EMI and EMC Considerations for Connectors and Harnesses

Connectors and harnesses across aerospace, defense, and industrial electrical systems serve to facilitate reliable signal transmission and power distribution.There are many technical factors that engineers must evaluate when integrating these assemblies, but electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are particularly vital considerations. Uncontrolled EMI can lead to data corruption, functional malfunctions, and failed regulatory testing, while insufficient EMC leaves systems vulnerable to such interference. To help you avoid these pitfalls, this blog will cover some practical guidance for selecting connectors and harnesses with EMI and EMC considerations in mind.

Understanding Connectors and Harnesses

Before addressing EMI mitigation and EMC in detail, it is important to have a baseline understanding of the roles that connectors and harnesses each play and their most typical forms. 

Connectors

Connectors are the interfaces between separate electrical subsystems, providing both mechanical coupling and electrical continuity. The two most-utilized variants include:

• Circular Connectors: Characterized by a cylindrical shell and a round mating interface, circular connectors often use threaded, bayonet, or push-pull coupling mechanisms to maintain secure connections under vibration and mechanical stress.
  
• Rectangular Connectors: With rectangular housings and linear contact arrangements, these connectors are designed to accommodate a high number of contacts within a relatively compact footprint. Usually, they are secured with panel-mount hardware, jackscrews, latches, or locking levers.

In these styles, there are also subtypes that incorporate additional conductive elements like shielded shells and internal filtering components to manage electromagnetic effects. Furthermore, connector shell materials and surface finishes have a large impact on performance. Aluminum or stainless steel are popular choices, which are then treated with conductive, corrosion-resistant finishes like electroless nickel or cadmium to maintain electrical continuity and shielding effectiveness over a long lifespan.

Harnesses

Harnesses are structured assemblies of wires or cables that organize and protect electrical pathways throughout a system. The most common approaches to harnesses include:

• Bundled Harnesses: This is the most basic harness configuration, where multiple wires or cables are grouped together using lacing, ties, or protective sleeving.
• Overbraided or Jacketed Harnesses: These harnesses incorporate an outer braid or jacket that surrounds the entire assembly for additional protection against abrasion and environmental factors.
• High-Density or Integrated Harnesses: Often driven by space, weight, and routing limitations in advanced aerospace and electronic systems, these harnesses accommodate a much higher number of small-gauge conductors that are routed very closely.

Across all forms, construction choices like conductor spacing, insulation type, and protective coverings directly influence how electrical signals are managed by the harness, making them central to EMI mitigation strategies.

How to Select Connectors and Harnesses with Appropriate EMI and EMC Characteristics

Not every system requires extensive shielding against EMI or careful attention to EMC, but the following scenarios mandate it:

• High-Speed Digital and RF Systems: Systems transmitting high-frequency or high-speed data signals are very sensitive to EMI, as it can cause signal degradation, data errors, or emissions that interfere with nearby electronics.
• Dense Electronic Environments: Platforms with high component density, such as modern aircraft or spacecraft, generate complex electromagnetic fields that could affect neighboring circuits, so EMC is necessary to keep all components operating without mutual interference.
• Mission-Critical Functions: Life-safety systems, navigation and flight control electronics, and communication arrays are expected to stay functional even in the presence of external electromagnetic disturbances. EMC is vital to manage, as these systems must limit emissions while also resisting interference from external sources.
• Challenging Environmental and Operational Conditions: Vibration can loosen connector contacts or cause shielding gaps, whereas moisture or contaminants can cause corrosion or conductive paths where there should be insulation. As such, connectors and harnesses need to be selected with the proper materials and sealing to perform under these expected conditions.
• Aerospace and Defense Systems: Industry standards define both allowable emissions and required immunity to external electromagnetic disturbances. For instance, RTCA DO-160 covers environmental conditions and test procedures for airborne equipment, while MIL-STD-461 sets EMI/EMC requirements for military equipment.

This being said, there are various aspects that go into properly integrating connectors and harnesses into such setups.

Shielded Components

EMI shielding is one of the main defenses against electrically noisy environments, with some specific features to look out for including:

• Backshells: While a metal connector shell provides a baseline conductive barrier, a dedicated EMI backshell presents a 360° electrical bond between the cable shield and the connector housing. As such, it can eliminate gaps where electromagnetic energy may leak and offer additional strain relief.
• Cable and Harness Shielding: Dual-layer or multilayer shielding helps attenuate electromagnetic interference across a broad frequency range. This can either be something like conductive foil wrapped around individual conductors or a braided metal shield surrounding the cable or harness. Notably, shielded cables must be electrically terminated around the entire circumference of the connector interface to avoid potentially becoming a source of interference.
• Twisted-Pair Conductor Arrangements: Twisting conductors within a cable helps minimize differential-mode noise and reduce crosstalk between adjacent signal lines.

Sourcing and Installation Practices

When sourcing connectors and harnesses with the previous attributes, always review accompanying listing information and documents to confirm their EMI shielding performance, material properties, and compliance with relevant standards. Once the right components have been selected, a robust grounding strategy further aids in directing unwanted electromagnetic energy away from sensitive circuits. Aim to create assemblies with:

• Low-Impedance Ground Paths: Establishing a direct, low-impedance connection between shield and chassis helps ensure that EMI is efficiently dissipated rather than introduced into the circuitry.
• Routing Separation: Separating noisy power cables from sensitive signal paths can prevent inductive coupling and reduce the potential for EMI-induced errors.
• No Ground Loops: Carefully planned grounding arrangements involving controlled grounding points and isolated return paths prevent unintended current paths that can generate interference.

Even with careful attention given to these factors, it is imperative to conduct in-system testing under expected operational conditions to validate performance before deployment. This extra confirmation will help you catch unforeseen interference issues and inform any next steps for mitigation.

Procure In-Demand Connectors and Harnesses from ASAP Aerospace

As we have covered, properly setting up connectors and harnesses to avoid EMI is fundamental to the success of complex electrical systems. If you are seeking a trustworthy source to secure these components, ASAP Aerospace offers thousands of options that meet strict industry standards. Presenting connectors, harnesses, and countless other products from reputable manufacturers, you can conveniently shop for everything you need on this platform. We look forward to serving you with competitive procurement solutions, so be sure to explore our selection and connect with our expert team at your earliest convenience!