Ideal Networks PoE Pro Guía De Uso página 12

Length Measurement
Cable length can be measured using the
built-in Time Domain Reflectometer (TDR)
with either an open circuit or short circuit
or a Remote Unit or Identifier at the far end.
EN
Any TDR can only be used to measure the
length of cables with uniform Characteristic
Impedance. The TDR may not give reliable
results on cables that are not correctly
twisted or using crocodile clips to connect to
the cable.
Accurate length measurement relies on correct setting of the Nominal Velocity of Propagation
(NVP) for the cable to be tested. This can be determined either from the cable manufacturer's
data or by testing a known length of cable of the same type as the cable to be tested.
To set the NVP:
• Connect a known length (>15m / 50ft) of
cable to the tester (if available).
• Press the TOOLS button repeatedly until
the NVP setting flashes.
• Press or
or the known cable length is displayed.
• Press the TOOLS button repeatedly until
the Setting Indicator disappears.
Overall Cable
Length
NVP
Setting
12
until either the required NVP
Length Units
Length can be shown in units of either meters
or feet.
To set the length measurement units:
• Press the TOOLS button repeatedly until
either the m or ft symbol flashes.
• Press or
o The length units change between meters
and feet.
• Press the TOOLS button repeatedly until
the Setting Indicator disappears.
To measure the cable length:
Connect the cable to the tester.
• The display shows the cable length.
Press the port selection button of the
currently selected port.
• The display changes to show the overall
cable length or the length of an individual
pair inside the cable.
Repeat to show the length of each pair or the
overall length in turn.
• By investigating the individual pair lengths,
cable faults and distance to fault can be
found.
• The individual pairs are often different lengths
and may be longer than the overall cable
because of the internal twisted construction.
Length of Pair 1-2
PoE PRO
Length of Pair 3-6
158823.01