The length of the link has been exceeded, but the analyzer still passes it | Fluke Networks

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The length of the link has been exceeded, but the analyzer still passes it

If you have selected a TIA Standard, the length test will not fail until the prescribed length plus ten percent has been exceeded.
 
If you are measuring a Permanent Link which has a limit of 90 meters, the length test will not fail unless the measured length is greater than 99 meters (90 meters + 10%).
 
From the cabling standard ANSI/TIA/EIA 568-B.1
11.2.4.3.1 Physical length vs. electrical length The Pass or Fail criteria is based on the maximum length allowed for the channel or permanent link given in figures 11-1 and 11-2 plus the NVP uncertainty of 10%. 
  
If you have selected an ISO or EN Standard, length is not required for compliance. You cannot therefore fail on length,
 
The active equipment is not concerned about the physical length, only that the attenuation, propagation delay and delay skew are within specification. This is why length is not a requirement in ISO/IEC 11801:2002
 
From the cabling standard ISO/IEC 11801:2002

 
 
In Table B.1 above, the type of test to be carried out for each channel or permanent link is indicated by an "I" (informative) or "N" (normative). Parameters, which are computed from the measured parameters, are indicated by a "C". The tests indicated by I may be carried out as part of an acceptance test. The tests indicated by N shall be carried out as part of an acceptance, reference or compliance test.

 

Author: Adrian Young

Creation Date: 2014-02-17

Last Modified: 2014-02-17