Hi all,

neat topics, I like the double ball point and magnetic axis/pivot/crossed rod ideas and have included a rough sketch of a possible arrangement.

http://volcanbaru.com/OSOP/pics/crude_1_third_3_C_seismo.jpg


Using the spring would be very traditional and one of many feed back mechanism could be used.

I have always been fascinated by floating magnet things and offer this page.

http://www.instructables.com/id/Electromagnetic-Floater/

Maybe the spring could be done away with and then use the floating magnet for positioning and some finer motion sensor could be used in the feedback, maybe like Allan's

http://mysite.verizon.net/ressczez/sitebuildercontent/sitebuilderfiles/mkxi.pdf 


Use three of these arranged orthogonally at 120 degrees to derive all three components, like most modern broadband do.

Angel




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