IDEAL INDUSTRIES FIBERTEK, Руководство пользователя

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Chapter 3
Structured Cable Field Calibration and Testing
3-37
VIEWING TDR RESULTS
When the TDR diagnostic function is first started, the graphical plot is automatically
scaled to the full length of the cable. A maximum of 2000 feet (609.6 meters) of cable
results can be displayed on a TDR graph.
When TDR is first activated, the left 10% of the graph displays prelaunch impedance
signal rise distance data and the right 10% of the graph displays reflection data.
¾
Press the LEFT/RIGHT ARROW keys to move the cursor horizontally. As the
cursor moves, screen data displays will change to reflect cursor position.
¾
Press the UP/DOWN ARROW keys to view TDR results from a different wire
pair. The TDR test runs one time and displays the results.
¾
Press the ZOOM keys to scale the graph. At the maximum or minimum limits
the key becomes inactive.
¾
TDR results can be uploaded and saved to a PC and printed.
INTERPRETING TDR RESULTS
Always note the cable pair currently being displayed. The shape of the reflections
plotted for the pair can be used to identify and locate problems. If the cable pair has
no problems along the entire length of the pair, the graph will appear as follows:
¾
The graph has an upswing point on the left most 10% of the display (start of the
cable).
¾
The following 80% of the graph is relatively flat.
¾ The graph has an upswing or downswing point on the right most 10% of the
graph (end of the cable).
At the end of the cable (right-side), a slope to the top means the pair is open, while a
slope to the bottom of the screen indicates that the pair is shorted.
EVALUATING A TDR GRAPH
When evaluating the TDR graph, the first consideration should be the average
impedance of the cable being tested:
¾ A graph with sharp dips or spikes can identify anomalies.
¾ For subtle problems, interpretations should be based on benchmark data
obtained from the analysis of many cable segments.
When anomalies are detected in the cable pair, the cursor is automatically placed on
the first anomaly. Press the ARROW keys to highlight the anomaly of interest.
Impedance and distance values will be displayed on the screen.
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