The Importance of Shielded and Unshielded Cables in Modern Infrastructure

As technology rapidly evolves, companies are continually upgrading their infrastructure. It is essential to understand the various types of cables and their requirements to ensure the efficient operation of your systems. One of the key aspects of maintaining smooth functionality is the proper use of shielded and unshielded cables.

Electromagnetic Interference (EMI) in Industrial Applications

Industrial settings, such as factory floors, are often electrically noisy environments. Electrical noise, whether radiated or conducted as electromagnetic interference (EMI), can severely disrupt the proper operation of other equipment. While insulation protects cables from mechanical damage and environmental factors such as moisture or spills, it does not shield against electromagnetic energy. This is where shielding becomes crucial.

Cables can both emit and receive EMI. As a source, cables can either transmit noise to nearby equipment or act as antennas radiating the noise. As receivers, they can pick up EMI from other sources. A shield is essential for mitigating the effects of EMI in both cases.

The Role of Shielding in Cables

Shielding is needed to protect cables from EMI, and certain industrial applications present high levels of both conducted and radiated EMI. For instance, large transformers, switching heavy loads, and inductive heaters can generate significant interference. Placing signal cables next to power cables can also result in noise coupling onto the signal lines.

What Are Shielded Cables?

Shielded cables are constructed with insulated conductors enclosed in a conductive layer. This shield can be made from materials like braided copper wire, spiral copper tape, or conductive polymers. The significance of shielded cables cannot be overstated.

Typically thicker and stiffer than unshielded cables, shielded cables require careful handling. They are commonly used in industrial settings where nearby equipment could generate EMI.

Shielded Cables

Types of Cable Shields:

Combination Shields

Foil Shields

Metallic Braid Shields

Spiral Shields

Serve Shields

Tape Shields

Applications of Shielded Cables

Shielded cables are crucial for protecting data transmitted over cables in environments with high electromagnetic interference. These environments may include data centers, industrial facilities, offices, and other areas that rely heavily on computers, electrical equipment, or electronic devices.

When to Use Unshielded Cables？

Unshielded cables do not have a protective shield to minimize interference. They are commonly used in office networks and similar cabling systems. While they are more susceptible to interference, unshielded cables remain popular due to their:

Versatility

Cost-effectiveness

Ease of installation

Lightweight design

Flexibility

Guide to Effective Cable Shielding

To ensure your cables are adequately shielded for your specific application, follow these guidelines:

In moderately noisy environments, a metal foil shield will usually provide sufficient protection. In areas with high levels of interference, consider using a braid or a foil-braid combination.

Choose the right type of cable for your needs. For cables that require frequent bending, a spiral-wound shield is more suitable than a braid.

Avoid using pure aluminum foil shields on flexible cables, as constant bending can tear the foil.

Make sure the equipment connected to the cable is properly grounded. Use earthing points wherever possible and ensure the connection between the earthing point and the equipment is secure. A low-resistance ground path is essential for reducing noise.

Most connectors allow the shield to be terminated 360°, but ensure that the connector's shielding effectiveness matches that of the cable. For example, many connectors feature metal-coated plastic or cast zinc/aluminum backshells.

Avoid over-specifying connectors, which can lead to unnecessary costs, or under-specifying them, which could result in insufficient shielding.

Ground one end of the cable to eliminate ground loops, which can introduce noise.

Remember that a shielding system is only as strong as its weakest component. Poor-quality connectors can degrade the performance of high-quality cables, while good connectors won’t improve poor cables.

By adhering to these practices, you can ensure optimal performance and minimize the risks posed by EMI in your infrastructure.