PSN-L Email List Message

Subject: Re: NEVADA EVENT ??? M2.7 ??? seen in Apache Junction ??
From: Geoffrey gmvoeth@...........
Date: Mon, 9 May 2011 14:45:37 +0000

What will happen if you use the geophone between the negative
inputs in an Instrumentation amplifier comprised of three
typical op-amps ?


in some kind of Push Pull (Class "B") configuration with both geophone leads
attached somehow to two opposing operational amplifiers ?

Since the spice simulator will not simulate physics things other than electronics,
I can not experiment with geophones using the software, I now have.

It seems a person really needs a more complete simulator
to look at and test the real physical world.

-----Original Message----- 
From: Christopher Chapman
Sent: Monday, May 09, 2011 10:09 AM
To: psnlist@..............
Subject: Re: NEVADA EVENT ??? M2.7 ??? seen in Apache Junction ??

Subject: Re: NEVADA EVENT ??? M2.7 ??? seen in Apache Junction ??

It is odd but I am unable to get a flat velocity response cheaply.  I guess my waveform is displacement below 1 Hz and Acceleration 
Above 1Hz, Only right at 1Hz might you call it velocity.  What kind of seismometer is that ? Hi Geoff, If you put your 1 Hz geophone 
onto a high impedance non inverting amplifier input, you get a velocity response above the resonant frequency. You then increase the 
damping to ~critical by loading the geophone with a damping resistor. This is necessary to flatten out the high frequency response. 
Regards,Chris Chapman 


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