The results can range from temporary disturbances and data losses to system failure and even loss of life. For engineers, it's important to recognize how electromagnetic energy EME in the application environment can cause interference.
Without this basic EMI awareness , you may design gaskets that lack adequate protection against electromagnetic fields in the radio frequency RF spectrum, the part of the electromagnetic spectrum with frequencies from 3 kHz to GHz. RF waves form the basis of radio technology, but they can also transmit signals that interfere with wireless communications. Railroad and mass transit systems , medical equipment , and military applications also face their own specific challenges.
Increasingly, intentional electromagnetic interference IEMI also represents a threat to non-military assets such as the power grid and other types of critical infrastructure. Railroad and mass transit systems may experience EMI because of application-specific factors such as:. Medical equipment is susceptible to EMI, too.
Application-specific sources include:. Some of these threats are extreme, of course, but all engineers need to assess EMI risks in order to incorporate appropriate protection into their gasket designs. Our EMI shielding and thermal interface material portfolios are designed to give customers the ultimate in design flexibility. An EMI shielding gasket is a mechanical device that helps protect electronics from electromagnetic interference.
Traditionally, EMI shielding has been fabricated from metal sheets and formed into shapes that fit electronic housings or enclosures. Aluminum, copper, and steel are strong and rigid, but thin metal sheets can deform under the pressures that are required for sealing.
However, it may add to the cost and footprint of the cable. The copper shielded cables are ideal for industrial environments. Metal-coated Mylar and Foil Shielded Cables : Foil shielded cables feature a thin sheet of aluminum or copper which is bonded to polyester to improve the cable strength. The foil shielded cables are a common choice for noisy retail or busy office environments. Multiple shielding layers may be used for extremely noisy environments.
In such environments, braided and foil shielded cables are used together. Some applications use multi-conductor cables where both types of shielding are commonly visible. In such cables, sometimes individual pairs are foil shielded, whereas the overall cable is braided or foil shielded.
The foil shielding of individual pairs help avoid crosstalk that may occur between different pairs in a cable. The following points will help you understand it better:. Shielded Cables : Electromagnetic interference or EMI is one of the most common phenomena on the factory floor. EMI is a term used to define electrical noise that is usually conducted or radiated.
This is done to prevent crosstalk between pairs. Besides the braid covering, the maximum admissible diameter of the single strand of braid and the angle of twist to the axial axis of the conductor are also determined in the manufacturing. The thinner the single strand and the smaller the angle of twist, the more flexible is the cable. However, the diameter of the single wire is restricted due to the mechanical requirements. A cable shield consists of a respective amount of strands, depending on the braiding machine 16, 24, The total amount of strands equals the number of strands in a braiding element times the amount of elements.
The strand diameter, the angle of twist and the folding number also determine the density of a shield. The single strands are combined to make larger strands.
The larger strands are then unwound from the coils and are mounted on special braiding machines for stranding construction around the conductors.
Connecting shielded cables As noted above, certain designs accommodate crimping or soldering of connectors easier than others. A braid can be manufactured using a wide variety of materials and wire sizes and can be applied over an extensive range of cable diameters. A spiral shield is made of conductive wire helically wrapped over the core. As with a braid, a variety of materials and wire sizes can be used, however, spiral shields are generally limited to small or mid-sized cables in order to achieve high coverage.
A foil shield is a metallic foil helically wrapped around the cable with overlap. A variety of foil options can be utilized, however, most common is aluminum laminated with a polyester backing.
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