Hi Bob,

I think I called it 'G' just to correspond with what's used on the 
geophone's data sheet for sensitivity.  It is indeed a VCVS.

The noise runs I have done on one of Dave's circuits, show noise 
levels far below what I would expect.  I am assuming the noise 
parameters for the AD706.  I think there's an error somewhere.

I uploaded a noise plot.  The noise is referred to the model input, 
that is, equivalent ground noise.  Units are m/sec/sqrt-Hz
http://bnordgren.org/seismo/NoisePlot.jpg

Brett

At 07:38 AM 10/9/2012, you wrote:

>On Tue, 2012-10-09 at 05:52 +0100, Malte Ibs-von Seht wrote:
> > Hi Brett,
> >
> >
> > what kind of component is the one labelled "Gv 28.8" in your SPICE
> > model?
>
>In SPICE notation it would be a voltage controlled current source (G
>element - transconductance). According to the model the input to Ceqv
>should be a voltage representing velocity.  I believe that Brett meant
>that to be a SPICE E element - a voltage controlled voltage source.  The
>28.8 would be the gain (geophone generator constant) representing the
>28.8 Volts / m / sec response of the PS-4.5B phone.  The one volt source
>then represents 1.0 m / sec velocity input.
>
>In the example I posted earlier using CCICAP (See:
>http://c-c-i.com/2.95171615931122/ ) I used an input voltage source of
>47.4 Volts - representing a 1 m / sec input to the phone I was modeling
>(a Mark Products L-25A-1.
>
>Brett - have you had a chance to study the noise in your model?  I will
>try to duplicate your PS-4.5B model in CCICAP and see what the noise is
>predicted to be.  I am using LT1007A op-amp models.
>
>--
>==================================================================
>Bob Smither                                        Bob@...........
>
>   "We make money the old fashioned way.  We print it."
>    --Art Rolnick, Chief Economist, Minnepolis Federal Reserve Bank
>==================================================================
>
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