Shielded cables play a huge role in reducing radio frequency interference denoted as RFI as well as electromagnetic interference (EMI) from external devices like fluorescent lighting, air conditioners, cellular networks, power lines, and computers.
Furthermore, EMI has to do with those unwanted signals coming from a nearby transmission circuit. In addition, the shielded cables have the ability to prevent data transmitted from the EMI as well as cross-talk in-between the cable pairs, as well as unintended coupling. What results is a rise in the transmission speed and less data errors.
Reasons Why You Should Make Use of a Shielded Cable
You may think of making use of shielding cables if your office or home is overfilled with appliances and electronic devices or situated close to power lines.
Shielded cables that are well installed are usually designed to help in mitigating crosstalk and EMI coupled with ensuring the integrity of the data, as well as maintaining a great transmission performance and speed. Cable interference shielding doesn’t just prevent crosstalks in-between cables. It also plays a huge role in protecting devices and machines, as well as people.
Furthermore, cables inserted into enclosures, metal cabinets, or from other noise sources don’t need any shielding. This is because they already have some protection from EMI and noise. Also, take note that though shielding could make your cable more robust and rigid, they shouldn’t be utilized in any wet location. This can only happen if they are manufactured specifically for these applications.
Do Shielded Cables Come in Different Types?
The use of shielded cables is dependent on the application. Yes, shielded cables come in different types and they are readily available for purchase. However, the three main types that serve signal cables of low voltage include foil shield or Mylar (metal-coated), spiral design, or braid shield. With respect to the construction and design, cable shielding can help in noise reduction by at least 85%.
Braid Shielding
The braid shields are usually constructed through the weaving or copper wires and aluminum wires interlaced together. Also, braid shields can help in noise reduction to a maximum of 90%. In addition, braid shielding will help you cover around 85% of your wire. Also, signal noise could leak in-between the gaps present in the braided weave design.
In addition, the coverage amount has to be sufficient, most especially where some applications don’t need frequent movement flexing. One important thing to consider here is the disadvantage of braid shields design. It is usually more expensive and adds more weight to your final design.
Spiral Shields
Spiral shields are composed of conductive wire, which are wrapped in the form of a spiral surrounding the core of the inner cable. Also, this helps in mitigating noise to a maximum level of 98%.
Just like braids, you can make use of different materials as well as wire sizes. However, these spiral shields only work for mid-sized and smaller cables to help in attaining a greater coverage. Also, they are well-suited for different audio applications and audio frequency range.
Foil Shields
The foil shields usually make use of aluminum foil laminated to a polypropylene or polyester film. Foil shielding has the ability to offer full cable coverage, offer strength, as well as add the needed insulation for the shield protection.
Furthermore, foil shield helps in getting rid of gaps present with the braided designs in deflecting EMI 100%. Foil shielding fails to perform effectively in any high-flex applications in contrast to the braided or spiral designs. However, foil shields possess less weight and are less expensive than the braid or spiral shields.
Ensure that shielded cables are properly grounded on the two ends. This is to enjoy all the benefits that shielding has to offer.
Multi-Shield
It is possible to construct cables with many multiple shielding layers utilizing both the foil and braided designs for the noisy environments. Furthermore, the communication cables can be individually shielded after pairing. This will go further to help prevent coupling and cross talk.
What Shielding Type is Best for You?
The best shielding for all applications has to do with the application in question. The designing of twisted wires is to reduce some of the EMI present in the unshielded cables. However, the extra shielding present in the twisted shielded wire cables is much more effective in the protection of interference.
Furthermore, shielded cables have to be used along with the shielded connectors having some casing or metallic screen, which absorb RFI/EMI and also channels any interference that is unwanted to ground connection.
In addition, the efficiency of shielding is usually affected by the resistance. This makes shields that are wire-based like braids and spirals shielding great for applications with lower frequencies. Also, coverage is known as the major issue when it comes to higher frequencies that makes foil shields having 100% coverage the most appropriate option, most especially in communication and network cables.
How to Choose the Most Appropriate Shielding
Low-Frequency Applications
Spiral or braid shields are usually useful for applications of low frequency (about 1 MHz). Also, for the low frequencies, a shield’s electrical resistance is a very important factor that helps it become effective.
Medium-Frequency Applications
The usefulness of braid shields can be seen in applications with medium frequency, ranging from 1MHz – 100 MHz. Furthermore, the effectiveness of the braid shield has to do with the coverage that it offers, as well as the weave’s tightness. Coverage from the braided shield falls between 65% – 98%. In addition, higher braid coverage causes greater shield performance; however, it usually costs more.
High-Frequency Applications
The combination shields can be viewed as the best, when dealing with high-frequency applications. This is usually higher than 100 MHz. When you combine the foil shield with the braided shield, the energy leaks, which usually come from the braided shield, are blocked.
Conclusion
The main purpose of cable shielding is grinding noise, which the cable picks up. Cable shielding as well as its termination has to offer a very low impedance path into the ground. The shielded cable which isn’t grounded causes disruptions, which could increase the impedance level, as well as reduce the cable’s effectiveness.
