Thank you very much Bob. I will definitely look into it. I am also 
anxious to take a look at Chris's own "extender" circuit if he can 
locate it and scan it for me. I really would like to see some of these 
short period "seis" operating in a long term mode. If I need more info I 
will get back to you.  Thanks again Bob.  Ed. (edwianni1@.............

On 9/21/2012 8:45 AM, Bob Smither wrote:
> 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,
>

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