John,

The electronics need for a Lehman is pretty straight forward. After the
pickup coil, I use a 220 volt AC relay coil, you will need an amplifier,
maybe a low-pass filter and some way too display the information. This can
be a chart recorder or a computer with an A/D card and software. If you use
a chart recorder the low-pass filter probably isn't needed. If you use a
computer and A/D card you should have a low-pass filter between the Amp and
the A/D card. 

For a schematic of an Amp / Filter board see
http://www.seismicnet.com/eqampd.gif. If you don't want to make your own,
check out http://www.seismicnet.com/eqamp.html. I also have an A/D card and
software if you want to go that route. See
http://www.seismicnet.com/atod.html for more info.

Regards,
Larry Cochrane
Redwood City, PSN



At 01:23 PM 6/6/00 -0500, you wrote:
>All,
>
>I would like to know if anyone has available schematic diagrams for the
Lehman seismograph construction.  I understand a great deal of the
mechanics for such an instrument however my knowledge of electrical systems
and components is limited to the benefits of light switches and the like!
>
>I have CAD capabilities (microstation or AutoCAD) so if electronic files
are available I would appreciate it if they could be forwarded.  If hard
copies are available I will send a SASE and gladly pay for any reproduction
cost. 
>
>Thank you.
>
>Regards,
>John Finke, P.E., S.E.
>finkeje@............

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