There is an ASTM (I do not recall the number) for just your purpose. The jig is an expanded piece of coax, with a slot into which a puck of the test material may be inserted. If the material is a perfect conductor, it shorts the input and you get no output. If the material is a perfect insulator, you get 100% transmission. In between, you can relate the percent transmission to SE (dB). I bet someone reading this knows the number and can cite a source for the jig. The jig and technique were developed at NBS (now NIST).
Note that this is purely a measure of far field SE. Ken Javor ---------- >From: Antonio Cinquino <[email protected]> >To: [email protected] >Subject: Impedance & Shielding Eff. >Date: Wed, Jan 17, 2001, 11:27 AM > > > Dear Group, > > I have a task assigned and I don't know where to begin. I'll be > as descriptive as I can and look forward to hearing your > comments/suggestions. > > Within our company it has been suggested that the fiberglass > body that acts as a structural support (a sort of canopy) be impregnated > with copper mesh to give it shielding properties. It will be used to > provide extended shielding of some electronics inside. My question is with > regards to determining the following: > > > 1) the shielding effectiveness (near and far field) > > 2) Impedance over frequency (up to 500Mhz) (I've seen several plots of > impedance over frequency for "grounding straps" and "system reference > potential planes", does anyone know how these plots are formed, measurement > or calculation?) > > > What has been put on my desk is several pieces of fiber glass about > 1ftx1ft. One has the wire mesh impregnated, one has a conductive coating, > the other has, i think a mixture of the two, (by the way the overall > structure of the final product will be irregular and fairly large) Can any > one suggest to me a quick test jig that I can setup to help determine the > above two points (using the 1ftx1ft fiber glass and required measurement > equipment). This would help determine which of the three fiberglass pieces > is best. > > I'm not sure what this question might sound like to the rest of you. > I guess I'll figure it out from the responses :) > > Thanx in Advance > > Best Regards, > > > > > > > > Antonio L. Cinquino > CAE Electronics Ltd. > Electrical System Designer > > Phone : (514) 341-2000 (ext. 4303) > Fax : (514) 340-5552 > Pager : (514) 897-5166 > > Email : <mailto:[email protected]> [email protected] > > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
