Cable assemblies are utilized in a variety of industrial applications, which can exhibit electrical noise. Electrical noise can lead to Electromagnetic Interference (EMI) in cable assemblies. When a cable assembly receives or generates electromagnetic interference, it can cause poor signal quality and loss of data. It can also disrupt the function of electronic equipment and other components around it. Hence, it is necessary to use special shielding to protect cable assemblies from EMI.
Shielding for Protecting Cable Assemblies from EMI
Cable shielding is used to resolve the issue of EMI in cable assemblies. A cable shield encapsulates the conductor within the cable to provide effective protection. The shielding impacts EMI in two ways.
- The first way is by reflecting the electromagnetic energy.
- The second way is by picking up noise, and grounding it.
Although some energy will pass through the shielding, but it will be so highly attenuated that it won’t have any impact on the assembly.
Types of Shields Used In Cable Assemblies
Various types of shields are used in cable assemblies based on the application they will be used in. Commonly used shields in cable assemblies are:
- Foil Sheaths: Foil shields comprise a thin layer of aluminum or copper attached to a carrier such as a polyester or Polypropylene film. A foil sheath provides 100% coverage to the cable or components. The foil shield consists of a drain wire for terminating and grounding the EMI.
- Metal Braids: A braid shield is constructed as a woven mesh around the cable core. It is constructed from bare or tinned copper wires. For special applications, stainless steel or silver plated copper braid construction is also used. Metallic braids provide improved termination and lower DC resistance than foil sheaths, which makes them ideal for low frequency interference.
A cable assembly needs to have appropriate shielding according to the application it will be used in. However, it is also important that the equipment connected using the cable assembly should be properly grounded.