mu-metal

[thedug]

Anybody know where to get small quantities of mu-metal on the cheap?

 

[VacuumVoodoo]

http://www.lessemf.com

Wide choice of mu-material, quick delivery.

 

[alk509]

[quote author="VacuumVoodoo"]http://www.lessemf.com[/quote]

:shock:

Holy Jeebus! That **** is expensive!!! I mean, I knew it wasn't cheap, but DAMN!

Peace,
Al.

 

[asm]

stupid question.... but can you line regular metal with copper foil like they do on guitar control cavaties to help the shielding.

its cheap and easy, doesnt look as good but i've never seen someone do it on a rackmount gear. wonder why?

taylor

 

[jensenmann]

this guitarshielding technique (alu, copper, graphite) doesn´t work at lower frequecies (for example 50Hz hum). Therefor you need mumetal (or copper of 10mm thickness :wink: ).
Jens

 

[asm]

gotcha.

10mm copper sheet is WAY cheaper than that though :?

www.onlinemetals.com

 

[NewYorkDave]

It has a lot to do with the mechanism of coupling. Copper makes an excellent electrostatic shield, but it is useless at preventing magnetic coupling. Can you pick up a (US) penny with a magnet? Nope.

If mu-metal is too expensive, a couple of nested layers (separated by a gap) of steel shielding may do an acceptable job. But you'll end up with a package that's a lot bigger, for a given amount of effective attenuation, than if you'd used mu-metal.

High-quality input transformers use a combination of magnetic (e.g., mu-metal) and electrostatic (e.g., copper) shielding.

 

[bcarso]

A really good reference for shielding, both how and why, can be found in Peter Fish's Electronic Noise and Low Noise Design (Macmillan Press Ltd. 1993, McGraw-Hill 1994).

I have never seen as good an explanation of things like how a.c. mag fields in the near field region fall off as the 3rd power of distance, and other issues. Excellent mix of theory and practice.

 

[CJ]

Remember, if you bend mu metal, it loses it's shielding properties. So you need to aneal it after you bend the housing. Induction heating or hydrogen oven.

 

[Guest]

heh thats a cool site , bahaha :

SILVER LINING GARMENTS
Gain Control of Your Inner Environment

Very sheer, comfortable undergarments you can wear over your regular underwear to shield yourself from powerline and computer electric fields


mu-metal short~es

 

[Guest]

if i have a piece of gear that has a cheap transformer that induces noise into other gear, woudl it be reasonable to use some of this foil to shield surrounding equipment?

if you bend mu metal, does it become inneffective? or just reduced effectiveness?

 

[CJ]

It's kind of like a magnet, only reverse. If you drop a magnet, it will lose some of it's magnetism. If you bend mu metal. it will lose it's abillity to shield magnetism. I do not know how much damage the bending causes. Maybe ask Ollie at Tab/Funkenwerk. He makes his own cans.

 

[gyraf]

In my experience, mu-metal shielding is preserved quite good as long as you don't make sharp bends. With a bend diameter of say 5mm, I don't get bad results at all when shielding inductors and transformers. But who knows how good it COULD have been.. :grin:

Jakob E.

 

[Dan Kennedy]

I make little cups out of cut and bent mu metal all the time. I don't bother annealing them.

I buy it in a semi-annealed form. If anyone wants small samples to play with, I have some scrap pieces.

 

[bcarso]

One thing about mu metal---it is VERY hazardous to handle, especially after cutting with tin snips. No matter how good you think you are, try to get some good heavy gloves and use them.

 

[alk509]

[quote author="bcarso"]One thing about mu metal---it is VERY hazardous to handle[/quote]

Excuse my ignorance, Brad, but what exactly do you mean? Is it wicked sharp?

Is it toxic??? :shock:

Peace,
Al.

 

[bcarso]

Wicked sharp.

Also, apparently it is really good for harboring biologicals on the surface for some weird reason. A friend of mine got a cut with it and the blood poisoning damn near killed him. But maybe that was an anomaly.

Brad

 

[kevinc]

Get an old Tektronix vacuum tube oscilloscope that is a basket case already and salvage the CRT shield. The shields aren't too thin, so may be a challenge to bend, but they are cheap!

 

[Guest]

here is a page with some good information. they also sell mu metal foil that can be shaped at home.

http://www.magnetic-shield.com/