Fluke CableAnalyzer DSP-4100, Руководство пользователя

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DSP-4000 Series
Users Manual
3-14
NEXT Test
The NEXT test measures the crosstalk between cable pairs at the near end of the
cabling. This crosstalk value is expressed as the difference in amplitude (in dB)
between the test signal and the crosstalk signal. NEXT is measured from both ends
of the cabling over a frequency range defined by the selected test standard.
The first NEXT screen displays the cable pairs tested, the worst-case NEXT
margin, and the test result for each set of pairs.
To see detailed results for the cable pairs, use
D U
to highlight the pairs; then
press
@ View Result
. Table 3-3 describes the items on the NEXT results
screen.
For ISO/IEC 11801-2002 and EN50173:2002 standards, NEXT is not evaluated
where attenuation at the same frequency is less than 4 dB.
Table 3-3. Items on the NEXT Results Screen
Item Description
Pairs
The cable pairs relevant to the results.
Result
The overall result for the NEXT test. A
PASS
result indicates that the NEXT
between the cable pairs was higher than the specified NEXT for the selected
test standard. A
FAIL
result indicates that the NEXT was lower than
specifications.
NEXT
The worst margin and worst NEXT. The worst margin is the NEXT value that is
closest to falling below specifications, or the value that exceeds specifications
by the greatest amount. The worst NEXT is the lowest NEXT value measured.
Frequency
The frequencies where the worst margin and worst NEXT values occurred.
Limit
The lowest NEXT values acceptable for the frequencies above.
Margin
The differences between the NEXT values and the limits. A positive number
means that the measured NEXT value is higher than the limit (PASS). A
negative number means that the NEXT is lower than the limit (FAIL).