[time-nuts] Cheap Rubidium

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Dec 24 21:58:40 UTC 2009


You have to be careful with random junkyard steel, not all of it is 
necessarily that magnetic as I once found when testing steel tube in a 
workshop.

One can test this with a magnet.

Mu metal saturates very easily and sometimes its necessary to reduce the 
magnetic field using a higher saturation lower permeability material 
first before using mu metal inside the outer shield.

Mu metal readily loses its shielding ability if bent or worked in any way.
Post fabrication annealing is usually required.
Dropping it, bending it or hitting it with a hammer can be sufficient to 
negate its shielding effectiveness.
Adhesive backed thin foils can be easier to use:
http://www.advancemag.com

Hal Murray wrote:
>    
>> If I had a bunch of mu metal sitting in the basement I'd certainly use
>> it in the setup. Last time I checked the stuff was not cheap ....
>>      
> How good is mu metal relative to typical steel?
>
> I'm interested in shielding/$.  If I have $X to spend on shielding (for a
> hobby project), am I better off spending it on mu metal or junk yard steel?
>
> In this case, space or weight is not a significant disadvantage.  (If I can
> also use it as a thermal layer, it might even be an advantage.)
>
> ------------
> 			
> Years ago, I was helping	 somebody with two displays.  They were interacting with each other in unpleasant ways.  We tried some thin mu metal.  It didn't help much.  A big chunk of 1/8 or 1/4 steel worked much better.
>
>
> htt
>    






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