What is the difference between a tester, a qualifier, and a certifier?

A tester checks continuity and wire map — it tells you the eight conductors reach the right pins. A qualifier adds a judgement about whether a given speed will run. Only a certifier measures the frequency-domain parameters against a TIA or ISO limit line and produces a report that satisfies a manufacturer warranty. If somebody asked for certification, the first two do not answer the question.

What does a PASS with an asterisk mean?

The result is within the accuracy tolerance of the instrument at that measurement, so the tester cannot say with confidence that it passed — it is marginal. It is a legitimate result to record but not one to hand over silently. Treat it as a re-termination candidate, because a marginal link is the one that fails when the room warms up.

NEXT failed. Is the cable bad?

Almost never. Near-end crosstalk failures are overwhelmingly a termination problem, and the specific cause is untwist — pairs opened up further than they should be at the jack or panel. Re-terminate both ends keeping the untwist under half an inch before you consider pulling the run.

Insertion loss failed. What now?

This one usually is the cable or the length. Check the measured length against the limit first — a run over 90 metres of horizontal cable will not pass regardless of workmanship. If length is fine, look at whether the run is copper-clad aluminium rather than solid copper, and whether it has been through heat.

What is delay skew and why does it matter?

Different pairs in the same jacket can have slightly different physical lengths and propagation speeds, so bits sent together arrive apart. Gigabit and above use all four pairs simultaneously and reassemble them, so too much skew breaks the link. Large skew usually means the pairs are made of different materials, which points at cheap cable.

Do I test the permanent link or the channel?

Permanent link for a new installation you are warranting — outlet to patch panel, excluding patch cords, because that is the part you installed and the part that stays. Channel when you are diagnosing what a device actually experiences, cords included. Reporting one when the specification asked for the other is the most common reason results get rejected.

Field guide · Testing & verification

Reading a Cable Certifier Report

A certification report is a compliance document. A pass sticker is not the same thing and will not survive an audit. This explains what each measurement is telling you — wire map, length, insertion loss, NEXT, PSNEXT, ACR-F, return loss and delay skew — which failures point at the termination rather than the cable, and why an asterisk beside PASS is not something to hand over quietly.

Diagram

What PASS* actually means, and which number to look at first.

Result

Almost always the terminations, not the cable.

Permanent linkFAIL

ParameterResultMargin

Wire mapCorrect—

Length48 m42 m

Insertion loss18.2 dB6.1 dB

NEXT32.1 dB−2.4 dB

Return loss12.8 dB1.9 dB

Delay skew18 ns32 ns

Margin is headroom against the limit. Negative is a fail; an asterisk means the value is inside the tester’s own accuracy tolerance.

What it means

Near-end crosstalk is failing while length and insertion loss are comfortable. Crosstalk is created where the pairs are opened up — at the jack and at the panel — not along the run.

What to do

Re-terminate both ends, keeping the untwist under half an inch. Do not pull the cable until you have done that; the run itself is almost certainly fine.

Fig. 01Three results: the failure that is workmanship, the failure that is not, and the pass nobody should hand over quietly. Margin is the column to read.

Questions

Questions people actually ask

What is the difference between a tester, a qualifier, and a certifier?: A tester checks continuity and wire map — it tells you the eight conductors reach the right pins. A qualifier adds a judgement about whether a given speed will run. Only a certifier measures the frequency-domain parameters against a TIA or ISO limit line and produces a report that satisfies a manufacturer warranty. If somebody asked for certification, the first two do not answer the question.
What does a PASS with an asterisk mean?: The result is within the accuracy tolerance of the instrument at that measurement, so the tester cannot say with confidence that it passed — it is marginal. It is a legitimate result to record but not one to hand over silently. Treat it as a re-termination candidate, because a marginal link is the one that fails when the room warms up.
NEXT failed. Is the cable bad?: Almost never. Near-end crosstalk failures are overwhelmingly a termination problem, and the specific cause is untwist — pairs opened up further than they should be at the jack or panel. Re-terminate both ends keeping the untwist under half an inch before you consider pulling the run.
Insertion loss failed. What now?: This one usually is the cable or the length. Check the measured length against the limit first — a run over 90 metres of horizontal cable will not pass regardless of workmanship. If length is fine, look at whether the run is copper-clad aluminium rather than solid copper, and whether it has been through heat.
What is delay skew and why does it matter?: Different pairs in the same jacket can have slightly different physical lengths and propagation speeds, so bits sent together arrive apart. Gigabit and above use all four pairs simultaneously and reassemble them, so too much skew breaks the link. Large skew usually means the pairs are made of different materials, which points at cheap cable.
Do I test the permanent link or the channel?: Permanent link for a new installation you are warranting — outlet to patch panel, excluding patch cords, because that is the part you installed and the part that stays. Channel when you are diagnosing what a device actually experiences, cords included. Reporting one when the specification asked for the other is the most common reason results get rejected.

Other guides

Related guides

Book the work

We do this work
as well as document it

Anyone handed a set of results to sign off, or holding a failure and trying to work out whether to re-terminate or re-pull.

Get a free estimate Low-Voltage & Cable Management

Or call and speak to someone who does the work(347) 262-9435 inquiries@jcitsystems.com

Free guides
No sign-up
Nothing tracked
Written on the job

Reading a Cable Certifier Report

What PASS* actually means, and which number to look at first.

Questions people actually ask

Related guides

Toning and Tracing a Cable

Which Cable Tester Do You Need?

RJ45 Wiring: T568A and T568B

RJ11 Wiring and Phone Pinouts

Keystone Jack Termination

66 Block Wiring

We do this work
as well as document it