Technical data

Chapter 10 279
Distance to Fault
Measuring Distance to Fault
Distance to Fault
Resolution - the Effects of Frequency and Points
It is not always obvious how frequency range affects measured distance and
resolution, and it often appears to be counter-intuitive. If you are new to making
Distance to Fault measurements, this section will help clarify what is happening.
Resolution Distance (in meters) of the DTF measurement, that is, the shortest
distance between two faults that can still be resolved by the analyzer, is determined
by the following equation:
NOTE Please be careful how you interpret this equation. Note that to increase the
resolution, you need to reduce the Resolution Distance; to reduce the resolution, you
need to increase the Resolution Distance.
You can see from this equation that:
•To
increase the resolution, that is, to reduce the Resolution Distance:
— you can
increase the number of points, or
— you can
reduce the measured distance.
•To
reduce the resolution, that is, to increase the Resolution Distance:
— you can
reduce the number of points, or
— you can
increase the measured distance.
NOTE Although you can set your number of points to 256, 512, or 1024, you will only ever
be able to save 256 data points when you save trace data. This is because only 256
points are ever used to display the trace, regardless of how many points you have
used to actually make the measurement. You will not, however, be losing any
resolution, or reducing the quality of your data. The results will still reflect the true
number of data points that you specified.
Automatic and Manual Distance to Fault Measurements
The test set provides two ways of measuring distance to fault:
• Automatic Frequency Range. You select the measurement distance and the test
set automatically selects the
Start Frequency and the Stop Frequency. The
Resolution Distance (in meters)
Measured Distance (in meters)
1
2
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Number of Points×
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