Cable shielding density is a quantitative indicator of the shielding ability of a cable shield against electromagnetic signals. It is usually expressed as a percentage, reflecting the degree to which the shield can block or attenuate electromagnetic interference. For example, in the case of a braided shield, the shielding density depends on factors such as the thickness of the braided wires and the tightness of the weave. A higher braid density means smaller gaps between the braided wires, and thus a stronger ability to block electromagnetic interference. For example, a shielding density of 90% means that the cable shield can theoretically block 90% of external electromagnetic interference signals, allowing only 10% of interference signals to pass through the shield and affect signal transmission within the cable.
Common cable shielding densities vary. The following are some of the more common ones:
• 70%: Provides a certain degree of protection against external electromagnetic interference and is suitable for general electrical equipment connections with relatively low electromagnetic shielding requirements.
• 80%: Provides good electromagnetic interference suppression and is commonly used for internal wiring of general electronic equipment and office equipment.
• 90%: Provides excellent shielding effectiveness and is suitable for applications with certain electromagnetic environment requirements, such as industrial automation control systems. • 95%: Offers high shielding performance and is commonly used in cables sensitive to electromagnetic interference, such as communications and data transmission.
• 98%: High shielding density, suitable for specialized applications with stringent electromagnetic shielding requirements, such as medical equipment and aerospace.
• 99% and above: Provides extremely excellent shielding effectiveness and is generally used in military, high-end scientific research, and other applications with extremely high electromagnetic compatibility requirements.
The selection of cable shield braid density requires comprehensive consideration of multiple factors, including the application scenario, equipment requirements, and cost.
Chinese standards have different requirements for cable shielding density:
• For single-core shielded cables with a nominal cross-section of 0.12 mm² or less, the shield braid density should be no less than 60%.
• For other shielded cables, the shielding density should be no less than 80%.
• For computer cables: The individual shielding density must reach 85%, and the total shielding density must reach 95%.
• For control cables: When using round copper wire braided shielding, the braid density should be no less than 80%.
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