I read this with much care and after some investigation I now understand Mumetal cans work not by diverting magnetic fields but by shunting them.... (to GND ?!)
Is it necessary to connect a mumetal cage to gnd in order to work properly ?
I have been experimenting with iron versus aluminium lids and found that a layer of iron near the magnetic source covered by another (alu) is better than the reverse (alu near the tx and iron on top). The gains are evident even without connecting the lids to gnd.
In the case of mumetal, can I expect a similar behaviour ?
Regards
Ricardo
Is it necessary to connect a mumetal cage to gnd in order to work properly ?
I have been experimenting with iron versus aluminium lids and found that a layer of iron near the magnetic source covered by another (alu) is better than the reverse (alu near the tx and iron on top). The gains are evident even without connecting the lids to gnd.
In the case of mumetal, can I expect a similar behaviour ?
Regards
Ricardo
My best results are obtained with the plates connected to GND but I also get very good results just by covering the circuit with an iron plate.
I have read that severall thin plates work better than a thick one... these should be placed with a dielectric between them (air).... In this case I should connect all plates to gnd right ?
I have read that severall thin plates work better than a thick one... these should be placed with a dielectric between them (air).... In this case I should connect all plates to gnd right ?
love the ZERO link! thats excellent. contemplating getting some of the mini enclosures and the deepdrawn cans. the mini flanged mumetal lids could be designed into a PCB with the mounting holes and grounding pads to cover a dac chip. I know the gains are unlikely to justify the means, but hell if nothing else it'll look sweet 
The problem with wrapping things in sheet, or indeed making a DIY can from mumetal sheet, is that the permeability of mumetal drops massively after mechanical work. For high performance use, it is first made into the target shape, then given a special annealing cycle under a hydrogen atmosphere to restore the magnetic properties.
This is why decent shielding cans are so expensive. I used to work in a physics lab, and had mumetal shields for one of my experiments; they were very effective, but cost over £1000 - say $1500.
Second hand or surplus cans may be your best bet.
I know that Sowter transformers offer shielding options on some of their transformers, and will sell you empty cans.
This is why decent shielding cans are so expensive. I used to work in a physics lab, and had mumetal shields for one of my experiments; they were very effective, but cost over £1000 - say $1500.
Second hand or surplus cans may be your best bet.
I know that Sowter transformers offer shielding options on some of their transformers, and will sell you empty cans.
low carbon steel/iron is cheap so you can use lots, heavy sections, air spaced layers and get good mag field attenuation practically and much cheaper than with exotics like mu metal
also you need to think of mag shielding as diverting the field - Fe is 100s-1000s of times more permeable than air so the mag field wants to "shortcut" through the iron
you could even use cast iron plumbing pipe fittings to make up shielding cans for small xfmrs - just don't try to take them on airplanes
also you need to think of mag shielding as diverting the field - Fe is 100s-1000s of times more permeable than air so the mag field wants to "shortcut" through the iron
you could even use cast iron plumbing pipe fittings to make up shielding cans for small xfmrs - just don't try to take them on airplanes
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