# Cancel out Earth's Magnetic field

Is there any tools except helmholtz coil to cancel out earth's magnetic field to calibrate magnetometers in practice.

• Well, you could build a more complicated coil if you really wanted to, but it would be a pretty silly thing to do unless a Helmholtz coil is failing you for some fundamental reason. – dmckee Apr 24 '13 at 20:29
• Thanks @dmckee ! Helmholtz coil is my term paper topic. I just want to know that if there any. – ecabuk Apr 24 '13 at 20:33
• I am not ware of any other named coil configurations for that purpose because the one Helmholtz found is perfectly adequate. It is not, however, unique. – dmckee Apr 24 '13 at 20:39
• A box made of thick iron plates maybe. However that iron could become magnetized and then the box might produce an internal field instead of cancelling it.. – SpiderPig Apr 24 '13 at 21:29
• @Eduardo: No, a Faraday cage is for shielding electric fields, not magnetic fields. It will attenuate changing magnetic fields somewhat because those will cause currents in the cage, which causes some of the energy to dissipate. Since the cage does not have zero resistivity, the currents caused by the magnetic change will decay and the net static magnetic field will go right thru the cage. – Olin Lathrop Apr 24 '13 at 23:22

David H provided a good answer, but the short answer to your question is "yes", other shielding (passive) exists. A Mu-Metal ($\mu {-metal}$) has a very high magnetic permeability and can be used to provide magnetic shielding. Some call these "Zero gauss chambers". These essentially "channel" the magnetic field around the center of the chamber.