shield effectiveness chart

Shield the Noise

Posted on Wednesday, June 3, 2015 by Kimberly Versaw

The shielding of electronic interconnect cables can play a critical role in overall system performance.  System configuration, type of signals transmitted and proximity to noise generating sources all must be considered.  These factors plus the type of interference, whether electromagnetic, electrostatic discharge (ESD) or radio frequency, will determine the necessity and type of shielding required.  Alpha’s Xtra-Guard cables are available in an advanced braid/shield construction known as SupraShield®.  Alpha’s premium SupraShield cables combine a triple-layer aluminum/polyester/aluminum foil with a tinned copper braid shield with tight 70% coverage. SupraShield offers exceptional EMI performance and flexibility to protect against noise and maintain overall system integrity. The combination of foil and braid offers better shielding effectiveness than either approach alone against both low- and high-frequency noise.

Let’s go over the importance of a braid shield for when it comes to shielded coverage.  The effectiveness of a braided shield depends upon the percent coverage afforded by the shield. Leakage in a braided shield is due to air spaces which exist between the weave. The following equation can be used to determine the percent coverage of a braided shield.

shield coverage equation

The D.C. resistance for braided shields can be calculated using the following equation:

shield resistance equation

Now that we know how to calculate the necessary coverage needed for shielding our cables, our next blog will discuss the Xtra-Guard line of cable and its shielding options.


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