I was just thinking if you can adjust the geophone up or down a bit and apply a dc bias to either levitate or drop the mass to its 
center point using a steady current source you might alter its characteristics. I am afraid to do this (makes me feel whimpy to say 
this) but I can not endanger a geophone I may never be able to replace. Possibly one or more of you can tell me what the application 
of a DC bias current to a geophone will do ??

If I can find out it will not damage the coil or magnet I may try it myself.

I used to have a 500# seismometer (compliments USGS)and discovered you can magnitize the thing yourself by pulsing a current into 
the coil so of course it is also possible to kill a magnet this way too.
I gave that seismometer to my alma mater
because you just try to keep it from wasting away
when you have no proper place to put it.
But i will tell you with certainty you will never
get a better picture with anything smaller that i know of.
I was getting all three waves with ease.
The mass was like 200 or more lbs and the spring
had a constant of like 98lbs/inch and was a ribbon like
instead of wire. I wanted to take the whole thing apart
but knew it was too much like an automobile and you really
need a crane or something to handle that mass.

Hey...I just received a nice telesismic wave while writing this.

P = 11:26:44 2006NOV22 UTC at GVA (listed wrongly as currently closed)

The time is crude derived from the screen and not analyzed properly.

Will be happy to share my text psn file if anyone interested.

Regards;
geoff


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)