EMI shielding question

Feb 07, 2007 4 Replies

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Michael 19 years ago

How effective is mildly conductive material when it is used as a shield? ? The frequency range of interest is ~100kHz and up, probably way in the GHz range (SMPS, and spark discharge) The material is graphite-filled (40%) Ryton. Multimeter shows between tens and hundreds of kOhms between probes placed few inches apart, depending how hard I push the probes. I have really nasty noise source (switcher and aprk discharge) approximately 1/2" away from sensitive electronics which is inside of the housing made of the material in question. Silver coating would be a logistical nightmare.... Bilding copper housing is am option, but still a PITA.

Can anybody refer me to an information source?

THANKS!! Michael

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Michael 19 years ago

The problem is that exact volume resistivity of the material (40% carbon) is not known (proprietary issues?)

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John Popelish 19 years ago

I think you will be badly disappointed by the Ryton. Look up the penetration depth formula for EM waves versus volume conductivity. I think you will need an actual formed metal container that has good seam conductivity and small holes.

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Wimpie 19 years ago

Hello Michael,

I do not think that it is going to work. You will have some shielding for low frequency E-field (when you ground it), but for your application where you have strong varying electric and magnetic fields you will need metal (reflective attenuation).

The thickness and mounting will depend on the required attenuation.

Best Regards,

Wim PA3DJS

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jpopelish 19 years ago

Here is an article that covers many of the concepts of effective shielding:

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