16
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.
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