Positive Faraday Cage

Thread Starter

Atenuator

Joined Jun 22, 2012
8
Hello, I am trying to block or redirect a strong magnetic field. I was successful for a while with building a makeshift faraday cage and grounding it. Now it appears the ground I was using has been biased, so the cage no longer functions. I was wondering if I could positive bias the cage by connecting to the positive post of a car battery to make the cage effective against the magnetic field.

Thanks
 

Thread Starter

Atenuator

Joined Jun 22, 2012
8
the cage worked perfectly while I had a source of true or pure ground, with just aluminum and copper for the cage. I was thinking that because the ground attracted the electrons from the mag' field, that a positive potentialed cage might do the same.
 

nsaspook

Joined Aug 27, 2009
6,933
the cage worked perfectly while I had a source of true or pure ground, with just aluminum and copper for the cage. I was thinking that because the ground attracted the electrons from the mag' field, that a positive potentialed cage might do the same.
Is this a static magnetic field or if it's not, what frequency?

Typical Faraday shielding requirements.
 

bertus

Joined Apr 5, 2008
20,319
Hello,

MRI uses a static magnetic field for the main coil.
Inside the main coil there are gradient coils wich are pulsed to make the image.
The Z-gradient is is line with the main coil.
You will likely not notice the gradient pulses outside of the MRI magnet.
You can hear the gradient pulses as ticking and buzzing, so they must be in the audible range.

Bertus
 

sailorjoe

Joined Jun 4, 2013
361
You can get an explanation of Helmholtz coils on Wikipedia. In that article there is also a photo of a three axis Helmholtz coil arrangement around an electron microscope. After that, just google "Helmholtz coil" and you'll see things you can buy.
 

Thread Starter

Atenuator

Joined Jun 22, 2012
8
You can get an explanation of Helmholtz coils on Wikipedia. In that article there is also a photo of a three axis Helmholtz coil arrangement around an electron microscope. After that, just google "Helmholtz coil" and you'll see things you can buy.
Thank you.
 

Kermit2

Joined Feb 5, 2010
4,163
Building the small coil structures and getting the power supplies to energize them is not the problem. Getting good reliable readings of the magnetic field inside and periodic calibration to maintain field cancellation settings
Doing it is easy, doing it right is the hard part
 
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