Whole job failing, or passing too well

Likely causes

• Wrong test limit selected

  ~30%

  Every link fails the same parameter by a similar amount, and the report header names a limit that does not match the spec. Real workmanship faults are scattered and inconsistent.

• Wrong test configuration for the deliverable

  ~20%

  Channel length should read longer than permanent link by the cord lengths. If your channel result reads the same length as the permanent link, you are not testing what the header says you are.

• Reference not set, or stale after an adapter change

  ~15%

  Insertion loss and return loss look wrong on every link, sometimes impossibly good at the low end. Set reference and half the job comes back.

• Worn or dirty adapter plug, or a damaged test cord

  ~15%

  NEXT and return loss spike at 0 m on every link. Fit a fresh tip and the spike disappears from all of them at once.

• Wrong NVP or cable type, or a hand-edited custom limit or wiremap

  ~10%

  Reported length disagrees with the as-built or the drum counter by more than about 10%, or the header names a limit or wiremap that is not a standard one. A custom or non-standard wiremap left selected from a previous job will fail correctly wired links right across the board.

• Limit too loose, producing false passes

  ~7%

  Uniformly large margins on a high-category install: a Cat6A job showing Cat5e-style headroom because it was swept to the wrong top frequency. Passes on site, rejected at closeout.

• Firmware and limit library out of date

  ~3%

  The limit the spec calls for is not in the tester's list at all.

What to bring

• Certifier, both units, with permanent link and channel adapters
• Spare adapter tips and test cords
• Certified reference cords
• The spec or RFP page that states the limit
• As-built or drum counter figures
• Laptop or phone for firmware and result management

Steps

1. 1

   Step 1: Read the report header before you read any result

   Limit, test configuration, adapter type, tester and remote serials, reference date, cable type and NVP, and any custom wiremap. One screenshot of that header settles most arguments and finds most whole-job failures.

   If that doesn’t do it

   Header matches the spec exactly: the failures are real. Work them per parameter.

2. 2

   Step 2: Set reference with the exact adapters you are about to use

   Re-reference after any adapter change and inside your tester's stated interval. Check the documentation, it is measured in days, not months. Both units, same firmware.

   If that doesn’t do it

   No change after referencing: move to the hardware.

3. 3

   Step 3: Prove the kit on a link you trust

   Certify a short known-good link. If that fails, the problem is in your hand, not in the building, and you have saved yourself a day.

   If that doesn’t do it

   Known-good link passes clean: the kit is sound and the building has real faults.

4. 4

   Step 4: Fit fresh adapter tips and cords

   Carry spares. Tips are consumables rated for a set number of insertions. Get the figure from your tester's documentation and track it.

   If that doesn’t do it

   Same results with new tips: check the setup numbers.

5. 5

   Step 5: Sanity-check reported length

   Against the as-built or the drum counter. More than roughly 10% out means the wrong cable type or NVP is selected, or there is a stub you don't know about. NVP is on the cable data sheet. Read it rather than accepting the default.

   If that doesn’t do it

   Length agrees: setup is sound.

6. 6

   Step 6: Get the required limit and configuration confirmed in writing

   Before re-testing 400 links. Permanent link and channel are different tests against different limits; so are the TIA and ISO class names for nominally the same cabling.

   If that doesn’t do it

   Spec is ambiguous: test and submit both configurations on a sample and let the consultant pick.

7. 7

   Step 7: Update firmware and the limit library

   Do it in the truck, not on the ladder, and re-reference afterwards.

   If that doesn’t do it

   Limit still missing: contact the tester manufacturer; the deliverable cannot be produced on that build.

More Copper & Certification guides

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• NEXT failing at the panel end
• Split pair, continuity fine, NEXT gone
• Comes up at 100 Mb, not 1 Gb
• PoE device won't power, or reboots under load

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