Thanks again Pete...............If I have a coil which measures 1.2K =
ohms,  and another at 2.4K ohms.............what approx. value should I =
try?     Should I use a Pot and adjust until I get the effect I need and =
then measure the resistor value?

Ted
  ----- Original Message -----=20
  From: Pete Rowe=20
  To: psnlist@.................
  Sent: Thursday, December 16, 2010 1:18 PM
  Subject: Re: Geophone Damping Mass Slew rate




        --- On Thu, 12/16/10, Ted Channel  wrote:


          From: Ted Channel 
          Subject: Re: Geophone Damping Mass Slew rate
          To: psnlist@..............
          Date: Thursday, December 16, 2010, 12:11 PM


          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? I have for 20 years and

          Do you give up anything (voltage) by using a resistor on the =
coil?My coil measures about 10 k ohms and I use about 1 k for critical =
damping. I don't lose any sensitivity

          If it works, why do we still use magnet plates to damp? It =
works so well, I don't know why it isn't more popular.
          Pete Rowe


          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,

                 Chris Chapman=20






Thanks again Pete...............If I =
have a coil=20
which measures 1.2K ohms,  and another at 2.4K =
ohms.............what=20
approx. value should I try?     Should I use a Pot =
and=20
adjust until I get the effect I need and then measure the resistor=20
value?
 
Ted

  
----- Original Message ----- 
  From:=20
  Pete =
Rowe 
  
To: psnlist@.............. =

  
Sent: Thursday, December 16, =
2010 1:18=20
  PM
  
Subject: Re: Geophone Damping =
Mass Slew=20
  rate
  


  

    

    

      


--- On Thu, 12/16/10, Ted Channel =
<tchannel@............>=20
        wrote:

        
From:=20
          Ted Channel <tchannel@............>
Su=
bject:=20
          Re: Geophone Damping Mass Slew rate
To: psnlist@..............
Date=
:=20
          Thursday, December 16, 2010, 12:11 PM


          

          

          
This is kind of the same=20
          subject..................I understand you can dampen a coil =
with a=20
          resistor,  
          
 
          
Does anyone use this method =
in place of a=20
          Lehman style magnet plate? I have=20
          for 20 years and

          
Do you give up anything =
(voltage) by=20
          using a resistor on the coil?My=20
          coil measures about 10 k ohms and I use about 1 k for critical =

          damping. I don't lose any sensitivity

          
If it works, why do we still =
use magnet=20
          plates to damp? It works =
so well,=20
          I don't know why it isn't more popular.
Pete=20
          Rowe

          
 
          
Thanks, Ted
          
            
----- Original Message ----- =

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


            
            
            
            
            
            
            
            
            

            
            I=20
            have been playing around with a dismantled SPZ=20
            geophone damping and find if you short the leads to the coil =
and then drop the mass 
the mass =
will descend=20
            slowly, I guess from meeting the generator current =
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=20
            mass would fall 
  a bit then stay forever =
hovering=20
            ? 
 
   =20
            Correct
             
            2.the=20
            geophone is acting just like a rotating electrical generator 
armature developing torque under electrical loads=20
            ? 
 
   =20
            Correct
             
            3.=20
            It seems to me that seismic noise rarely hits the resonant frequency and 
  you might do better to not increase the =
damping over=20
            what already 
  is there =
in the=20
            mechanical and physical sense ?
             
                No. The critical damping allows =
you to=20
            get an output voltage flat with frequency above the =
resonant=20
            frequency. 
 
4. Does the rate at =
which the=20
            geophone mass drop under heavy=20
            damping represent some new =
fundamental=20
            Eigen frequency?
            
    No. The resonance is =
determined by=20
            the mass of the armature and the spring constant.=20
 
             
            5.=20
            Can anyone provide me with high school =

            math models which represent the mechanical and electrical=20
            behaviors of the geophone? 
  High=20
            school math being trig and algebra minus the calculus?
             
                The theory is freely available =
on the=20
            Internet.
             
            an Eigen freq not contained in EQ=20
            signals then do no damping=20
            at all? 
This=20
            [little damping] should work for weak EQ signals=20
            and not close strong ones =
? 
             
                  An undamped =
geophone has=20
            a single frequency peaked response - definitely NOT what you =

            want!  
            
     Regards,
             
                 Chris=20
            =
Chapman