Geoffrey M. Voeth wrote:
> I'm Not Trying to be a smartass but,
> ShaZam ??? !!!
> 
> Is there any way to make the magnetic thing be linear
> like possibly using a Hall effect sensor an electro magnet and a pid loop
> like a automobile speed control ?
> 
> I am possibly thinking of using magnetic repulsion/attraction  to
> reduce the pull of gravity and thus increase the
> period of a vertical geophone ?
> 
> You need an acceleration in the opposite direction
> not quite as powerful as the Earths ?
> Does not matter what causes the acceleration in
> the opposite direction (UP) ?
> 
> Any ideas in how to do such a thing ?
> 
> Regards,
> geoff

Hi Geoff

With the understanding that I may be wrong, I will comment.  The 
geophones that I am familiar with have a suspended coil arranged to cut 
the lines of a fixed (to the case) permanent magnet.  Adding an external 
magnetic field might increase or decrease the sensitivity (Volts / m / 
sec) but I don't see how it could change the period.  AFAIK the 
suspended coil form is non-magnetic.

Regards,

Bob