Thanks All,

I think i found the right combination.

The formulas I used are on my website at

Circuitry and Formulas:
http://gmvoeth.home.mchsi.com/circuit/Circuit.HTML

Current-Seismicity:
http://gmvoeth.home.mchsi.com/realtime/realtime.html

I did allow for mechanical damping which seems about h=0.033
but I did not find the specs for my exact geophone.

It is amazing how much difference a small change with Rdamp can make.

It seems to me Jon told me sometime ago Rdamp is about 3X Rgeo
Which makes R total = 4X Rgeo.
This seems to work out right with the numbers.

My webpages may be unconventional.
If you can see them that's all i expect
since I'm no expert in anything.
I have had a problem with cases where
the webpages work OK on my machine
but not from the server on the internet.
Sometimes I use other webpages found wherever
as models to what to do.
The most generic is what i like to use.

Regards,
geoff

On 2/6/2012 12:42 AM, chrisatupw@....... wrote:
> 
> Subject: Damping Resistor
> 
> Is anyone able to comment on this expression
> o get a value for the damping resistor ?
> Hi Geoff,
>     Most geophones use a copper coil former, which also forms part of 
> the mass. Since this is moving in the magnetic field, damping currents 
> are induced in it, giving maybe 0.4 critical damping. I think that your 
> formula relates to a system with no inherent damping. The manufacturers 
> supply response curves for a range of damping resistors.  
>     Regards,
>     Chris
> 
> 
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