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DTX-1500 CableAnalyzer
Technical Reference Handbook
HDTDR Analyzer
The HDTDR
(High-Definition Time Domain Reflectometry)
analyzer plots the locations and magnitudes of reflections
caused by impedance anomalies. See page 6-22.
Resistance
Resistance results show the dc loop resistance for the center
conductor and shield. The smart remote shorts the
conductor and shield to create the loop.
Most standards do not have a limit for resistance. The tester
shows an
when no limit is available.
Tip: The resistance test in Single Test mode features a
scanning function that runs the resistance test
continuously. This function is helpful for locating
intermittent faults.
Impedance
Impedance measurements require a cable at least
13 ft (4 m) long. The tester shows Unknown for
cables shorter than this.
Impedance results show the approximate characteristic
impedance of the cable at a point approximately 13 ft
(4 m) from the tester.
5-10
Note
Characteristic impedance is the impedance a cable would
have if the cable were infinitely long. Good cabling has
relatively constant characteristic impedance throughout the
cable and connectors.
Changes in impedance cause signal reflections in cabling. In
computer networks, signal reflections can cause network
faults. In video systems, reflections can cause poor
reception.
Length
Length results show the length of the cabling.
Differences between measured and actual length
values can be caused by variations in the cable's
NVP value. NVP values can vary among cable types,
lots, and manufacturers. In most cases, these
differences are minor and may be disregarded.
Propagation Delay
Propagation delay is the time taken for a test pulse to travel
the length of the cabling. The delay is measured in
nanoseconds. One nanosecond is one-billionth of a second,
or 0.000000001 second.
Note
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