Fluke CableAnalyzer DSP-4100, Руководство пользователя

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Basic Cabling Testing
High-Definition Time Domain Reflectometry (HDTDR)
7
7-21
Reflections from Opens
An open, or break, in the cabling represents an abrupt increase in the cabling’s
impedance. The impedance of an open is nearly infinite. In open cabling, a signal’s
energy is not dissipated by a terminating impedance, so the signal bounces back
towards the source. This reflection appears at the source with the same amplitude
and polarity as the original signal, as shown in Figure 7-13. By measuring the
amount of time taken for the reflected pulse to return, the test tool can determine
the location of the open in the cabling.
Transmitted Pulse
Reflected Pulse
End of Fault
Open
Cable
Transmitted Pulse
Reflected Pulse
Short
Transmitted Pulse
No Reflected Pulse
Terminator
(Matches cable
characteristic
impedance)
OFF
PRINT
MONITOR
SETUP
SPECIAL FUNCTIONS
SINGLE
TEST
AUTO TEST
DSP-658
CABLE ANAL
YZER
DSP-601
CABLE ANAL
YZER ADAPTER
TALK
EXIT
ENTER
TEST
SAVE
1
23
4
OFF
PRINT
MONITOR
SETUP
SPECIAL FUNCTIONS
SINGLE
TEST
AUTO TEST
DSP-658
CABLE ANAL
YZER
DSP-601
CABLE ANAL
Y
ZER ADAPTER
TALK
EXIT
ENTER
TEST
SAVE
1
23
4
FAULT
INFO
OFF
PRINT
MONITOR
SETUP
SPECIAL FUNCTIONS
SINGLE
TEST
AUTO TEST
DSP-658
CABLE ANAL
YZER
DSP-601
CABLE ANAL
YZER ADAPTER
TALK
EXIT
ENTER
TEST
SAVE
1
23
4
FAULT
INFO
FAULT
INFO
oy35f.eps
Figure 7-13. Signals Reflected from an Open, Shorted, and Terminated Cable