Autotest
Link Performance Grade Result (Headroom)
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Link Performance Grade Result (Headroom)
When an Autotest is complete, the display shows the overall result (pass or fail)
and the headroom value. Headroom may be taken from NEXT, ACR, PSNEXT, or
another critical parameter required by the selected standard. Headroom is the
smallest difference found between a measurement and its limit. This number
serves as a figure of merit that reflects the overall performance of the link. Larger
headroom values correspond to better cable performance.
To pass or fail a cable based on a minimum headroom value, enter the minimum
value as part of a custom test standard (see Chapter 6).
Worst Margin and Worst Value Results
Worst margin and worst value results are shown for frequency-dependent tests
such as NEXT, RL, ELFEXT, and ACR. Worst margin results are measurements
that came closest to the limit, or that exceeded the limit by the greatest amount.
Worst value results are the lowest measurements found, which may not necessarily
come closest to the limit.
Worst margin results for attenuation are not required by any test standard and are
not reported.
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