This is kind of the same subject..................I understand you can =
dampen a coil with a resistor, =20

Does anyone use this method in place of a Lehman style magnet plate?
Do you give up anything (voltage) by using a resistor on the coil?
If it works, why do we still use magnet plates to damp?

Thanks, Ted
  ----- Original Message -----=20
  From: Christopher Chapman=20
  To: psnlist@.................
  Sent: Thursday, December 16, 2010 10:00 AM
  Subject: Re: Geophone Damping Mass Slew rate


  I have been playing around with a dismantled SPZ geophone damping and =
find if you short the leads to the coil and then drop the mass=20
  the mass will descend slowly, I guess from meeting the generator =
current being dissipated by the internal resistance.=20
  =20
  Questions arise from this.=20
  =20
  1. if there were no internal resistance (superconductor)   then when =
the leads are shorted the mass would fall=20
    a bit then stay forever hovering ?=20
  =20
      Correct

  2.the geophone is acting just like a rotating electrical generator=20
  armature developing torque under electrical loads ?=20
  =20
      Correct

  3. It seems to me that seismic noise rarely hits the resonant =
frequency and=20
    you might do better to not increase the damping over what already=20
    is there in the mechanical and physical sense ?

      No. The critical damping allows you to get an output voltage flat =
with frequency above the resonant frequency.=20
  =20
  4. Does the rate at which the geophone mass drop under heavy damping =
represent some new fundamental Eigen frequency?

      No. The resonance is determined by the mass of the armature and =
the spring constant. =20

  5. Can anyone provide me with high school math models which represent =
the mechanical and electrical behaviors of the geophone?=20
    High school math being trig and algebra minus the calculus?

      The theory is freely available on the Internet.

  an Eigen freq not contained in EQ signals then do no damping at all?=20
  This [little damping] should work for weak EQ signals and not close =
strong ones ?=20

        An undamped geophone has a single frequency peaked response - =
definitely NOT what you want! =20

       Regards,








This is kind of the same =
subject..................I=20
understand you can dampen a coil with a resistor,  
 
Does anyone use this method in place of =
a Lehman=20
style magnet plate?
Do you give up anything (voltage) by =
using a=20
resistor on the coil?
If it works, why do we still use magnet =
plates to=20
damp?
 
Thanks, Ted

  
----- Original Message ----- 
  From:=20
  Christopher=20
  Chapman 
  
To: psnlist@.............. =

  
Sent: Thursday, December 16, =
2010 10:00=20
  AM
  
Subject: Re: Geophone Damping =
Mass Slew=20
  rate
  


  

  

  

  

  

  

  

  

  

  

  I=20
  have been playing around with a dismantled SPZ =
geophone damping and find if you short=20
  the leads to the coil and then drop the =
mass 
the=20
  mass will descend slowly, I guess from meeting the generator =
current=20
  being dissipated by the internal=20
  resistance. 
 
Questions arise from=20
  this. 
 
1. if there were no internal resistance=20
  (superconductor)   then when the leads are shorted the mass =
would=20
  fall 
  a bit then stay forever hovering=20
  ? 
 
    =
Correct
   
  2.the=20
  geophone is acting just like a rotating electrical generator 
armature developing=20
  torque under electrical loads ? 
 
    Correct
   
  3.=20
  It seems to me that seismic noise rarely hits the resonant=20
  frequency and 
  you might do =
better to not=20
  increase the damping over what already 
  is=20
  there in the mechanical and physical sense ?
   
      No. The critical damping allows you to =
get an=20
  output voltage flat with frequency above the resonant=20
  frequency. 
 
4. Does the rate at which the =
geophone=20
  mass drop under heavy damping represent some new fundamental Eigen frequency?
  
    No. The resonance is determined by =
the mass of=20
  the armature and the spring constant.  
   
  5.=20
  Can anyone provide me with high school =
math models which represent the =
mechanical=20
  and electrical behaviors of the geophone? 
  High school math being trig =
and=20
  algebra minus the calculus?
   
      The theory is freely available on the=20
  Internet.
   
  an Eigen freq not contained in EQ signals=20
  then do no damping at =
all? 
This [little =
damping] should=20
  work for weak EQ signals and not close=20
  strong ones ? 
   
  
      An undamped geophone has =
a single=20
  frequency peaked response - definitely NOT what you want!  =

  
     Regards,

   
  
     Chris=20
  =
Chapman