On Sun, 2012-09-16 at 19:53 -0400, Edward Ianni wrote:
> Hi all:
>           I have two very old seismometers and I would like to extend 
> their "periods", electronically and EXTERNALLY if that is possible. I 
> tried this a long time ago but I am not heavy into electronics and could 
> not come up with the right values for some of the circuits that I looked 
> at. The two Seismometers are a Kinemetric SH1 "Intermediate"(about 5 
> second period), and a Sprengnether (square box type) with a 1.5 second 
> period. Is it possible to do this easily and is there a circuit 
> somewhere with relatively simple instructions for calculating component 
> values? Thank You.  Ed.

Hi Ed,

Besides the inverse filtering method that others have mentioned you
might consider the Lippmann approach.  In brief this involves loading
the seismometer with a negative resistance to greatly overdamp it.  The
technique is used in the Lennartz seismometers.  A Google search for
"lippmann seismometer or 'lippmann geophone' will turn up lots of
information.

Let me know if you need any more information.

Regards,

-- 
Bob Smither                             bob@...........
=======================================================
History, n: An account mostly false, of events mostly
  unimportant, which are brought about by rulers mostly
  knaves, and soldiers mostly fools.
    -AMBROSE BIERCE  The Devil's Dictionary (1906)
=======================================================

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