the test results

Several warnings are listed in the manual that indicate the possibility of causing the meters to give erroneous test results. Become familiar with these error-causing situations.

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Figure 6-7: Locating the Special Functions Menu

Figure 6-8: Self Calibration Ready

Figure 6-9: Connecting the Calibration Cable

After a slight delay, during which time the control unit reports that the self-calibration procedure is in progress (and various clicks and beeps can be heard), the control unit will display the “SELF CALIBRATION COMPLETE” message.

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Figure 6-10: Message Display in the Control Unit

The screen menu returns to the SPECIAL FUNCTIONS display. Always remember to calibrate the Level II testers before using them.

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The Self Test function of the Level II testers is used to check the operation of both the control unit and the remote unit. It’s a good idea to run this test periodically, as well.

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Figure 6-11: Self Test Ready

After a slight delay, during which time the control unit reports that the self-test procedure is in progress (and various clicks and beeps can be heard), the control unit will display the “SELF TEST PASS” message.

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Figure 6-12: Display Screen for SELF TEST PASS

While the control unit is still displaying the SPECIAL FUNCTIONS screen, it would be a good idea to check the Battery Status function. Because the control unit was charged just prior to performing this procedure, it should indicate that fact during a check.

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Figure 6-13: Display Screen for BATTERY STATUS

If the status of the battery ever drops to a value such that the Level II testers would not operate properly, there will be a specific warning message displayed on the screen.

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Figure 6-14: Changing the Display to ReadNVP = 50%

Figure 6-15: Cable NVP Test Results Screen

Figure 6-16: Cable Length Test Results Screen

Figure 6-17: Changing the Display to ReadNVP = 99.9%

LAB 16 QUESTIONSLAB 16 QUESTIONS

When should the various cables be plugged into the Level II testers?

11


How long should the Level II testers be charged, according to the users manual?

22


What three measurements are taken during a self test between the control unit and the remote unit?

33


When plugging a cable into the Level II testers, which unit (control or remote) should be connected first?

44


How long is the cable that is used to calibrate the Level II testers?

55


Under what circumstances should the Level II testers be calibrated?

66


How long does the self-calibration test take to complete?

77

LAB 17 OBJECTIVELAB 17 OBJECTIVESetting Up Level II Testers

To understand the procedure for To understand the procedure for properly setting up the Level II properly setting up the Level II testers, and documenting the resultstesters, and documenting the results

Not all of the adjustable parameters displayed need to be tinkered with. Once some settings have been selected, they can normally be ignored from then on. Settings that may require periodic changes involve the particular test standard to be run and the type of cable to be tested.

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Figure 6-18: Page 1 of SETUP Menu

Notice that the very first parameter displayed is the TEST STANDARD, CABLE TYPE, because it is the parameter that most often needs to be adjusted.

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Notice that the bottom of the display indicates which of the four numbered buttons to press for the desired screen. You should now see the SELECT TEST STANDARD screen.

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You should now be looking at the SELECT CABLE TYPE screen.

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The control unit returns to the Page 1 display with the selections you just made highlighted. Any tests conducted at this point would expect to see CAT5 100-ohm UTP cable connected to the Level II testers.

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This parameter allows the user to edit the identification information that will appear in any reports that are generated by the Level II tester.

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Figure 6-19: Edit Screen for REPORT IDENTIFICATION

Report identification parameters that can be edited include the CUSTOM HEADER, the OPERATOR, and the testing SITE. Normally, there will be some existing text that was input from another technician or student.

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An alphanumeric listing appears, along with an edit box for the CUSTOM HEADER, containing the previously input text. In order to input the desired text in the editing box, you can use the arrow keys to select a character from the alphanumeric display. Then, use the direction arrow button (1) to select where the character will appear and press the ENTER key. Alternately, you can select an existing character position, and use the INC or DEC buttons to move up or down the alphanumeric list to the desired character. The Delete button (4) will delete the character immediately to the left of the cursor.

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Figure 6-20: Edit Screen for CUSTOM HEADER

The control unit returns to the REPORT IDENTIFICATION screen.

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If you receive any message regarding the fact that the selected parameter has been used to generate a report, and you don’t wish to delete the existing information, simply press the NEW button (2) to add another line of text.

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This means that there are no temperature-dependent limits that would affect the attenuation parameters using this cable. If temperature was an important factor in the use of the selected cable, you could use the CHOICE button (1) to select an average cable temperature that accurately reflected the actual conditions under which this cable was required to operate. Notice that if you press the CHOICE button (1) at this time, nothing happens!

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Figure 6-21: Edit Screen for REMOTE END TESTING

This setting enables you to use the remote unit to measure NEXT and ACR parameters from the far end of the cable under test, provided the test standard selected requires them. Keep in mind that the only time the remote unit is used is when testing twisted pair cable.

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Figure 6-22: Screen for Page 2 of SETUP

Normally, when the Level II testers are used in the field, the results of the various tests that are conducted need to be recorded, and printed, in order to provide the customer and the installer with copies.

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Figure 6-23: Edit Screen for BACKLIGHT TIME-OUT

This screen enables you to specify how long the control unit will allow the backlight to operate before shutting it off. Unless you were a cable installer doing work in a dark wiring closet, there would be no reason to operate the backlight during normal daylight. To conserve the charged batteries, make sure the setting shows 1 Minute. This will turn the backlight off after the control unit detects 1 minute of inactivity. Better yet, conserve even more power by not pressing the WAKE UP button at all, and keeping the backlight off.

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Figure 6-24: Edit Screen for POWER DOWN TIME-OUT

Again, you have several timing choices displayed. This parameter has to do with powering down the display altogether when the control unit detects inactivity. This is another way that the meter conserves its limited battery power. When the meter shuts down the display, it broadcasts an audible signal. The control unit does not forget where it is when it shuts down. To activate the unit once it shuts down, simply press its ENTER key.

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This measurement allows the monitoring of electrical noise, on lines 3 and 6 (pair 2 for T568A), that may be present on a twisted-pair cable. The control unit samples the voltage on the test pair once each second, and records any noise that exceeds this setting as a hit. For 10baseT purposes, 2 hits within a 10-second time span is interpreted as a failure. The default threshold for the control unit is 270 mV, and can be adjusted in 10m V increments.

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You will see settings for handling the serial printing functions available with the control unit. These include PRINTER TYPE, SERIAL PORT BAUD RATE, and FLOW CONTROL. Unless your instructor is planning on printing out reports for your class activities, do not change these settings. The remaining setting on this page is for the AUDIBLE TONE.

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LENGTH UNITS: Feet (ft)

Using what you have already learned, adjust the following settings, if necessary.

NUMERIC FORMAT: 00.0

LANGUAGE: English

POWER LINE FREQUENCY: 60 Hz


SHIELD TEST: Enable

Using what you have already learned, adjust the following settings, if necessary.

CONFIGURE CUSTOM CABLE: * Custom\ Cable 1 *

MAXIMUM FREQUENCY: 100 MHz

CABLE INSIDE CONDUIT: N/A

The CONFIGURE CUSTOM CABLE setting enables the user to set up the control unit for testing cables that possess other than standard parameters. You may look through the various screens that are used to define a custom cable, but there is no need to make any changes to the information you see.

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When does the audible tone sound on the Level II testers?

11


What type of cable would you use the remote unit to test?

22


What is the primary use of the control unit’s backlight feature?

33


How do you reactivate a control unit that has powered down in order to conserve battery power?

44


Why would it be necessary for the results of the various tests that are conducted by the Level II testers to be recorded and printed?

55

LAB 18 OBJECTIVELAB 18 OBJECTIVEAutotesting Patch Cables on Level II Testers

To understand the procedure for To understand the procedure for autotesting previously created patch autotesting previously created patch cables using the Level II testers, and cables using the Level II testers, and documenting the resultsdocumenting the results

Notice that the information provided for the Autotest functions is divided between those designed for twisted pair cable and those designed for coaxial cables. Although the tests conducted for unshielded and shielded twisted pair are identical, the shielded variety is also tested for continuity along the shield.

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Figure 6-29: Autotest Wiring Diagram for Jack Terminations

Figure 4-29 displays a near minimum configuration. A minimum configuration would consist of only one cable. Keep in mind that the cables could be shown routed through a patch panel, wall plate, or various wiring closets. One thing to realize is that the Level II testers will not run an Autotest on twisted pair cable, unless a remote unit (or control unit operating in SMART REMOTE mode) is connected at one end of the wire run.

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The idea here is to examine the wiring condition of the cable you created in Lab 4. Because the other two cables are known to be good, any problems that occur should be traced to the cable under test.

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The remote unit will emit several audible tones.

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Always check to be sure that there are no BNC cables attached to the control unit when testing twisted pair cabling.

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The control unit will emit several audible tones.

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Depending on the wiring setup and the battery condition of the Level II testers, several things may happen. If for some reason the connection to the remote unit is not detected, or if the remote’s batteries are low, you may receive a continuous Scanning for Remote message, rather than a very short one. In this case the Autotest will not be run until a properly charged remote unit is detected. Or, if a calibration message appears on the control unit’s screen, perform the calibration procedure presented in Lab 16.

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Figure 6-30: Autotest PASS and HEADROOM Report Screen

Figure 6-31: Autotest Test Results Screen

Figure 6-32: Wire Map Test Results Screen

All four pairs of wires are displayed, with the various conditions of each wire depicted. Notice that for UTP cable, the shield wire is displayed as an open. If there are no problems detected, the display will appear as shown in Figure 4-32.

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If the cable under test is shown to have some type of problem, you should describe the problem as accurately as possible on your work sheet, and then continue checking the rest of the test results. Once you have finished checking the test results, ask your instructor about correcting any problems that were discovered with the current cable under test.

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Figure 6-33: Resistance Test Results Screen

A typical reading should be far below the 40-ohm limit. The values shown (around 0.5 ohms per pair) are fine for fairly short cable runs. Long runs will show readings above those values, but should still remain below the limit.

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Figure 6-34: Length Test Results Screen

The length is displayed according to the units you selected during the setup procedure. For longer lengths, a slight difference would be normal between the various pairs. A typical display for length is shown in Figure 4-34. If a measured length exceeds the limit, a warning is displayed.

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Figure 6-35: Propagation Delay Test Results Screen

The delay time (in nanoseconds) is given for each individual pair. In cases where a propagation delay is detected, the display includes the longest delay time detected of all four pairs.

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Figure 6-36: Delay Skew Test Results Screen

An important electrical characteristic of cables with regard to high-speed computer network performance is delay skew. This characteristic involves the movement of electrical signals traveling down a length of a multipair CAT5 cable, and arriving at the far end of the cable at different times, depending upon which twisted pair the signals used. The difference in time taken by these electrical signals between the fastest and slowest wire pairs is the measurement called the delay skew. If a computer system’s operation is dependent on simultaneous arrival of these signals, problems will arise at some point.

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Figure 6-37: Impedance Test Results Screen

The characteristic impedance test will require the testing of a cable of at least 16 feet (5 meters) in length. A shorter length than this will automatically pass the test. If the cable under test exceeds the impedance limit specified by the test, the Result column will display the FAIL message. Any pair meeting the specified limit will be given a PASS result.

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Figure 6-38: NEXT Test Results Screen

This test is concerned with the levels of crosstalk that exist between the various wire pairs on the cable being checked. The measurement itself is expressed as the amplitude difference between the test signal and the signal being detected on another pair. The first wire pair listed is the pair into which the test signal is being injected, while the second wire pair listed is the pair from which the crosstalk is being measured. The measurement takes place at the end of the cable attached to the control unit.

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Figure 6-39: Detailed NEXT Test Results Screen

The specific parameters reported for the selected pair include:

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Pairs – The specific pairs for which the displayed data is relevant.

Result – The final determination as to whether the tested wire pairs meet the NEXT requirements for the selected test standard. If the result shown is PASS, then the NEXT between the tested pairs is higher than the standard specifications. A result that reports a FAIL indicates that the NEXT is lower than the standard.

The specific parameters reported for the selected pair include: (continued)

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NEXT – The NEXT value that is considered to be the worst-case measurement, or the value nearest to failure. If the value displayed does fall below the specification, it will be the one that is the farthest below.

Frequency – The frequency at which the worst-case NEXT value is measured.

Limit – For the worst-case frequency, the lowest acceptable NEXT value.


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Margin – The difference between the limit and the measured NEXT value. If the measured NEXT value is higher than the limit, the number will be positive. If the measured NEXT is lower than the limit, the number will be negative.

Recall that the NEXT @ REMOTE measurements are taken from the far end of the cable, and are sent to the control unit by the remote.

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These test results are similar to the NEXT data except that the measurements are taken from the remote cable end.

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Figure 6-40: Attenuation Test Results Screen

The screen shown in Figure 4-40 provides a basic PASS or FAIL report for each pair. The test for attenuation is concerned primarily with how much signal strength is lost over the length of the cable. It is important to use the correct conduit or temperature settings for this measurement in order to avoid getting erroneous results. These settings were initially considered in Lab 17. If they need to be changed, they can be reached from the SETUP menu.

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Figure 6-41: Detailed Attenuation Test Results Screen


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Pairs – The specific pairs for which the displayed data is relevant.

Result – The final determination as to whether the tested wire pairs meet the Attenuation requirements for the selected test standard. If the result shown is PASS, then the attenuation for the tested pairs is lower than the standard specifications. A result that reports a FAIL indicates that the attenuation is higher than the standard.


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Attenuation (dB) – The attenuation value considered to be the worst-case percent margin, at its occurring frequency.

Frequency – The frequency at which the worst-case percent margin occurred.

Limit – For the worst-case frequency, the highest acceptable attenuation value.


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Margin – The difference between the limit and the worst-case attenuation. If the measured attenuation value is lower than the limit, the number will be positive. If the measured attenuation is higher than the limit, the number will be negative.

Figure 6-42: ACR Test Results Screen

The screen shown in Figure 4-42 provides a basic PASS or FAIL report for each pair. The Attenuation-to-Crosstalk Ratio (ACR) is the difference between the measured values of NEXT, and the measured values of attenuation, for each wire pair combination. Obviously, the NEXT and attenuation values (in dBs) must already have been obtained before this parameter can be calculated.

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Figure 6-43: Detailed ACR Test Results Screen


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Pairs – The specific wire pairs from which the crosstalk values used to calculate the ACR were taken.

Atten. Pair – The wire pair from which the attenuation values used to calculate the ACR were taken.


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Result – The final determination as to whether the tested wire pairs meet the ACR requirements for the selected test standard. If the result shown is PASS, then the ACR for the tested pairs is higher than the standard specifications. A result that reports a FAIL indicates that the attenuation is lower than the standard.


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ACR (dB) – The ACR value considered to be the worst-case, or closest to exceeding the specifications. If the ACR does exceed specifications, the displayed value is the one that exceeds the specs by the greatest amount.

Frequency – The frequency at which the worst-case ACR was calculated.


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Limit – For the worst-case frequency, the highest acceptable ACR value. The selected test standard defines the limit.

Margin – The difference between the limit and the worst-case ACR. If the worst-case ACR is higher than the limit, the number will be positive. If the worst-case ACR is lower than the limit, the number will be negative.

The control unit can store up to 500 AUTOTEST results. If the results are to be saved, this must be done prior to another AUTOTEST or SINGLE TEST being performed.

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Figure 6-44: Saving AUTOTEST Results Screen

If necessary, read the users manual section entitled “Saving Autotest Results.” Using a number for the ending character(s) for the cable identification name allows the Level II tester to automatically increment the name, provided that the auto increment function has been enabled. This is useful for testing a series of identical cables.

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Two conditions may exist that will require some additional steps at this point. One of these is the situation where saving the AUTOTEST results fills the last remaining memory location in the Level II tester. This will cause a warning message to be displayed, indicating that the memory is full. The other condition is when the Level II tester’s memory is already full. In this situation, any attempt to save additional test results will cause a message to be displayed indicating that additional data cannot be saved. At this point, previously saved test reports must first be deleted to make room for any new ones. Instructions for doing so can be found in the users manual.

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The only difference here is that the cable under test will be wired for the TIA T568B configuration. The wire map should still indicate wire-to-wire continuity.

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The idea here is to examine the wiring condition of the cable you created in Lab 6. Because the other two cables are known to be good, any problems that occur should be traced to the cable under test.

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Figure 6-45: Autotest Wiring Diagram for T568A Plug Terminations

The idea here is to examine the wiring condition of the cable you created in Lab 7. Because the other two cables are known to be good, any problems that occur should be traced to the cable under test. See Figure 4-46, if necessary, and take special note of the wire map test.

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Figure 6-46: Autotest Wiring Diagram for T568B Plug Terminations

The idea here is to examine the wiring condition of the cable you created in Lab 13. Because the cable you connected to its jack end is known to be good, any problems that occur should be traced to the cable under test.

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Figure 6-47: Autotest Wiring Diagram for Jack/Wall Plate Terminations

Consider the RJ45/T568A modular plug to be the far end of the cable.

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The idea here is to examine the wiring condition of the cable you created in Lab 14. Because the cable you connected to its jack end is known to be good, any problems that occur should be traced to the cable under test.

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Figure 6-48: Autotest Wiring Diagram for Jack/Edge-Connector Terminations

Consider the RJ45/T568A modular plug to be the far end of the cable.

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The idea here is to examine the wiring condition of the cable you created in Lab 9. Because this cable has already passed the preliminary continuity checks, any problems that occur will be related to other cable parameters.

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Figure 6-49: Autotest Wiring Diagram for RG58 Network

Figure 4-49 displays a networked configuration connected to the Level II tester, consisting of several computers cabled together (with a terminator attached to the end node). Keep in mind that the cables could be routed through a patch panel, wall plate, or various wiring closets.

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Figure 6-50: Single Section Coax Testing Diagram

Figure 6-51: IEEE 10Base2 Test Standard and RG 58 Cable Type

Figure 6-52: Screen Before IEEE 10Base2 RG 58 Autotest

Never change the settings on the tester to allow a test to pass that would fail at the correct settings.

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Figure 6-53: Autotest Results for IEEE 10Base2 RG 58

Notice that the Resistance test shows a PASS result. If it showed a FAIL result, this would be interpreted as an open circuit. This is because the terminator was removed from the far end of the cable(s) under test.

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Keep in mind that when a cable installation is being made for a customer, it’s important to make a second copy of the documentation to leave at the premises.

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The NO REFLECTION report for the Length parameter indicates a correct terminating resistance. With no signal reflections, the Level II tester cannot measure the cable’s length.

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The idea here is to examine the wiring condition of the cable you created in Lab 11. Because this cable has already passed the preliminary continuity checks, any problems that occur will be related to other cable parameters.

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Figure 6-54: Single Section RG 8 CoaxTesting Diagram

Notice that this diagram is similar to Figure 4-46, except that the N connectors have been outfitted with the RG8 to BNC adapters for use with the control unit and the terminator.

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Figure 6-55: IEEE 10Base5 Test Standard and RG8 Cable Type

Figure 6-56: Screen Before IEEE 10Base5 RG8 Autotest

To do this, first connect the RG8 cable to the N side of one of the RG8 to BNC adapters. Then, connect the BNC side of the adapter to the Level II tester.

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Figure 6-57: Autotest Results for IEEE 10Base5 RG8

Notice that the Resistance test shows a FAIL result, and is interpreted as an open circuit. This is because the terminator was removed from the far end of the cable(s) under test.

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Keep in mind that when a cable installation is being made for a customer, it’s important to make a second copy of the documentation to leave at the premises.

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The NO REFLECTION report for the Length parameter indicates a correct terminating resistance. With no signal reflections, the Level II tester cannot measure the cable’s length.

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From cables you made during previous lab procedures, which, if any, failed their respective test standards on the Level II testers?

11


Of those tests performed during an AUTOTEST, which ones are specified by the TIA/EIA T568A or T568B standards?

22


Which tests performed on twisted pairs required the use of a smart remote unit?

33


On average, how long did the Level II testers take to provide the AUTOTEST results for one of the CAT5 twisted pair cables you tested?

44


What other cable or connector types besides CAT5 UTP RJ45 terminations are the Level II testers capable of testing?

55


What differences, if any, were evident during the various wire map tests using the CAT5 T568A and T568B cables? Explain.

66

Figure 6-58: Basic Link Testing

Figure 6-59: Channel Testing

REVIEW QUESTIONSREVIEW QUESTIONS

What is a channel, as it applies to a horizontal cable run?

11


How is a basic link different from a channel?

22


Why should network cabling be tested to a standard before the network equipment is connected to it?

33


What is the maximum horizontal cable length for a basic link?

44


How are Level I and Level II cable testers different?

55


State the maximum length of patch cords that can be used when testing a basic link.

66


If equipment is repositioned after a certification test has been performed, what action must be taken?

77


What is NEXT?88


What action is required if a run passes a test with the minimum acceptable values?

99


How would wrapping a cable around a 3-inch pipe affect its NEXT performance rating?

1010

OBJECTIVES 1. Explain the benefits of certifying cable installations. 2. Differentiate between a channel and a basic link. 3. Identify standard tests.

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