Understanding Optical Coverage in EMI Shielding Effectiveness

Optical coverage is a key metric in electromagnetic interference (EMI) shielding, representing the density of conductive material across the shield's surface area. It is typically expressed as a percentage. In braided or woven shields, optical coverage measures the amount of open space between the conductive wires or strands, indicating how effectively the shield blocks EMI.

The Technical Definition of Optical Coverage

In braided cable shielding, optical coverage is determined by the weave structure and fill factor. The fill factor is calculated based on the braid’s weave angle, wire diameter, and the spacing between wires. This percentage reflects the "solidness" of the shield. Higher percentages (closer to 100%) indicate denser coverage and better EMI protection.

• Higher optical coverage generally offers better shielding, though it can also impact flexibility and weight.
• For example, a shield with 95% optical coverage will have fewer open spaces, leading to higher shielding effectiveness. This dense weave is better at reflecting and absorbing electromagnetic waves, thus protecting sensitive electronic components from interference.

However, achieving very high optical coverage requires careful design and material choices, especially when flexibility and weight are important considerations.

Zippertubing's Approach: Testing Across Frequencies

While optical coverage is important, it does not provide a complete picture of a shield’s performance across the electromagnetic spectrum. Zippertubing takes a more comprehensive approach by conducting shielding effectiveness (SE) testing across a range of frequencies. This testing allows Zippertubing to evaluate how well their shielding products attenuate EMI across diverse frequencies, which is crucial for industries such as aerospace, defense, and telecommunications.

By combining high optical coverage with rigorous SE testing, Zippertubing ensures that their shielding products provide reliable EMI protection tailored to real-world conditions.

Why Optical Coverage Matters

Optical coverage serves as an essential baseline for assessing shielding quality, but testing across frequencies provides a more complete understanding of how the shield will perform under various conditions. For applications where sensitive equipment is critical—such as aerospace or medical technology—Zippertubing’s EMI shielding solutions offer both high optical coverage and proven performance across the frequency spectrum, delivering adaptable and reliable protection for critical systems.

Contact our in-house engineers to learn more!