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Fault Mapper Model CA7024
CHAPTER 4
OPERATION
4.1
Principles of Operation
The Fault Mapper works by measuring the time taken for a signal to travel
to the far end of the cable under test, or to an intermediate fault and return.
The velocity at which the signal travels, or Velocity of Propagation (Vp),
will depend on the characteristics of the cable.
Based on the selected Vp and the measured travel time of the test pulse,
the Fault Mapper calculates and displays distance.
4.2
Accuracy and Velocity of Propagation (Vp)
The Fault Mapper measures distances to faults and cable lengths to an
accuracy of ±2%.
This measurement accuracy is based upon the correct value of Vp being
used for the cable under test, and homogeneity of the Vp along the cable
length.
If the Vp is set incorrectly by the operator, or the Vp varies along the length
of the cable, then additional errors will be incurred and the measurement
accuracy will be affected.
See § 4.9 for setting the Vp.
NOTE:
The Vp is less well defined with unshielded multi-conductor
cable, including power cable, and is lower when a cable is tightly
wound on a drum than when it is installed in a linear fashion.
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