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Faraday cage, shielding and grounding

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ricko_uk:

Between copper mesh and stainless steel mesh, considering the mechanical sizes are the same, which provides best electric and electromagnetic protection?

Thank you :)

rhb:
I'd expect copper mesh to perform better, but I've never seen data to confirm that. I doubt that there would be significant magnetic field benefit from SS mesh.

Low carbon steel as used for making galvanized sheet for HVAC duct work has fairly high permeability.  I doubt that the permeability of stainless steel would provide much shielding even as sheet.  Much less as mesh.  Work hardening requires annealing after forming for best performance.  At the price of mumetal, pretty much required to justify the expense.

A bit of context as to the  scale of enclosure you want to build would be very helpful.  Along with purpose.  Metrology requirements are very different from RF testing.

I'm doing both RF and metrology, so I'll have a shielded room  with shielded test chambers for metrology experiments.  And size and budget  matters.  For cheap I'd cover things with aluminum foil with 4" wide aluminum foil duct tape on the seams.  The capacitance per square inch is so large that it's a dead short at RF. 

If I were building a lab in a rented apartment, I'd staple aluminum foil to the walls, floor and ceiling, cover the seams with foil HVAC tape, solder a wire to a strip of wide copper foil tape and apply that to the aluminum to capacitively couple the foil to ground.  Then lay a sheet of cheap vinyl flooring over the foil on the floor.  ESD flooring is about $6/ft.  Even a few square feet would cost more than the rest of the room treatment.

Galvanized steel sheet is less than 1/2 the cost of copper screen.  So I can't see using copper screen unless you need the airflow.  I plan to use galvanized duct filled with copper scrubbers for the air supply to my room with muffin fans on the outside of the room.

Reg

RandallMcRee:

--- Quote ---There are two issues:  electric field and magnetic field.  Copper will not block magnetic fields whereas low carbon steel sheet is fairly effective above 1 MHz.  Screen drops in effectiveness as the frequency goes up. Low frequency magnetic fields require mumetal which is quite expensive as it is nearly pure nickel.  Galvanized steel sheet is a good enough conductor to be effective for the electric field.
--- End quote ---

Yes, but...
Having done extensive modeling in FEMM* I always found mu-metal to be very expensive compared to steel and never better except if weight is the most important thing, e.g. you're going into outer space (satellites) or you're the military.
Otherwise you can just keep making your steel thicker or at worst use two separated steel sheets. Anyway, that's what FEMM says.

* http://www.femm.info/wiki/HomePage

rhb:
Amen

ricko_uk:
Thank you all :)

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