A Deep Dive into Shielded Cable: Types and Benefits

The efficiency of electronic communication in the modern digital era relies heavily on the cables that carry signals. And shielded cables stand out for their ability to maintain signal integrity and reduce interference in a variety of applications. Unlike unshielded wires, shielded cables incorporate conductive sheathing to block electrical noise. This blog delves into shielded wire types, differences from unshielded cables, and best practices for installation and grounding.

 

What is Shielded Wire?

Shielded cable, or screened cable, is an electrical cable with conductors surrounded by a conductive layer that is usually made of metal foil or braid for electromagnetic shielding. The shield serves as a protective barrier against external electromagnetic interference, safeguarding the cable’s internal conductors to preserve the transmitted signal’s integrity, and can be grounded to bolster protection against electric fields; certain shielded power cable designs also utilize the shield as a return path for the signal. Shielded cable symbol is typically a line with smaller lines running parallel to it, indicating the shield around the cable.

shilded cable

Shielded wires are used in various applications where safeguarding against interference and preserving signal integrity are paramount, including networking, professional audio and video, security systems, and industrial control systems. Shielded cables are particularly vital in environments subject to high electromagnetic interference, such as airports and radio facilities. Standard shielded cable specifications are shielded wire cable 4 core, shielded cable 3 core, and shielded cable 2 core. Having established what shielded wires are, we now turn to shielded wire types.

 

What are the Shielded Cable Types?

There are five main shielded cable types available in the market, namely, twisted pair, foil shielded cables, braided shielded wires, spiral shielded cables, and combination braided cables, each of which is suitable for a particular application and has its advantages and disadvantages:

  • Twisted Pair: also known as unshielded twisted pair (UTP), although not shielded, UTP cables are worth mentioning as they utilize twisted pair to reduce EMI without a physical shield. UTP is the most common type of networking cable due to its simplified construction and ability to maintain signal integrity.
  • Foil Shielding: Foil screened cable utilizes a thin layer of aluminum foil that covers the entire set of conductors and is usually terminated (grounded) with a drain wire. Aluminum foil shielding is excellent at preventing high-frequency EMI. Still, it has less physical strength and limited flex life than braided shielding and is typically used in multi-core data cables, such as Cat5e and cat6 shielded cables, to provide crosstalk protection between pairs.foil shilded cable
  • Braided Shielding Cable: Comprises interwoven copper or aluminum strands that provide good flexibility and are effective at shielding against low-frequency interference. Typical coverage of braided shields ranges from 70% to 95%; the higher the coverage, the better the protection. Braiding metal shielded wire may diffuse a small proportion of incident EMI to pass through to the inner signal and is commonly used in audio and video cables and in some types of data transmission cables. Braided cables are heavier and have a larger cable diameter than aluminum foil-shielded electrical cables.
  • Spiral Shielding: A variant of braided shielding, consisting of copper wire wound in a spiral around a conductor. Spiral shielded wires are flexible and suitable for applications where the cable will be moved or flexed frequently, such as in microphone or instrument cables.  However, like braid shielding, it has an increased weight and diameter, and is relatively difficult to terminate.
  • Combination Shielding: Combines foil and braided shielding to maximize protection against EMI across a comprehensive range of frequencies. The foil provides coverage against high-frequency interference, while the braid adds strength and protects against lower-frequency interference. Combined shielding is often found in high-performance data transmission cables.

Shielded Cable Type Comparison

Each cable shielding type is designed to meet specific challenges, and the comprehensive selection requires evaluating the signal frequency, flexibility needs, physical durability, and operating environment. For example, braided shields work well for flexible low-frequency connections, while foil shields are better for high frequencies in stable environments. Choosing the right type of cable shielding can maximize system efficiency and longevity. After examining the various types of wire shielding, let’s consider how screened cables differ from unshielded electrical wires.

 

What is the Difference Between Shielded and Unshielded Cable?

The main difference between shielded and unshielded wires is their capacity for electromagnetic interference mitigation. Shielded cables are equipped with an outer conductive layer that protects against EMI and maintains signal integrity, making them ideal for high-interference environments and sensitive data transmission. In contrast, unshielded cables lack this protective layer and are susceptible to external noise that can damage electrical systems.

But it’s worth noting that though shielded wires provide higher protection against EMI, ensuring data integrity, they are more expensive and less flexible than unshielded cables. On the other hand, unshielded cables are easier to install and maintain and are more cost-effective, though they can’t protected from EMI.

The choice of shielded cable vs unshielded depends on the specific EMI requirements of the application. Clean, controlled residential and office settings typically have less electromagnetic interference, making unshielded cables a practical choice. Conversely, harsher, outdoor, or moisture-prone settings with higher interference potential necessitate the use of shielded wires to ensure system reliability and signal integrity, like industrial settings, hospitals, and areas with many electronic devices. Understanding these differences leads us to the practical question of how to shield an unshielded cable.

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How to Shield Cables from Interference?

The best way to keep cables free from interference is to use cables with built-in shielding, like shielding control cable, or shielded automotive wire with metal shielded wire. However, a customized shielding solution for existing cables can be an effective measure for sensitive electronic equipment environments where external noise is prevalent. The following is a step-by-step guide to DIY cable shielding:

Step 1. Determine which cable needs additional shielding.

Step 2. Cut a piece of aluminum or copper foil that is long and wide enough to fit.

Step 3. Wrap the foil around the cable. Ensure that you cover it entirely and that the foil overlaps.

Step 4. With the foil in place, cover the foil and cable with heat shrink tubing and shrink the tubing with a heat gun. If you don’t have heat shrink tubing, electrical tape can also secure and insulate the foil.

Step 5. For cables subject to high-frequency noise, ferrite heads or cores can be inserted at both ends of the cable to suppress high-frequency noise by increasing the cable’s impedance to specific frequencies.

Step 6. Test shielded cable wire for proper function and interference reduction with EMI/RFI detector.

There are typically three types of cable shielding: one encases the cable in a layer of thin aluminum foil, another employs a braided shield around the cable, and a third type combines both foil and braid for enhanced protection. We diy generally use the foil shielding method. DIY cable shielding can be an effective way to reduce interference, but care should be taken that cables are installed away from potential sources of interference, such as power lines, transformers, and motors. If the cable must be routed through these sources, route it at a 90-degree angle to minimize inductive coupling. Having discussed how to shield cables, grounding shielded cables is another vital aspect to consider.

 

Do You Ground Both Ends of a Shielded Cable?

Whether to ground both ends of a screened cable is not a straightforward question and depends on the specific circumstances:

Single-End Grounding: Grounding the shield of a cable at a single point, commonly at the source end, is widely used in audio and other sensitive low-frequency applications to prevent ground loops. This method provides a safe path for induced currents while maintaining ground isolation between connected devices. By grounding the shield at a single point, any electrical noise captured by the shield is directed to the single-point ground without creating a loop that might act as an antenna for interference.When implementing single-end grounding, ensuring that the ungrounded end is terminated correctly is essential to prevent the shield from picking up noise.

Double-End Grounding: For high-frequency applications and environments with substantial electromagnetic interference, double-ended grounding of screened cables may provide enhanced noise immunity by reducing common-mode signals. RF coaxial cables used in antennas, transmitters, and receivers are typically grounded at both ends. When the shield is grounded at both ends, it can act as an effective Faraday cage to mitigate interference. However, care must be taken when the shield concurrently carries a return signal, as ground potential differences can induce loops and coupled noise. In such cases, ground loop isolators may be employed to break the loop without compromising shielding.

Single-point grounding in low-frequency applications can help reduce interference and minimize ground loops. Whereas in high-frequency situations, grounding at both ends may be beneficial to minimize EMI, but vigilance should be exercised. The choice of single- or double-ended grounding ultimately depends on the electromagnetic environment, signal frequency, and system design. If you are confused, asking for the manufacturer’s advice is a wise approach.

Conclusion

All in all, shielded cables are indispensable in the digital age, playing a pivotal role in ensuring seamless communication by providing robust protection against electromagnetic interference. Selecting the appropriate cable type and adhering to best practices in installation and grounding is critical for maintaining signal integrity. As digital communication systems continue to evolve, the importance of emc shielded cables provided by leading companies such as ZW Cable in enabling reliable electronic switching remainsunquestioned.

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About Me
Richard Zi
Richard Zi

My name is Richard Zi, and serve as the General Manager of ZW Cable. With a deep and extensive background of more than 15 years in the cable industry, I am excited to share my wealth of knowledge and experience.ZW Cable is a renowned company in the field of cable manufacturing in world, we specialize in selecting the best cable sizes and effectively solving all your cable challenges. If you have any questions or needs regarding cable solutions, please contact me and I assure you of the highest standards of personalized and effective guidance and support.View All My Posts >>

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