Fluke 990DSL, Руководство пользователя

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990DSL
Users Guide
4-46
VF Longitudinal Balance Test
This test applies a locally-generated common-mode disturbing tone to the pair,
and simultaneously measures the metallic noise caused
by this tone.
Longitudinal balance is the difference in dB between the two signals.
Setting Up a VF Longitudinal Balance Test
To setup a Longitudinal Balance Test, select the test on the POTS Toolbox and
press
D
(
Setups
). Refer to Table 4-9 for setup parameters.
Table 4-9. VF Longitudinal Balance Setup Parameters
Parameter Setting (default in bold)
Pass Threshold
≥
60 dB (Range = 0 to 80)
Disturbing Frequency 1000 Hz (Range = 200 to 2500)
VF Longitudinal Balance Test Results
To run the VF Long.Balance Test, select it on the POTS Toolbox and press
K
.
Figure 4-28 shows VF Longitudinal Balance test results on a good pair. The
Longitudinal Balance result is shown in the upper right corner of the screen,
along with setup information.
Vg
represents the locally applied disturbing tone, and
Vm
is the resulting
metallic signal due to resistive or capacitive imbalance to Ground.
Longitudinal Balance
(dB) =
Vg
(dBm) –
Vm
(dBm)
Press
A
(
Contin. VF Long. Bal.
) to view continuous test results.