Cable and harness design
The cable is the antenna. Shield termination decides whether a system passes EMC, and it is a connector decision.
In most systems the boards are small and the cables are long. That makes the harness the dominant radiating structure, the dominant susceptibility path, and — after connectors — the dominant field failure.
It is also the part most often designed last, by whoever is left.
Shield termination is the whole game
A shielded cable is only shielded where the shield is connected, and how it is connected matters more than that it is.
360° termination at the connector body, bonded to chassis, keeps the shield continuous into the enclosure and gives the return current a low-impedance path that does not detour. A pigtail — the shield gathered to a wire and landed on a pin — puts inductance in series and stops working at exactly the frequencies you care about.
That choice is made when the connector is selected, not when the harness is built. Which is why harness architecture belongs in the same conversation as the enclosure and the EMC strategy.
What gets decided
| Decision | Driven by |
|---|---|
| Shielded or unshielded per run | Signal bandwidth, aggressor proximity, regulatory target |
| Termination method | Frequency of concern, environment, serviceability |
| Connector system | Ingress rating, temperature, vibration, mating cycles |
| Keying and polarity | Whether a field technician can mis-mate it — assume yes |
| Pin assignment | Segregating power from sensitive analogue and high-speed pairs |
| Routing and separation | Which runs may travel together and which never may |
| Bonding scheme | Where the chassis reference is, and that there is only one |
Documentation is the deliverable
A harness design is only as good as the drawing somebody builds from. Wire schedules with gauge, colour, length and termination per conductor. Connector tables with keying and orientation. Shield termination detail drawn, not described. Routing and tie-down points where they matter.
Ambiguity in that package does not produce a wrong harness — it produces a batch where each one is subtly different, which is far harder to debug.
Where this connects
Harness work is rarely standalone. It sits between the enclosure design that provides the bonding surfaces and the EMC strategy that determines what the shield has to achieve. We have produced client-facing shield-termination concepts for industrial circular connector systems as part of exactly that three-way conversation.
Drawings, schedules and termination details transfer to you in native format, under EU jurisdiction — so any builder you choose can work from them.
Common questions
Straight answers
Why does harness design belong with the electronics?
Because the cable is usually the largest antenna in the system, and whether it radiates is decided by how its shield terminates — which is a connector and enclosure decision made at architecture stage. Designing the boards and then handing the wiring to whoever assembles it is how a system that passed at board level fails at system level.
What is wrong with a pigtail shield connection?
A pigtail puts an inductor in series with the shield. At the frequencies that matter for radiated emissions, that inductance is enough that the shield stops being a shield and starts being a coupling path. Terminating 360 degrees at the connector body, bonded to chassis, is the difference between a cable that contains its energy and one that broadcasts it — and it is chosen, not fixed later.
How do you pick a connector system?
By environment and by service life, in that order. Ingress rating, temperature range, vibration and mating cycles narrow it faster than pin count does. Then keying and polarity so it cannot be mis-mated in the field, and a shell that can actually be bonded if the cable is shielded. Cost enters last, because the wrong connector is expensive in a way the datasheet does not show.
Do you build the harnesses?
No. We produce the architecture, the drawings, the wire schedule and the termination scheme; a harness builder makes them. Documentation quality is the deliverable — a drawing that leaves a builder guessing produces a batch of harnesses that are each slightly different, which is worse than one that is consistently wrong.
We already have a harness that fails EMC. Can you help?
Usually, and usually without rebuilding it. Send the test report and the harness drawing. A failure at a specific frequency and orientation is diagnostic, and cable-driven failures point to a short list of causes — termination method, bonding point, routing next to an aggressor, or missing filtering where the cable enters the enclosure.
Evidence
Where this has been applied
Flight-controller carrier for a tube-launched UAV
Teardown, clean-room re-implementation, and a rigid-flex carrier that fits inside a launch tube.
Edge-compute architecture for an unmanned surface vessel
Three architectures compared on real bandwidth budgets, so the platform decision was made on evidence rather than TOPS figures.