Copper-clad aluminum can pass your channel test and still be a defect — the six incoming checks that catch it, and the wording that makes a supplier answer for it
Ask a cable supplier for pure copper and the invoice will say copper. Ask for the proof and you get a category claim. Copper-clad aluminum is not caught by an attenuation reading — by design, the cladding is thick enough to flatter exactly the tests people run, and thin enough to fail the one number nobody writes on a PO: DC resistance. This page is about that number, about what an aluminum core does at the moment a gold blade pierces it, and about six ways to check a reel at the dock with instruments a connector factory already owns.
Quick answer
- What the specification actually saysCategory cable is required to use solid or stranded copper conductors. Copper-clad aluminum (CCAl), copper-clad steel (CCS) and their cousins cannot legitimately carry a Cat5e/Cat6/Cat6A designation at all — the label itself is the first piece of evidence, which is why CCA turns up on unbranded patch cords and “network cable” rather than on certified reel stock.
- Why it slips past a Fluke testAt 100–500 MHz the skin depth in copper is 6.5–2.9 µm, thinner than a typical clad layer, so attenuation can read acceptable. Direct current does not care about skin depth. A 1.5× resistance multiplier turns a 90 m, 24 AWG loop from 15.2 Ω into 22.7 Ω — over the permanent-link ceiling, with a green data pass.
- Why the plug gets blamedThe aluminum end of the joint creeps, oxidizes instantly, and moves more than copper per degree. A termination that was fine on Tuesday drifts through the first hot-cold cycle. That looks like a bad crimp because the crimp is the only part you can see.
- The cheapest three tests that workMass per 305 m box (a CCAl conductor set is roughly 60 % lighter), a magnet for steel cores, and a four-wire DC resistance on one conductor compared against the computed copper value. Everything else is refinement.
None of this makes a better plug. It makes a smaller warranty argument. Section 8 is the PO wording; section 9 is what to do at the dock on a Tuesday.
- What the specification permits, and the four grades sold as copper
- The skin-effect defense is half right — which is the problem
- The number that decides it: DC resistance, computed
- What aluminum does at a pierced contact
- The same question, applied to the connector
- Six incoming tests, in cost order
- What does not work
- Triage: symptom → is it the conductor? → the one measurement
- Contract language that can be inspected
- The receiving-dock checklist
- What to do with this
- FAQ
- Sources and standards
1. What the specification permits, and the four grades sold as “copper”
The requirement is boring and absolute: balanced twisted-pair category cable is specified with solid or stranded copper conductors. There is no clause that admits aluminum, steel, or a copper wash over either, and no tolerance for “copper-clad” as an equivalent. Confirm the exact wording against the revision you are citing — ANSI/TIA-568.2-D for the permanent link and the ISO/IEC 11801 series on the component side — but the practical consequence has not moved in two decades: a cable with clad conductors is not a category cable, and a data sheet that calls it Cat6 is describing something that does not exist.
What actually circulates is four different things wearing one word.
| Grade | Structure | DC resistance vs copper | What it does at the contact |
|---|---|---|---|
| Bare solid / stranded copper | Cu throughout | 1.00× (baseline) | Wipes clean, gas-tight bite, stable under cycling |
| Copper-clad aluminum (CCAl) | Al core, Cu outer layer, bonded by extrusion | commonly quoted 1.4–1.9× depending on clad fraction | Oxide reforms at the bite, core creeps and cold-flows, thermal cycling loosens it |
| Copper-clad steel (CCS) | Steel wire, Cu flash | several times copper — steel is roughly 6× resistive | Spring-back fights the tine; magnetic, so it is also the easiest one to catch |
| Tinned or brightened alloy sold as “copper” | Brass/bronze or plated steel, tin or Cu-color finish | above copper | Color is not a metal. Common in telephone and cheap patch-cord plugs rather than data plugs |
Where each one appears is predictable. CCAl shows up in fixed-install cable sold by the meter to price-driven integrators, and in finished patch cords where nobody will cut one open. CCS shows up in the cheapest molded patch cords and in RJ11/RJ12 telephone plugs, where the application tolerates junk and the buyer only sees the price. Plated alloy shows up in contact stock — the part sitting in the incoming-inspection bay — and is the one a distributor can screen in thirty seconds with a magnet and a microscope.
2. The skin-effect defense is half right — which is exactly the problem
Every CCA seller eventually produces the same sentence: alternating current travels on the outside of a conductor, so the copper cladding carries the signal and the aluminum core is irrelevant. It is worth taking seriously, because the physics behind it is real. Skin depth in copper is
Skin depth in copper at category frequencies 1 MHz → 65 µm · 100 MHz → 6.5 µm · 250 MHz → 4.1 µm · 500 MHz → 2.9 µm
A clad layer is typically some tens of micrometers thick. So at the upper end of a Cat6 or Cat6A band, the current is sitting mostly in copper. That is why an attenuation reading on a short CCA sample can look unremarkable, and why a seller who has been caught before will honestly believe the cable is fine.
Three things make the argument worthless in practice, and they are the reason a distributor should not accept “it passes the data test” as a defense.
- Power is not AC. Everything carried as DC — PoE, and the whole of 802.3bt on four pairs — sees the full cross-section, skin depth irrelevant. The cladding contributes exactly as much conductance as its own area and resistivity allow, and no more.
- Attenuation is only one of several AC parameters, and it is the forgiving one. The parameters a clad conductor hurts first — return loss from impedance step at the splice of two dissimilar metals, and DC resistance unbalance between pairs — are the ones a marketplace buyer never measures.
- Bond integrity is a construction property, not a frequency property. Extrusion-bonded cladding can be excellent or it can be a sleeve. Under a crimp tine the sleeve is being locally deformed, and a sleeve is not an alloy.
3. The number that decides it: DC resistance, computed
Here is the arithmetic anyone can run, and it beats every clever test on this subject. Resistance of a single conductor is R = ρL/A with the annealed-copper volume resistivity constant ρ = 0.017241 Ω·mm²/m (the ASTM B3 constant). Compute the copper expectation first; measure; compare the ratio.
| Solid conductor | Ø | Cu per 100 m | Cu at 90 m | ×1.5 at 90 m | ×1.68 at 90 m |
|---|---|---|---|---|---|
| 22 AWG | 0.644 mm | 10.59 Ω | 9.53 Ω | 14.30 Ω | 16.02 Ω |
| 23 AWG | 0.573 mm | 13.36 Ω | 12.02 Ω | 18.03 Ω | 20.20 Ω |
| 24 AWG | 0.511 mm | 16.84 Ω | 15.16 Ω | 22.73 Ω | 25.46 Ω |
| 26 AWG | 0.405 mm | 26.78 Ω | 24.10 Ω | 36.15 Ω | 40.49 Ω |
Read the 24 AWG row against the permanent-link DC loop ceiling commonly specified for this class of link — ≤ 21 Ω is the figure most specifications use, and the one to confirm in the revision of TIA-568.2-D actually governing the job. Real copper on a 90 m run costs 15.2 Ω and leaves headroom. The same geometry at a 1.5× multiplier costs 22.7 Ω: the cable has already failed the budget it needs to be able to power a PD, and the data tests are green. The 26 AWG row is the warning for fine-gauge cords — copper alone is already at 24.1 Ω, which is why a 26 or 28 AWG patch cord in a PoE link is a design decision and not a size preference.
Convert the same resistance into heat, because that is what the site actually complains about. On a 90 m, 24 AWG, four-pair Type 4 link at a 52 V PSE, the total current is roughly 1.7 A split across two outgoing and two return pairs, so the effective channel resistance is half of one pair’s loop:
- copper: 7.6 Ω effective → about 23 W lost in the channel
- at ×1.5: 11.4 Ω → about 34 W
- at ×1.68: 12.7 Ω → about 38 W
Call these order-of-magnitude checks rather than compliance verdicts — the split depends on PSE voltage, class and the actual cable — but the scaling is not negotiable: losses move one-for-one with resistance, and a 33 W channel loss is a PD that reboots when the camera heater and the pan-tilt draw together. That is the 3 a.m. ticket, and it is a copper-content problem sitting inside a data connector.
4. What aluminum does at a pierced contact
This section is why a plug manufacturer writes about cable metallurgy at all: every one of these mechanisms happens in the three millimeters of plastic where the connector lives.
Oxide that does not wipe
Copper oxide is soft and partly conductive; the IDC and piercing-contact industry relies on being able to push through it. Aluminum oxide is hard, tenacious and insulating, and it re-forms within moments on fresh metal. The tine’s wipe action that makes a copper joint gas-tight is doing something categorically less reliable on aluminum — and a modular plug carries no anti-oxidant compound, because nothing in the connector industry expects to need one.
Creep and cold flow
Aluminum deforms permanently under sustained load at room temperature. The clamp force on a conductor is a spring doing exactly that, forever. The classic mitigation in building wiring is a torqued lug and a listed bimetallic connector; in an 8P8C plug there is no torque, no disc spring, and no compound. The bite relaxes.
40 % more movement per degree
Expansion coefficients around 23 µm/m·K for aluminum against roughly 17 for copper: about 39 % more travel. Every day-night cycle, every PoE load step, every attic in July is a small fatigue test on a joint that is already held only by elastic interference. Drift, not breakage, is the signature.
A noble cathode the size of a coin
Where moisture reaches a joint between aluminum and a gold- or nickel-finished copper alloy, the electrochemistry is the bad geometry: a large cathode driving a tiny anode. Corrosion current concentrates at the small aluminum area, so the pit forms exactly where the bite is. This is why clad conductors in damp voids drift even when the run is short and the resistance was measured acceptable on day one.
Brittle, and it is not the copper’s fault
Aluminum has lower elongation at break than drawing-grade copper and it work-hardens at the bend. The field pattern is a termination that survives its first crimp, then fails on the second — the re-termination is where crews report the wire snapping inside the plug. Anyone who has been told “your plug cut the wire” about a second attempt should read the next paragraph.
Where the connector takes the blame
A clad or over-hard conductor raises the load needed to seat the tines, and it does not spring back into the window. The visible consequence is a popped pin or a shiny un-insulated sliver — the same symptoms as an under-crimp or a mismatched prong count. The mechanical side is treated in the retention and pop-out article; this is the material that makes the mechanical side fail. Same termination, two ledgers.
5. The same question, applied to the connector
A cable-only diagnosis is half an article. So: what is a contact blade made of, and how would you know? The industry uses phosphor bronze (typically an alloy around C5191) for its elastic range and hardness, beryllium copper where the deflection demands it, brass at the cheap end, and tinned or nickel-silver finishes on request. The rule for a buyer is short: a metal name without a mechanical property is not a specification.
Hardness (HV), 0.2 % proof stress and electrical conductivity are the three numbers that decide whether a blade is still pushing after 750 cycles and ten years of thermal drift. Phosphor bronze is chosen for spring, not for conductivity — it is measurably less conductive than high-conductivity copper, and that trade is the whole point of the alloy. Which makes “pure copper contacts” a claim worth reading twice: pure copper is soft, it creeps under sustained load and its elastic limit is low, so it is an excellent conductor and a poor spring. Where a listing says “pure copper” in the title and “phosphor bronze” in the data table — common across this product category, and not a uniquely foreign habit — the table is the specification and the title is a keyword.
What a credible material statement looks like. Initial contact resistance with its method and test current (a few tens of mΩ is the usual published band for this interface); gold thickness with the measurement technique and the sampling; salt-spray hours to ASTM B117 with a continuity result after exposure; mating cycles with current, rate and acceptance criterion; and for the pin stock, an alloy designation with a hardness range traceable to the coil. A number without a method and a sample count is a marketing figure, whoever printed it.
Two facts about the plug end of the fraud ladder, both cheap to check at a dock:
- Plated steel contacts exist, they are magnetic, and they are the easiest counterfeit to find in a bag of plugs: a rare-earth magnet on a wet sample pulls it out of the box. Bronze, brass, copper and aluminum are all non-magnetic, so a magnet can only catch steel or prove a negative.
- Regrind housing is not a color problem. Recycled polycarbonate loses impact strength and clarity and can turn a crimp into a crack. Where a data table claims 100 % virgin PC and a UL 94 class, the matching evidence is a resin certificate per lot. The field signature is a housing that goes milky after crimping, a load bar with flash lines, or a latch that whitens on its first deflection — and unless somebody asks for the certificate, it gets filed as installer error.
6. Six incoming tests, in cost order
Do them in this order; stop when you have an answer. The first four cost nothing but a balance, a magnet and a multimeter.
| # | Test | How | Verdict rule |
|---|---|---|---|
| 0 | Paperwork | Mill certificate or conductor material declaration naming the alloy and copper conductivity; a category claim is not a material declaration | Refusal to state the base metal = treat as clad and price accordingly |
| 1 | Mass of the reel | Zero the scale, weigh a full 305 m box of conductor only (strip a sample, or use the supplier’s nominal). Computed for 24 AWG solid, 8 conductors, 305 m: about 4.5 kg of copper. Same geometry with a 12 %-by-area clad is about 1.7 kg — roughly 60 % lighter | Conductor mass far below the copper arithmetic, with a stated diameter, is the whole case. Jacket and spline add mass to both, so compare conductor, not gross |
| 2 | Magnet | Rare-earth magnet near stripped conductors and near loose plugs | Pulls = steel core (CCS). No pull proves nothing about aluminum |
| 3 | Four-wire DC resistance | Constant current through one conductor, sense voltage across a measured length; ρ = R·A/L. Compare to 0.0172 Ω·mm²/m | Ratio above about 1.15–1.20 against the copper constant, on a sample measured to the same temperature, is a clad or alloy conductor. This is the test that actually convices a supplier |
| 4 | Cross-section at magnification | Cut, mount, polish, etch lightly; look at 100–200× on a CCD or USB microscope. A bonded clad shows a ring; an alloy shows uniform grain | A visible interface ring = clad. Photograph it — it ends arguments faster than any number |
| 5 | Terminate, pull, cycle | Crimp the suspect cable into a known-good plug, measure per-conductor pull-out, then thermal-cycle and re-measure contact resistance | Drift after cycling with no change in the plug is a conductor problem wearing a connector’s clothes. The method and sample plan are set out in the retention article, section 7.2 |
Two notes on instrument reality. First, test 3 is the one most buyers cannot do today, and it needs one instrument a shop at this end of the industry usually does not own: a 4-wire low-resistance meter, or a 1 A bench supply and a decent DMM with Kelvin clips. It measures in the milliohm-to-ohm range with the current path and the sense path separated, so contact and lead resistance never enter the reading. Second, and important for anyone planning to catch this with the equipment in section 5: a standard XRF plating gauge will not settle a copper-versus-aluminum question. XRF is superb at 3–50 µ” of gold over nickel over copper alloy, and poor at light elements through a metallic overcoat — aluminum reads weakly without a purged or vacuum path, and the cladding you are trying to see is behind the finish you are measuring. Cut the sample and weigh or measure it; do not point a gold gauge at it and call it due diligence.
7. What does not work
Worth stating, because these are what people arrive having already tried.
- The lighter test. CCA strand will burn and discolor where copper will not, and it is a real field trick with a real limitation: it tells you nothing about steel core, it destroys the sample, it does not survive cladding that is thick enough to survive the flame briefly, and no court of procurement accepts it. Use mass and resistance instead.
- Color. Bright, warm, “high-purity looking” copper is a finish. Tin-nickel and copper-flash steel both photograph beautifully.
- Weight of a bag of plugs. Tempting, since density differences are large, but the metal in eight contact blades is hundredths of a gram on a part that weighs roughly 0.8 g. Cable mass is a strong screen; plug mass is noise. On plugs, use the magnet and the cross-section.
- “It passed Fluke, so the cable is fine.” A channel certification is a transmission verdict at one temperature and one moment. It is silent about DC resistance, about oxide behavior at a pierced joint, and about what happens after a summer in a roof void.
- Trust in the label being checked by the party who benefits. Every test in section 6 costs under an hour. If a supplier objects to being asked, that objection is the result.
8. Triage: symptom → is it the conductor? → the one measurement
| Symptom | Also consistent with | Is it the conductor? | Deciding measurement |
|---|---|---|---|
| PD browns out at night or under load | Bundle heat, switch budget, long run | Likely, if the run is long and fine-gauge | Loop DCR at both ends, compared to the section 3 table |
| PoE works on a 3 m test lead, fails on the installed run | Damaged cable, bad termination | Very likely | DCR plus DCR-unbalance pair-to-pair |
| Terminations drift after one season, plug looks perfect | Under-crimp, moisture | Likely if the same cable batch everywhere | Cross-section of a suspect conductor; contact resistance before/after thermal cycle |
| Wire snaps when a crew re-terminates | Over-crimp, wrong die | Likely (work-hardened aluminum core) | Bend test on a stripped strand: copper folds repeatedly, clad/steel cracks |
| Pin pop-out only on one cable lot | Prong/AWG mismatch | Possible | Per-conductor pull force by lot; tine penetration on a cross-section |
| Attenuation and NEXT fine, link intermittent | Shield path, seating | Yes, and this is the classic profile | DCR — because skin effect hid it from the AC tests |
| Cheaper cords on the same job fail more | Everything | Most likely | Mass per box, then resistance. Do not skip the paperwork step |
| Plug contacts rust-colored or magnetic | Storage corrosion | Yes on the magnetic count | Magnet test on loose plugs; ask for the pin stock declaration |
9. Contract language that can be inspected
Two kinds of clause do work here. Put in the pass/fail clauses a receiving inspector can verify on the day, and commission the numeric ones.
9.1 Signable as pass/fail today
| Clause | Write this | Evidence |
|---|---|---|
| Conductor metal | Solid or stranded bare copper per the applicable TIA/ISO category specification; copper-clad aluminum, copper-clad steel and plated-core conductors are a reject, not a deviation | Material declaration naming the base metal and the alloy or conductivity, from the strand producer — not a category claim |
| Conductor geometry | Nominal diameter with tolerance, per AWG, stated on the packing label | Measured micrometer on a sample, recorded against the label |
| DC resistance | Maximum per-unit-length loop resistance at 20 °C stated for the named part number, or: “measured resistivity within 10 % of the annealed-copper constant” | Four-wire measurement on one conductor of a cut sample, at stated temperature, with the instrument named |
| Mass control | Nominal conductor mass per 305 m stated (excluding jacket and spline) | Scale reading on the received lot; a shortfall beyond the stated tolerance is a reject |
| Magnet screen | Conductors and plug contacts shall be non-magnetic unless the order specifically states steel core | Rare-earth magnet on a lot sample, retained as a photographed record |
| Contact base metal | Pin stock named by alloy with hardness and conductivity stated for the supplied coil | Mill certificate traceable to lot; a data table that contradicts the product title is a deviation to be resolved in writing |
| Housing resin | 100 % virgin polymer, UL 94 class as ordered, no regrind | Resin certificate per lot; visual/impact evidence on any lot that crazes or whitens at first deflection |
| Retained samples | Buyer keeps 2 m of jacket and 10 loose plugs per lot for 24 months | Nothing — this clause only preserves your ability to prove the other seven later |
9.2 The ones that need a sample run
| What you ask for | Method | What a real answer looks like |
|---|---|---|
| Conductivity of the finished conductor | 4-wire on a measured length, converted to %IACS | ≥ 96 % IACS for copper, with the sample count and temperature stated — a ratio, not an adjective |
| Clad-layer thickness and bond | Polished cross-section, etched, imaged at 200×+ | Photograph plus a measured thickness; “no interface visible” is the finding you want |
| Contact drift on the suspect conductor | Crimp, cycle thermally, measure mV-method resistance | ΔR with the cycle/temperature profile; compare against the same plug on certified copper from the same lot |
| Hardness and proof stress of pin stock | Microhardness on a mounted blade; tensile-derived proof stress if required | HV range and 0.2 % proof stress for the named coil, before you buy the tooling decision |
The clause nobody can sign, and why that is worth knowing. No connector maker can certify a third party’s cable, and a supplier who countersigns a “100 % copper” statement they never tested has just told you what their signature is worth. The realistic division of duty: the cable producer declares the conductor metal against a mill certificate, the integrator spot-checks with tests 1–4 at the dock, and the connector supplier warrants only what happens at its own interface. Keep those three separated in writing and post-failure arguments get shorter — and expect the pop-outs, the drift and the cracked housings to be filed against the connector anyway, whoever caused them.
10. The receiving-dock checklist
Nine checks. The first five take under ten minutes and reject most of what is out there.
- Read the label for a conductor material statement, not a category claim. “Cat6” is not a metal.
- Weigh the box; compare against the copper arithmetic for the stated AWG and length (section 3 / test 1).
- Strip 300 mm and run a magnet over both the conductor and ten loose plugs.
- Measure one conductor four-wire; divide by length over area; compare to 0.0172 Ω·mm²/m.
- Cut, polish or cleanly snip, and look at the end at magnification: uniform metal, or a ring.
- Do a bend test on a strand — fold it back and forth. Copper work-hardens slowly and warns you; clad and steel crack or snap early.
- Terminate one plug, measure per-conductor pull-out, and note whether the metal bit or slipped.
- Keep the retained samples: 2 m of jacket and 10 plugs per lot, labeled with the lot number, for two years.
- Write the result on the goods-receipt note, not in an email. A claim filed eighteen months later is only worth what the paperwork says.
Frequently asked questions
Is CCA ever acceptable?
Not as category cable, and not in anything carrying PoE. Where clad conductors do appear legitimately is in applications that are neither: some coaxial and magnet-wire constructions specify clad steel by design, with the electrical consequences engineered in. If someone offers you “CCA Cat6” as a cost-down, they are offering you a different product with a borrowed name, at a length where the resistance penalty is real.
We use short patch cords only. Do we care?
Less, and specifically: less on fixed runs and more on the cords themselves, because fine-gauge patch cords already spend most of the DC budget. On a 26 AWG cord, copper alone gives about 13.4 Ω per 100 m per conductor, so a 5 m cord is trivial — the place clad stock bites on a cord is heat at the connector when the PD draws Type 4, and brittleness at the next re-termination.
Does thicker gold help with a clad conductor?
No, and it can make matters look better for longer. Gold protects the contact interface; it does nothing about an oxide forming on the aluminum inside the bite, nor about creep relaxing the clamp. It also does nothing about the channel resistance, which is where the budget is spent. The plating discussion is covered in the gold plating guide, where the conclusion is that thickness buys corrosion and cycle margin, not conductivity for the run.
Can a plug be made to tolerate aluminum conductors?
Some connector families are designed for it: crimp sleeves, compliant tines, anti-oxidant compound, disc-spring washers and torque-controlled lugs all exist in building wiring for aluminum. An 8P8C modular plug is none of those things — its geometry assumes a ductile copper conductor that will flow into the tine windows and stay there. You can specify a plug that does less damage on clad wire; you cannot specify one that makes the joint aluminum-correct. Which is why the conductor gets tested rather than the connector re-engineered.
Why does the installer get blamed, and the connector get the chargeback?
Because the connector is the visible part of a joint whose other half is a rolled metal you cannot see inside a jacket. Symptom overlap is total: popped pin, intermittent on touch, high-resistance joint, one pair reading differently from the others. Run the pull-out test and the resistance test on the same termination — the first belongs to the termination process and the second to the metal, and it is the second one that usually closes the argument.
Who normally verifies conductor material on a project?
Rarely, and that gap is where the losses hide. In a typical project the cable producer issues a certificate of conformance asserting conductor material, the integrator never measures it, and the connector supplier warrants only the component. What closes the gap is boring and cheap: a goods-receipt line carrying the sampled conductor’s mass and four-wire resistance, with initials and a date, plus retained samples per lot. Putting a written DC-resistance record into the cable order moves the duty to the party who can measure it at extrusion — the only stage where catching it is still economic.
What is the smallest test that catches most of it?
Mass and resistance, in that order. A 60 % conductor-mass shortfall is not explainable by any legitimate tolerance, and a resistivity more than about 15 % above the copper constant is not copper. Both need a scale and a meter, and neither needs a laboratory.
We bought 40 reels already. Now what?
Do not pull them out of service on a hunch; do the arithmetic. Take three reels, run tests 1, 3 and 4, and compute the loop DCR of your longest installed run against the section 3 table at the class of PoE you actually run. If copper values hold and the runs sit inside budget, you have a documented lot to work through on schedule. If resistance reads high, stop terminating and re-quote the job with certified cable — because the warranty cost of a PoE reboot at month fourteen is measured in truck rolls, not in per-meter price.
Sources and standards referenced
- ANSI/TIA-568.2-D — balanced twisted-pair cabling components and permanent-link requirements, including the copper-conductor basis for category cable and the DC resistance unbalance limits. Confirm the revision you cite; the loop-resistance ceiling mentioned on this page is a commonly specified figure rather than one quoted from memory, so check it in the edition you hold.
- ISO/IEC 11801 series — generic cabling and component specifications, same conductor-material basis.
- IEEE Std 802.3bt-2018 — PSE/PD types, classes and per-pair currents; the reason channel DC resistance is a power parameter and not only a data parameter.
- TIA TSB-184-A / -A-1 — power distribution over balanced twisted pair and bundle heating, the derating context in which a resistance multiplier stops being academic.
- ASTM B3 — annealed copper wire: the DC resistance constant used for every computed figure on this page (0.017241 Ω·mm²/m at 20 °C). ASTM B33 for tinned stranded copper.
- IEC 60512 series — contact resistance by the millivolt method, endurance, and wire-retention test procedures used in sections 6 and 9.2. Select the test part and edition in your own report.
- ASTM B117 — salt-spray practice, at the 24 and 48 hour exposures commonly quoted for connector contacts.
- UL 94 — flammability classification of housing polymers; relevant to the regrind discussion in section 5.
- Material properties quoted as ratios (density copper ≈ 8.96 vs aluminum ≈ 2.70 g/cm³; resistivity ≈ 1.68–1.72 vs 2.65–2.82 × 10⁻⁸ Ω·m; thermal expansion ≈ 17 vs 23 µm/m·K; aluminum ≈ 61 % IACS) are published handbook values used here for order-of-magnitude arithmetic, not measurements of any particular reel.
On the numbers in this article. Every resistance, mass and loss figure is computed from geometry and published constants in the open, so anyone can rerun it for their own AWG and length: they are arithmetic, not test results, and not a compliance verdict on any particular cable. For reference, a well-documented connector data sheet in this category states an initial contact resistance around 20 mΩ with its method, gold thickness of 3–50 µ” measured per batch by XRF to ±0.2 µ”, 24–48 h ASTM B117 exposure, ≥ 750 mating cycles and virgin polycarbonate with a UL 94 class — those are the row labels worth asking for, not endorsements of any supplier. No “typical” resistivity for anyone’s cable appears anywhere on this page: that number can only come out of the reel in question.
What to do with this
- Pick the three cable part numbers you buy most and run tests 1, 2 and 3 from section 6 on a sample of each. Two hours and a scale; most of the fraud in the world is caught at this step alone.
- Put the 9.1 clauses into the next cable order, not the next connector order — that is where the conductor declaration belongs.
- Before blaming a termination, write down the loop resistance of the run and compare it to section 3. The number either clears the connector or convicts the metal, and it costs a multimeter and a calculator.
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