Hi Gary,

  Why not save yourself a lot of trouble and build a short period open
loop sensor. You can apply my WQFilter.exe utility to the data and get
the equivalent of a long period sensor. See

     http://bobmcclure90.googlepages.com/winsac

---Bob

On 8/29/08, Gary Lindgren  wrote:
> My first thought after looking at all the messages from my request for input
> on vertical seismometers was to go with a mechanical concept as pictured
> http://physics.mercer.edu/hpage/new-z.html and then go with a Chapman magnet
> and coil for the pickup. But after reading more about the Force Feedback and
> the Fully-differential capacitive-array displacement sensor, I think I have
> changed my mind. I would like to end up with the Force-feedback design. I
> can see 6 months to a year of experiments to get everything going right. I
> have one question, if I have 8 to 10 Kg of mass on the pendulum, I would
> think I'm going to need quite a amplifier-driver to keep the pendulum
> stationery during events. There is also the "soft" force feedback method
> that allows a little movement of the pendulum. What are your thoughts for
> all those that are using the force-feedback method.
>
> Gary
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> Gary Lindgren
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> 585 Lincoln Ave
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> Palo Alto CA 94301
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> 650-326-0655
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>   www.blue-eagle-technologies.com
>
>   cymonsplace.blogspot.com
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