PSN-L Email List Message

Subject: Seismic Pre-Amp
From: "Randall Pratt" rpratt@.............
Date: Thu, 16 Dec 2010 15:21:43 -0600


 

Pete,

 

I have used your design for about 10 years primarily with fairly low coil
resistance.  I see matching resistors were specified as about 5.1 K on each
end of the 7 to 21 K coil but I have used coils of less than 1 K and
anywhere from no resistors to 10K on each end.   What I have noted most is a
slight reduction in output and maybe some less noise with some resistance
included.  I do not use a damping resistor because a large mass is simply
not possible to damp from the coil output with my magnets.

 

Not to be confused with damping resistance, I have also wondered how to
determine the value for the matching resistors between the coil and the op
amp inputs.  

 

Can you explain more?

 

Randy












 

Pete,

 

I have used your design for about 10 years primarily = with fairly low coil resistance.  I see matching resistors were = specified as about 5.1 K on each end of the 7 to 21 K coil but I have used coils of = less than 1 K and anywhere from no resistors to 10K on each end.   = What I have noted most is a slight reduction in output and maybe some less = noise with some resistance included.  I do not use a damping resistor because = a large mass is simply not possible to damp from the coil output with my = magnets.

 

Not to be confused with damping resistance, I have = also wondered how to determine the value for the matching resistors between = the coil and the op amp inputs. 

 

Can you explain more?

 

Randy


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