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Velocity Factor

The velocity factor is used by the instrument to convert the measured time for a pulse to be reflected, into a distance. It is

displayed as a ratio of the speed of light (eg 0.66 = 66% of the speed of light).

If the exact length of cable is known and the reflection from the cable end is visible then an accurate velocity factor can be

determined:

Locate the reflection caused by the end of the known length of cable with the instrument set on the shortest possible

range to see the end of the cable.

Locate the start of this reflection as described in the Operation section of this manual.

Adjust the velocity factor until the correct cable length is shown.

Note the VF value for future reference.

The measurement of the distance to the fault can now be made with more confidence. The ability of the instrument to accurately

measure the distance to a cable feature relies on the velocity factor being correct. Any errors in the velocity factor are directly

related to distance measurement errors.

Содержание Megger CFL510G

Страница 1: ...Page 1 of 1 M TDR1000 3 TDR1000 3P CFL510G TDR500 3 Time Domain Reflectometers User Manual ...

Страница 2: ... General testing procedure 13 Operating modes 13 Connection to cable under test 14 Velocity factor 16 Pulse widths 17 Techniques 18 Test the cable from both ends 18 Care and maintenance 18 Battery 19 Battery replacement 19 Battery indicator 20 Specifications 21 Waste electrical and electronic equipment 23 Test Lead selection 25 Repair and warranty 26 Megger contact information ...

Страница 3: ...y the correct lead set The operator must verify that the circuit is safe before testing and take the appropriate precautions Ensure that hands remain behind guards of probes clips when testing The instrument should not be used if any part of it is damaged Also all test leads probes and crocodile clips must be in good order clean and with no broken or cracked insulation Disconnect the test leads be...

Страница 4: ...UTION RISK OF DANGER t EQUIPMENT PROTECTED THROUGHOUT BY DOUBLE INSULATION OR REINFORCED INSULATION c EQUIPMENT COMPLIES WITH RELEVANT EU DIRECTIVES EQUIPMENT COMPLIES WITH AUSTRALIAN EMC REQUIREMENTS C tick NOT FOR SAFETY THIS EQUIPMENT SHOULD BE RECYCLED AS ELECTRONIC WASTE ...

Страница 5: ...dance will cause a reflection of the same polarity i e positive while faults with impedance lower than that of the cable will cause a negative going reflection Matched cable terminations absorb all the pulse hence no end of cable reflection will occur the cable appearing endless Open or short circuits will reflect all the pulse and a large reflection will be displayed At an open or short circuit a...

Страница 6: ...der test maximum power can be transmitted into the cable allowing long cables to be tested If the impedance of the cable under test is unknown the auto impedance function may be used to determine the cable impedance and set up the TDR automatically The distance units can be changed between metres and feet Display contrast is automatically adjusted for temperature but can be adjusted further for op...

Страница 7: ...ntrols range and cursor Rotary Switch Turn to OFF to switch the instrument off Turn to any other position to turn the instrument on Backlight Backlit 256 x 128 dot matrix display Left Right Arrows used in setup There is an audible tone on key presses A low tone means the key is invalid ...

Страница 8: ...Page 8 of 8 Display Range Velocity Factor Impedance Battery State Indication Distance Between Cursor 1 2 Cursor 2 Cursor 1 Position Cursor 2 Position Cursor 1 Hold Indicator ...

Страница 9: ...other position to turn the instrument on The instrument may be turned off by switching to OFF or the instrument may switch itself off if it has not been used for 5 minutes or the battery is exhausted The other selections are Auto Setup Cursor 2 Cursor 1 where fitted ...

Страница 10: ...ge 10 of 10 Range Cursor Control The range is set using the four way switch press up to increase the range and down to reduce the range Moving the four way switch left or right will move the active cursor ...

Страница 11: ...te with no key press when activated or it may be switched off by pressing the key again Hold key When the rotary switch is set to cursor 1 cursor 2 or Auto pressing the hold key will place an image of the current trace in grey on the display This allows comparisons to be made between two cables or intermittent faults to be seen ...

Страница 12: ...the distance to be accurate Refer to the section in this user guide for further information Impedance The impedance is a characteristic of the cable under test and needs to be set correctly for the best display Refer to the section in this user guide for further information Pulse Width The pulse width may be adjusted for a clearer display Gain The gain may be adjusted for a clearer display Distanc...

Страница 13: ...s to the preferred settings Use the setup mode to set the velocity factor and impedance of the cable about to be tested Refer to Velocity factor later in this text for details Operating Modes Auto Impedance of cable under test pulse width and gain automatically selected for chosen range Cable must be greater than 10m or 30 ft 2 Adjust the position of Cursor 2 Manual adjustment of measurement range...

Страница 14: ...round less than 150 V with an installation over voltage category of I V or lower This means that the instrument may be connected to any to primary supply circuits such as overhead cables The voltage must be less than 300 V between the terminals and 150 V CAT IV to earth The fused lead set must be used to connect to power systems Refer to the accessories section ...

Страница 15: ...r end of the cable to ensure that you are seeing the whole length of the cable The range may be changed by moving the four way switch up and down and the cursor moved using the LEFT and RIGHT joy switch Move the cursor to the beginning of the reflection The distance to the fault can then be directly read from the display The distance calculation is performed using the velocity factor set in the TD...

Страница 16: ...end of the known length of cable with the instrument set on the shortest possible range to see the end of the cable Locate the start of this reflection as described in the Operation section of this manual Adjust the velocity factor until the correct cable length is shown Note the VF value for future reference The measurement of the distance to the fault can now be made with more confidence The abi...

Страница 17: ...e distance to fault is not affected by the length of the pulse However if two or more features exist close together excluding open or short circuits then the second or subsequent feature may be partially masked by the reflection from the first fault Hence for potential multiple features the instrument should be used with the shortest suitable range and also the smallest pulse width selected that a...

Страница 18: ... true end of the cable is visible on the display the reflections after the fault may be too obscure to analyze clearly In this case measurement from both ends yields a clearer picture as well as improved accuracy It is also good practice to follow the cable route with a cable tracer as not all cable runs will be straight It can save a great deal of time if the exact route of the cable is known as ...

Страница 19: ...base For battery replacement a Remove old batteries b Refit new batteries following correct polarity as marked on the battery holder c Replace the battery cover d Tighten Screws e Do not mix old and new batteries Incorrect battery cell polarity can cause electrolyte leakage resulting in damage to the instrument 1 Disconnect Leads 2 Undo Screws x 2 3 Lift off battery cover ...

Страница 20: ...at the end of their life Alkaline and NiMH batteries are classified as portable batteries and must be disposed of in accordance with local regulations For details contact your local distributor Battery Indicator The battery state indicates how much life remains in the battery the more black bars are shown the longer the life remaining Replace the battery when there are no bars showing ...

Страница 21: ...onditional on the velocity factor being correct Resolution 1 of range Output pulse 5 volts nominal peak to peak into open circuit Pulse widths determined by range and cable Gain Set for each range with three user selectable steps in Manual operating mode Velocity Factor Variable from 0 2 to 0 99 in steps of 0 01 Power Down Automatic after 5 minutes with no key press Backlight Stays on for 1 minute...

Страница 22: ... EMC Complies with Electromagnetic Compatibility Specifications Light industrial BS EN 61326 1 with a minimum performance of B for all immunity tests Mechanical The instrument is designed for use indoors or outdoors and is rated to IP54 Case dimensions 230 mm 9 in x 115 mm 4 5 in x 48 mm 2 in Instrument weight 0 6 kg 1 32 lbs Case material ABS Connectors Two 4 mm safety terminals Display 256 x 128...

Страница 23: ...ducts is a reminder not to dispose of the product at the end of its life with general waste Megger is registered in the UK as a producer of electrical and electronic equipment The Registration Number is WEE HE0146QT Megger is registered in the UK as a producer of batteries The Registration Number is BPRN00142 ...

Страница 24: ...me Domain Reflectometer includes fused test lead set 1001 789 CFL510G Time Domain Reflectometer includes Bed of Nails test lead set and BNC adapter 1001 790 Accessories User information CD 2002 178 Hard carry case 5410 420 Miniature clip test lead set 6231 652 Bed of nails test lead set 6231 653 Fused test lead set 1002 015 BNC adapter 25965 154 ...

Страница 25: ...Page 25 of 25 Test Lead selection Fused test lead set Megger Part Number 1001 717 must be used on power systems Other test leads and the BNC adapter must only be used on low voltage systems ...

Страница 26: ...ined and qualified personnel The protection is likely to be impaired if for example it shows visible damage fails to perform the intended measurements has been subjected to prolonged storage under unfavourable conditions or has been subjected to severe transport stresses FOR INSTRUMENT WARRANTY DETAILS PLEASE REFER TO WARRANTY CARD SUPPLIED WITH INSTRUMENT Note Any unauthorized prior repair or adj...

Страница 27: ...ibration and repair facilities ensuring your instrument continues to provide the high standard of performance and workmanship you expect These facilities are complemented by a worldwide network of approved repair and calibration companies to offer excellent in service care for your Megger products Approved Service Centres A list of Approved Service Centres may be obtained from the UK address above...

Страница 28: ...eturn e g calibration required or repair Details of the fault if the instrument is to be repaired 2 Make a note of the RA number A returns label can be emailed or faxed to you if you wish 3 Pack the instrument carefully to prevent damage in transit 4 Ensure the returns label is attached or that the RA number is clearly marked on the outside of the package and on any correspondence before sending t...

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