22
Example Traces and Faults
Figures 2-7 and 2-9 (shown earlier) are both examples of an open cable. Whether coax, twisted
pairs, or single-wires in a harness, the trace will go from the cable’s normal impedance straight
upward to maximum impedance reading (>5 x Z
0
) if one or both conductors are open at the
cable’s far end.
Figure 2-11 displays the trace for a 75 Ohm coax cable 60ft feet long and shorted at the end.
The short is indicated by the trace dropping from the cable’s nominal impedance to zero or near
zero Ohms. A twisted pair cable will display the same trace drop to zero or near zero if shorted.
Figure 2-11
Figure 2-12 is an example of a 75 Ohm coax cable with an impedance matched device or
equipment connection. The trace will go on with no end in sight due to the lack of a reflection
from an open or short.
Figure 2-12
Figure 2-13 displays the trace for a 75 Ohm coax cable with an excessive bend or crimp in the
cable at about 17 ft.
Figure 2-13
Summary of Contents for 20TDR
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