シールドの整合性試験 - DSX CableAnalyzer

If you have access to YouTube, you can click here to watch a video of this new feature in action.
 
In data centers where the shield is typically grounded at both ends, ANY wire map tester will report the shield as connected, even if it is not. That's because the shield test is a simple DC Resistance measurement. If the shield is open, it will find the remote unit using the building ground (earth).

            

The DSX CableAnalyzer offers a unique solution to this problem. It ties the four pairs together and then sends a differential signal down the cable treating the shield as the second conductor. This allows the DSX CableAnalyzer to view the shield in the time domain. So even if the patch panels are grounded, it will report the shield open, if indeed it is open you would see:
 
                                                                                                              

And since it is using time domain techniques, the distance to the open is given. In this example, we can see the patch panel at the near end is the issue.

The scenario above occurs when the technician grounds the connector on the non conductive side of the cable shield. The result is degraded Alien Crosstalk performance. Since users are told that shielded cabling systems do not need to be tested for Alien Crosstalk, one wonders how wide spread this issue is and whether users are getting the performance they paid for.


補足情報
If you only use the drain wire to connect the shield and that drain wire is greater than approx. 2 inches (5 cm), the DSX CableAnalyzer may report the shield as open. This is by design. Such a termination acts as an open circuit at the frequencies we are talking about here.