Hi Chris,
Thanks for sending information on imnproving the C-Spring Sensor.  Just =
a quick correction on the link to Robert's circuit for extending the =
period of geophones.  Leave out the "epics" part of your link.
http://www.jclahr.com/science/psn/roberts/index.html

How would you compare the C-Spring sensor to an AS-1 type vertical =
seismometer modified with either a "piano wire hinge" or a razer blade =
hinge clamped at both ends?

Kay



----- Original Message -----=20
  From: Christopher Chapman=20
  To: psnlist@.................
  Sent: Wednesday, January 19, 2011 7:31 AM
  Subject: Re: C-Spring Sensor - 5/6 Second Period




  Subject: C-Spring Sensor - 5/6 Second Period


  Has anyone tried this one? A vertical with a 5 to 6 second period =
using two hacksaw blades. Would like to hear opinions as to whether this =
is a worth-while build.

  http://www.fairpoint.net/~sparksite/CSpring%20Printer.html

  Hi Richard,

      This is an old design. Never use oil damping. It is non linear =
both with period and with amplitude. It is hideously temperature =
sensitive and it is not easy to adjust..

      There is a design for a magnetic damper for a vertical seismometer =
at www.jclahr.com/science/psn/chapman/as1%20damping/index.html Mount the =
1/16" thick copper damping blade on the arm and put the quad damping =
magnet block on the base. You can use soft Aluminum sheet for the blade =
- if you can buy it - NOT hard or alloy sheet - but copper is better, =
since it is not significantly diamagnetic.

      Buy fully hardened hacksaw blades.The ordinary ones have a =
hardened edge, but with a softer blade. Grind off both the teeth and the =
wavy bends on the base, otherwise you get cracks developing quite =
rapidly when the blade is stressed.

       DON'T mount a magnet on a seismometer arm. It picks up noise from =
the Earth's magnetic  field, current surges in the house wiring, the =
movement of large vehicles, etc. Mount the pickup coil on the arm and =
use a shielded quad NdFeB magnet block, or use an optical position =
detector.

      The response can easily be extended to over 20 seconds using =
Robert's circuit for extending the period of geophones. You can get a =
x10 period extension before running into sensor / amplifier noise, but =
it does mean that you have to build your own specialised amplifier - not =
too difficult to do using stripboard? See =
www.jclahr.com/science/psn/epics/roberts/index.html=20

      Do look through the articles on the jclahr website.

      Regards,








Hi Chris,
Thanks for sending information on imnproving the =
C-Spring=20
Sensor.  Just a quick correction on the link to Robert's circuit =
for=20
extending the period of geophones.  Leave out the "epics" part of =
your=20
link.
http://www.=
jclahr.com/science/psn/roberts/index.html
 
How would you compare the C-Spring sensor to an =
AS-1 type=20
vertical seismometer modified with either a "piano wire hinge" or a =
razer blade=20
hinge clamped at both ends?
 
Kay
 
 
 
----- Original Message ----- 

  From:=20
  Christopher=20
  Chapman 
  
To: psnlist@.............. =

  
Sent: Wednesday, January 19, =
2011 7:31=20
  AM
  
Subject: Re: C-Spring Sensor - =
5/6 Second=20
  Period
  


  

  


  

  Subject:=20
  C-Spring Sensor - 5/6 Second Period


  

  
Has anyone tried this one? A vertical with a 5 to 6 second period =
using=20
  two hacksaw blades. Would like to hear opinions as to whether this is =
a=20
  worth-while build.
  
 
  
http://www.fairpoint.net/~sparksite/CSpring%20Printer.htm=
l
  
 
  
Hi Richard,
  
 
  
    This is an old design. Never use oil damping. =
It is=20
  non linear both with period and with amplitude. It is hideously =
temperature=20
  sensitive and it is not easy to adjust..
  
 
  
    There is a design for a magnetic damper for a =
vertical=20
  seismometer at www.jclahr.com/science/psn/chapman/as1%20damping/index.html=20
  Mount the 1/16" thick copper damping blade on the arm and put the quad =
damping=20
  magnet block on the base. You can use soft Aluminum sheet for the =
blade - if=20
  you can buy it - NOT hard or alloy sheet - but copper is better, since =
it is=20
  not significantly diamagnetic.
  
 
  
    Buy fully hardened hacksaw blades.The ordinary =
ones=20
  have a hardened edge, but with a softer blade. Grind off both the =
teeth=20
  and the wavy bends on the base, otherwise you get cracks =
developing=20
  quite rapidly when the blade is stressed.
  
 
  
     DON'T mount a magnet on a =
seismometer arm.=20
  It picks up noise from the Earth's magnetic  field, current =
surges in the=20
  house wiring, the movement of large vehicles, etc. Mount the pickup =
coil on=20
  the arm and use a shielded quad NdFeB magnet block, or use an optical =
position=20
  detector.
  
 
  
    The response can easily be extended to over 20 =
seconds=20
  using Robert's circuit for extending the period of geophones. You can =
get a=20
  x10 period extension before running into sensor / amplifier noise, but =
it does=20
  mean that you have to build your own specialised amplifier - not too =
difficult=20
  to do using stripboard? See www.j=
clahr.com/science/psn/epics/roberts/index.html=20
  
  
 
  
    Do look through the articles on the jclahr=20
  website.
  
 
  
    Regards,
  
 
  
    Chris Chapman