The high frequency pulses are actually quite easy to filter out with a
suitable low pass filtering. You may need to use appropriate shielding of
the high frequency circuit from the low frequency portions.

Matt

On Sun, May 16, 2010 at 9:07 AM, Chuck / Judy Burch wrote:

>
> Here's a technical question about seismometer electronics.  What phase
> sensitive detector design do you recommend for low noise?
>
> I have built PSDs using an op amp and FET switches (the amp switches
> between gain of +1 and -1).  Analog Technology and National Semi describe
> these circuits in application notes.  And you can use a switch with an
> instrumentation amp.  But these switches produce huge high frequency noise
> pulses that are very difficult to shield out or filter out.
>
> You could also use IC multipliers like the AD630 or a Gilbert cell
> multiplier.  I have not tried either of these and wonder if they are worth
> the cost and/or trouble of construction.
>
> Any suggestions?
>
> Thanks,
>
> Chuck Burch
>
>
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>
The high frequency pulses are actually quite easy to filter out with a suit=
able low pass filtering. You may need to use appropriate shielding of the h=
igh frequency circuit from the low frequency portions.


Matt

On Sun, May 16, 2010 at 9:07 AM, Chu=
ck / Judy Burch <cjburch@...........> wrote:



Here's a technical question about seismometer electronics. =A0What phas=
e sensitive detector design do you recommend for low noise?



I have built PSDs using an op amp and FET switches (the amp switches betwee=
n gain of +1 and -1). =A0Analog Technology and National Semi describe these=
 circuits in application notes. =A0And you can use a switch with an instrum=
entation amp. =A0But these switches produce huge high frequency noise pulse=
s that are very difficult to shield out or filter out.




You could also use IC multipliers like the AD630 or a Gilbert cell multipli=
er. =A0I have not tried either of these and wonder if they are worth the co=
st and/or trouble of construction.



Any suggestions?



Thanks,



Chuck Burch





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Public Seismic Network Mailing List (PSN-L)



To leave this list email PSN-L-REQUEST@.............. with the body of the messa=
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