EMC: Three minor design flaws with major consequences
EMC issues often don’t arise only in the test lab. They frequently begin much earlier—with seemingly minor details in the design, wiring, or assembly.
The tricky part is this: a system can work perfectly well in theory but still cause problems in real-world use. During testing, everything runs smoothly, but later on, communication drops, malfunctions, or sporadic failures suddenly occur. That is exactly why it’s worth considering EMC early on.
1
When Cables Become Antennas
Cables are not just electrical connections. Depending on how they are installed, they can emit or pick up (frequencies) from the surrounding environment.
Long cables, large loops, or separate forward and return conductors are particularly problematic. Rapid switching operations, motors, relays, power supplies, or digital signals can also contribute to EMC issues if the cable routing is poorly designed.
The simple message: A poorly routed cable can act like an antenna.
2
When shielding only works on paper
A shielded cable does not automatically mean that a system is EMC-compliant. What matters is how the shield is connected.
Common problems include long connection wires, poor contact, or broken shield connections. In such cases, while the shield may be physically present, its effectiveness can be significantly lower than expected.
In practice, this means that the canopy should be attached as often as possible or across its entire surface. The installation method plays a key role in determining the final result.
3
When filters are installed in the wrong place
Passive filters are important components—but they only work reliably if they are properly positioned and connected.
If a filter is located too far from the source of interference, the interference may partially bypass the filter. Additionally, cables running parallel to the filter before and after it can reduce its effectiveness.
An input filter must be installed directly at the product’s input connector.
Therefore, a filter is not a magic solution. The installation location, ground connection, and cable routing are just as important as the component itself.
Why small mistakes can end up costing a lot
Entry and exit points are often difficult to identify because they do not always occur consistently. They depend on the environment, cable lengths, load conditions, or installation scenarios.
Many EMC issues can be avoided if EMC considerations are taken into account early on in the design, construction, and assembly phases.
This minimizes the risk of rework, additional inspections, on-site service calls, or project delays.
CONCLUSION
EMC is not a single component, but rather the result of the interplay between design, electronics, wiring, and assembly.
Wires can become antennas.
Shielding is effective only when properly implemented.
Filters are only effective if they are installed correctly.
By addressing these issues early on, you can minimize future risks—and ensure that systems not only function properly but also remain reliable in real-world use.
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