Distance To Fault

Distance To Fault dialog

The following settings are used to perform a Inverse Fast Fourier Transform (IFFT) of the Frequency Domain data. When finished, press OK to generate the DTF plot.

Note: Markers can NOT be added to the resulting Distance to Fault plot.

Distance Settings

An alias fault is not a true device response. An alias fault appears because of the method used to convert frequency to time.

Maximum Unaliased Range  The total (stop - start) distance that could be guaranteed to NOT see an alias response. This range is related to the frequency range of the CAT measurement. For a larger unaliased range, choose a smaller range of measurement frequencies.

Start / Stop Distance  The X-axis distance to show on the plot.

Range and Resolution

Window  Provides the ability to choose between optimizing DTF measurements for resolving closely-spaced faults or for the ability to measure low-level faults. Choose from the following:

• Maximum – Optimized for dynamic range, the noise floor is lowered to provide the ability to measure low-level responses. (Default setting)

• Medium – Compromise between Min and Max window settings.

• Minimum – Best Response Resolution, providing the ability to resolve between two closely-spaced responses.

DTF Units  Choose from Feet or Meters.

Cable Correction  By default, the FieldFox does NOT compensate DTF measurements to account for the inherent loss of a cable. However, to make more accurate DTF measurements, the cable loss and velocity factor can be entered using one of the following methods:

• Auto  Select a Cable Name from a list which contains the cable loss in dB/meter and velocity factor. Several cable files are located on the FieldFox. You can send one or more of these files to the PC Learn how. Then click Browse to navigate to the file on your PC.

• Manual  Enter cable loss and velocity factor for the DTF measurement.

Cable Loss (dB/m) -  Cable loss is directly proportional to the length of the cable and the frequency of the signal that passes through the cable. Only one Loss value can be used for the entire frequency range of the measurement.

Velocity Factor -  Velocity Factor is a property of the physical material of a cable. A VF of 1.0 corresponds to the speed of light in a vacuum, or the fastest VF possible. A polyethylene dielectric cable has VF = 0.66 and a cable with Teflon dielectric has VF = 0.7.

27-Sep-2011

Added Markers note