Anytime there is data being transferred, there can be interference from the electrical field. In order to cut down on electromagnetic interference, shielded cables are employed. It is important to understand cable shielding so that your cables work the way the manufacturers intended. Here is a description from Remee Wire & Cable about what cable shielding is, what it is used for, and why it is important to your business.
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Electrical cables can be made of several wires bound together. Cable shielding acts to protect the wires with electrical current from interference from those free electrons floating in the field as well as interference from other wires in the cable.
Think about a cross-section of your cable. If you look at the inside of your cable, you will notice that the cable itself is wrapped in a shield for protection from outside interference.
A cross-section of cables can include several conductors that are also wrapped or shielded. These wires within the cable need to be shielded so they are protected from interference.
If you do not have cable shielding on your cables, your project is apt to be less expensive when you begin it. However, without cable shielding, all sorts of problems may occur. For example, without shielding, your cables are open to electrical interference, which can cause a disruption in signal from the cable itself.
If you have cable telecommunications lines, for example, interference with the signal could cause the signal to be interrupted constantly, which leads to many unhappy customers. All of your quad shield coax cables, shielded ethernet cables, shielded network cables, and shielded USB cables must be adequately shielded to keep your networks healthy and your customers happy.
Unshielded cables have a much larger rate of interference than shielded cables, which means that you may have to constantly stop your work to look at periods of electrical disruption and electrical devices that quickly wear out.
Several types of shielding cable exist to preserve the cable’s integrity and signal strength. Here are the most common types of cable shielding found in markets throughout the United States.
Braid shields, also called metallic braid shields, are among the most common types of shielding available. While the name braid shields may sound strange, these shields get their name because they are woven around conductors in a similar way that people can braid material or hair. Usually, these braid shields are made of tinned copper or bare copper strands.
Braid shields have some advantages over other types of cable shielding. They are more flexible and stronger, can be used with all frequencies, and can physically protect your cable from interference.
Foil shields are constructed of composite aluminum and Mylar tape. There are many advantages to using foil shields. They are less expensive than braided shields, and they have a drain wire within the cable shield that allows easier grounding of the cables.
Foil shields can face inward or outward, depending on what your needs are. Foil shields are thin and very light. They can be applied easily. While foil shields are flexible, their flexibility has a shorter lifespan than other shields, so you may have to replace them more frequently. Foil shields offer very little protection for a cable, and they have no mechanical strength. Often, businesses use the combination of foil shields with braided shields for maximum performance and durability.
Spiral shields may sound very much like braided shields, but there are distinct differences. Spiral shields wrap around the wire in one direction, usually clockwise, but there are reverse spiral shields that are wrapped over the wire in the opposite direction.
Spiral shields are economical, easy to set up, and are very flexible. You can terminate spiral shields much more easily than other shield types. However, spiral shields are delicate, and they have limited frequency coverage, which means they are restricted to audio use.
Tape shields are very much like foil shields in many respects. Tape shields are wrapped around conductors, often in a spiral fashion. While they are easy and economical to produce, tape shields have drawbacks as well. You must use a drain wire, and they do not offer much physical protection or mechanical strength.
The demand for shielding to combat the effects of EMI in industrial applications is on the rise. This is where shielded cables come in.
Although electrical noise is common on factory floors, it should not be overlooked. For one, this interference can disrupt the proper operation of other equipment.
The primary way to stop unwanted noise in cables is through shielding. Shielded cables have various degrees of shielding and effectiveness, depending on several factors.
Thus, it is important to understand how they work and where to apply them best. This guide will introduce shielded cables – with all the basics you need to know.
Electrical cables will radiate energy to, and pick up energy from, their surroundings. Shielding stops that EM energy radiated by a cable, protecting nearby sensitive equipment.
Generally, shielded cables function as electromagnetic energy interceptors. It prevents EMI from travelling to the centre conductor and cutting off the data signal. This means an improved ability to reject noise and handle gigabit Ethernet—all the good stuff!
EMI stands for electromagnetic interference. It is the unwanted noise or interference in an electrical path or circuit due to an outside source.
Besides that, shielding gives protection against damage from cable motion and use. A well-shielded cable can also keep out unwanted external interference.
Shielding in cable has a conductive layer around its conductors for electromagnetic shielding. It is usually made with foil or braided metal strands.
These strands are often tinned copper, bare copper, aluminium, or other conductive material. But in most cases, you will see them with foil and/or braids, particularly in networking cable.
Standard cables can be the main transfer source for EMI, both as a source and receiver. As a source, it can conduct noise to other equipment or act as an antenna radiating noise.
As a receiver, it can pick up EMI radiated from other sources. A shield works on both, surrounding the inner signal- or power-carrying conductors.
Simply put, the shield can act on EMI in two (2) ways: 1.) it reflects the energy, 2.) it picks up the noise and conducts it to the ground.
Shielded cables are thicker and more rigid than their unshielded counterparts. They also require greater care when working with them.
Shielded cables are most often found in industrial settings. Plus, in installations where nearby equipment is likely to generate electromagnetic interference.
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Meanwhile, unshielded ones are for network cabling systems, e.g. in offices. They also do not utilise shielding to reduce interference.
Note: If you are running Cat5e, Cat6 or Cat6A in your home, an unshielded cable will suffice. But if you live close or are running next to power, a shielded cable is your best bet.
Higher-rated categories, such as Cat7A and Cat8, also come with shielding. They are great for achieving high frequencies.
Have your cable terminated, bonded and grounded the right way—and you can expect shielding to:
There are two common types of shielding used for cables:
Foil shielding encases a cable using a thin layer of aluminium with a polyester backing. This adds strength and ruggedness, increasing durability.
It offers 100% coverage of the conductors it surrounds. It also works in tandem with a tinned copper drain wire to ground the shield.
But the thinness makes a foil shield trickier to work with, mostly when applying a connector. Usually, the drain wire is used to terminate and ground the shield.
Braid shielding, also known as tinned copper braid, is a woven mesh of bare or tinned copper wires. It is used in conjunction with a metallic shield to ensure effective grounding.
It provides a low-resistance path and serves to complete a circuit from the shield. Then it carries unwanted electrical noise to the ground away from the circuit.
And unlike foil, it is much easier to terminate by soldering when attaching a connector. But it does not provide 100% coverage.
Depending on the tightness of the weave, braids can provide 70% – 90% of coverage. When the cable is stationary, 70% is usually enough.
Note: There is no increase in shielding effectiveness with higher coverage percentage. For one, copper has higher conductivity than aluminium.
The braid also has more bulk for conducting noise, making it more effective as a shield. But it adds size and cost to the cable. For very noisy environments, multiple shielding layers are used—both foil and braid.
In multiconductor cables, individual pairs are shielded with foil. This provides crosstalk protection between the pair. Meanwhile, the overall cable is shielded with foil, braid, or both.
When foil and braid shields are combined, each supports the other. They overcome the limitation of one with its own compensating strengths.
The shielding in cables conducts to ground any noise it has picked up. The cable shielding and its termination must provide a low-impedance path to the ground.
If it is not grounded, again, it will not work as expected. Failure to understand the implications can mean ineffective results.
Consider the following:
Suppose you want extra protection from EMI or your cable has higher frequencies. Shielded cables are your best bet. Here are some of the scenarios that can help you decide when to use one:
Check out our range of shielded data cables below:
Product code: CB-4
This 4-core shielded data cable is two pairs individually shielded with drain wire. Ideal use for computer systems and is available in 100m rolls, 305m rolls and by the metre.
Product code: CB-8
This 6-core shielded data cable 7/0.127 is sold by the metre and in quantities of 100m. Ideal use for computer systems and 100% screened cable with tinned drain wire.
Product Code: CB-1
This 8 core shielded data cable is sold by the metre and in quantities of 100m. It’s ideal for computer systems and features a tinned drain wire.
We also have the following variations – all are sold by the metre and in quantities of 100m:
Shielded cables are great against EMI in networks, particularly in industrial settings. This guide has also broken down the two common types, when to use them, and things to consider.
You should be able to get the right shielded cable for your specific needs!