Appendix: Quick-Reference Tables
These are deliberately kept as compact lookup tables — IP ratings (A1), 38999 contact sizes (A2), and a family-selection quick guide (A3). Use the contents panel to jump between them. Every value is an orientation aid to verify against the source, not a selection rule. For scenario-by-scenario reasoning, see the Decision Paths.
A catalog rating is not a permission slip. Current, voltage, temperature, sealing, and mating-cycle limits depend on the exact contact, wire gauge, number of loaded circuits, ambient temperature, enclosure heat, termination quality, assembly process, and allowable temperature rise. Use these tables as a screening tool first; use the exact datasheet, derating curve, application specification, and program/customer requirement for design release.
A1. IP rating reference
IP codes are commonly referenced from IEC 60529.1 The high-pressure washdown rating IP69K comes from ISO 20653 (a DIN-style lineage, formerly DIN 40050-9), not IEC 605292 — IEC 60529 added a close equivalent, IPx9, in its 2013 edition. Verify the exact standard cited by the manufacturer, the specific depth/duration for any IP68 claim, and remember that an IP rating applies to the tested assembly/configuration, not automatically to the entire system — confirm whether the rating applies mated, unmated, capped, panel-mounted, torqued, strain-relieved, or with specific wire seals/cavity plugs installed. Note also that the immersion tests (IPx7/IPx8) and the jet tests (IPx5/IPx6/IPx9) are independent — passing immersion does not imply jet protection, which is why washdown parts are often dual-rated (e.g. "IP67/IP69K").
| IP | Solid ingress | Liquid ingress | Typical application |
|---|---|---|---|
| IP54 | Dust-protected; limited ingress permitted | Splash from any direction | Sheltered outdoor equipment |
| IP65 | Dust-tight | Low-pressure jets, any direction | Outdoor enclosures, wash-down areas |
| IP67 | Dust-tight | ~1 m immersion, ~30 min (per standard test) | Many industrial field connectors |
| IP68 | Dust-tight | Manufacturer-stated depth/duration | Subsea, submerged sensors |
| IP69K / IPx9 | Dust-tight | High-pressure, high-temp jets. "K" is per ISO 20653, not IEC 60529 | Washdown, food processing, vehicles, agriculture |
A2. 38999 contact sizes — example test values (verify per contact P/N)
| Size | Matching wire (AWG) | Spec test current (example) | Notes |
|---|---|---|---|
| 22D | 22 | 3 A | High-density signal |
| 20 | 20 | 5 A | General-purpose signal / light power |
| 16 | 16 | 10 A | Moderate power |
| 12 | 12 | 17 A | Higher-current power |
| 8 / larger | per catalog | power contacts | High current; coax/twinax in size 8 |
Test currents from a manufacturer contact-performance spec — a different, lower parameter than the contact's free-air current-carrying rating (e.g. size 16 ≈ 13 A carrying vs. 10 A test), and not a universal continuous rating. Size against the actual contact datasheet and derating curve.3
A3. Family selection quick guide
| Need | Consider | Prefer an alternative / avoid |
|---|---|---|
| Mil-spec flight/defense harness | MIL-DTL-38999 Series III | Commercial circular, M12 |
| Industrial sensor connection | M12 A-coded | D-sub, hobby connectors |
| Industrial Ethernet (GbE) | M12 X-coded | M12 D-coded, exposed RJ45 |
| Machine umbilical (power+signal+data) | Industrial rectangular / Han-Modular | Many individual small connectors |
| Serial/debug, benign environment | Micro-D, MIL-grade D-sub, keyed header | Bare headers, exposed USB |
| High-current robot power (>20 A) | Anderson SB, Han-style power insert, 38999 size 8/larger or dedicated power contacts (HCP = high-current power, or RADSOK4); size 12 only where derating supports it | M12 A-coded, XT60/90, 38999 size 16 for the full load |
| Internal protected PCB harness | Molex Micro-Fit, TE, Harwin | Bare wire, 0.1" headers, screw terminals on PCB |
| Fast quick-disconnect, moderate vibration | MIL-DTL-26482 bayonet (verify qualification for the vibration profile) | 38999 threaded (slower to mate) |
| RF/antenna/GPS line | SMA/TNC/N-Type (impedance-matched) | Random circular signal contacts |
| Hybrid power+RF+control to one payload | 38999 hybrid insert (coax + power + signal contacts) | Separate connectors if panel space is scarce |
A4. Typical mating-cycle life by family
Rated mate/unmate cycles vary widely. Design with margin below the rated number for the service model (production-only, test, or field-service).
| Family | Typical rated mating cycles |
|---|---|
| Molex Micro-Fit 3.0 | ~30 (up to ~250 with lubricated RMF terminals)5 |
| MIL-DTL-38999 / MIL-DTL-26482 | 5006 |
| Micro-D (MIL-DTL-83513) | 5006 |
| D-sub (MIL-DTL-24308) | 5006 |
| M12 (screw-lock) | ≥ 100 (per datasheet)7 |
| Industrial rectangular / Han | ~500 standard; Han HMC (high mating cycle) far higher8 |
| USB-C | 10,000 (USB Type-C spec)9 |
Cycle life is a durability figure only — not a measure of sealing, vibration, or ruggedness. Verify against the exact part's datasheet.
Final Note
Every connector decision ripples outward — into the cable drawing, the ICD, the tooling budget, the assembly procedure, the maintenance manual, and the failure log. Engineers who treat connectors as commodities buy them on pin count and regret it. Engineers who treat them as system interfaces design reliable, serviceable, manufacturable hardware.
When this guide conflicts with a manufacturer datasheet, applicable standard, customer requirement, or qualified program requirement, the datasheet / standard / customer requirement wins. This document is a framework for thinking, not a source of record.