LLT ENGINEERING · Application analysis
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Connector Cable Diameter and Conductor Cross Section Checks
A waterproof connector selection is not finished when the conductor size fits the terminal. Conductor cross-section and cable outer diameter do different jobs — one matches contacts and load, the other matches clamp and seal. This guide explains what each value controls, how to run both checks against one part number, and what to do when only one fits.
Scope and boundaries
Applies to waterproof connector selection for equipment wiring and harness builds where one cable must match one part number. This article can explain why the two dimensions are checked separately and what each one controls, but the available material does not list per-model terminal ranges or seal ranges, so the exact limits for a candidate part number must be confirmed from its drawing and specification.
Why one cable needs two separate checks
Every cable that reaches connector selection carries two dimensions — a conductor cross-section and a jacket outer diameter — that are easy to file under one 'cable size' but answer different questions. Conductor cross-section and cable outer diameter are two separate checks: the conductor value decides whether the chosen contacts can carry the load, and the cable OD decides whether the clamping and sealing structure fits, so a selection is only confirmed when both numbers sit inside the ranges of the same part number.
Confusing the two is where mismatches begin: a terminal can accept the conductor while the rear seal never closes on the jacket, or the cable passes the clamp while the conductor is wrong for the contact.
Sources: Technical applicability · LLT selection guide
What the conductor cross-section controls
Conductor cross-section is specified per core in mm²; AWG values follow the wire-gauge correspondence given in the catalog. This number's first job is termination: each core must fall inside the conductor range of the chosen contact. Its second job is current. Rated current is marked per single contact or per a specified contact group, and when several cores carry power at the same time, conductor cross-section, ambient temperature and heat dissipation all influence temperature rise and allowable current. Catalog values are a first screen; final confirmation uses the part-number specification and temperature-rise verification under actual duty.
Hybrid layouts need the same discipline per group: in a '3+2' pinout the two contact groups carry their own current, voltage and wiring specifications, and the group ratings cannot be added into one machine rating.
Sources: Technical applicability · LLT selection guide
What the cable outer diameter controls
The cable outer diameter is the jacket diameter in mm, and it belongs to the mechanical side of the interface: rear clamping and the sealing structure. The cable outer diameter must fall inside the seal adaptation range of the chosen configuration; checking only that the product's upper limit is larger than the cable OD is not enough. An adaptation interval has two ends, so a jacket that is too thin needs the same check as one that is too thick.
Protection ratings sit on this fit. IP67 denotes dust protection and short-term immersion under test conditions defined in IEC 60529, and the stated conditions include a correctly mated and locked pair, intact seals, a cable of the specified outer diameter and a completed installation seal. Unmated ports and equipment openings are handled separately.
Sources: Technical applicability · IEC 60529 — Degrees of protection provided by enclosures · LLT selection guide
Why the same conductor size can still fail the fit
Two cables with identical conductor cross-section can arrive with different outer diameters, because core count, insulation build and jacket construction all change the finished OD. The OD therefore cannot be inferred from the conductor specification; it comes from the cable's data sheet or measurement.
The units keep the boundary clear: mm² is a cross-sectional area per core, mm is the length used for jacket OD, and AWG is a gauge number. AWG and mm² both describe conductor size and can be cross-referenced where the catalog gives the verified correspondence; neither replaces the OD line.
Sources: LLT selection guide · Technical applicability
A two-pass check sequence for harness builds
Run the two checks as two passes against the same part number.
Both ranges belong to a specific configuration, so the check runs on the candidate's drawing and specification, not a series-level headline value.
- Define the electrical task: working voltage, current, core count, and which cores are power or signal.
- Pass one, conductor: confirm each core's cross-section against the terminal conductor range of the candidate part number; check hybrid pinouts group by group.
- Get cable data from its own specification: jacket outer diameter, jacket material, length, flexibility, outlet direction, termination form.
- Pass two, OD: confirm the jacket OD falls inside the seal adaptation range of the same configuration, not merely below its upper limit.
- Match jacket material to routing: fixed or moving installation, bending, temperature and media exposure.
Sources: LLT selection guide · Technical applicability
When one value fits and the other does not
If the conductor cross-section is within the terminal range but the cable outer diameter is outside the seal range, stop and confirm a matching configuration instead of assuming the seal can be swapped; if both values fall inside the ranges of the same part number, proceed to assembly and sample verification. The reverse case — OD fits, conductor outside the terminal range — is the same stop: a cable that seals well but cannot be terminated correctly is not a valid match. Neither mismatch proves a defect has occurred; it marks the pairing as unconfirmed until the configuration is checked.
The closing documents belong to the part number: board thickness, panel cutout and locking follow the part-number drawing for panel-mount versions; torque and stripping dimensions follow the model's documentation. Handling and re-termination are done de-energized unless the documentation explicitly supports mating under load.
Sources: Technical applicability · LLT selection guide
What to submit for a matched cable and connector set
LLT can evaluate cable and connector as one assembly when the request carries the full picture. Include:
An existing sample or drawing can start the engineering review; custom designs complete the corresponding sample verification before release.
- interface drawing or mating part number, core count and wiring definition
- working voltage and current, with the split between power and signal cores
- conductor cross-section per core in mm², or AWG where a catalog correspondence applies
- cable outer diameter, jacket material, wire length and tolerance
- branch positions, outlet direction and tail treatment
- environment and verification requirements: rain, immersion, washdown, UV, salt spray, temperature range
Sources: LLT selection guide · Technical applicability
Frequently asked questions
The conductor size fits — is the selection done?
Not yet — that clears only the termination pass. The cable outer diameter must still fall inside the seal adaptation range of the same configuration; comparing only the product's upper limit with the cable OD is not enough. Confirm both against the part-number data.
Can a cable be specified by AWG alone?
AWG is a gauge numbering system and mm² states cross-sectional area per core; both describe conductor size and can be cross-referenced where the catalog gives the verified correspondence. Neither describes the jacket — the outer diameter in mm is the separate line that clamping and sealing depend on.
Same conductor size — why might only one of two cables seal?
Because the seal fits a diameter, not a conductor. Core count, insulation and jacket construction can give identical cross-sections different outer diameters, so each cable's OD is checked against the adaptation range; the matching conductor size does not answer that.