Hi Folks,  Thanks Chris for the links below, the UK School project was =
very nice.  =20

Here is an unrelated question, except the UK site explained the use of =
the software, Amaseis..........which I have use and I am still using it =
at some stations.   It has a feature which allow you to "replay" the =
recorded helicorder, trace and speed it up.   The result is impressive =
as you can replay and watch the event unfold in just a few seconds.   My =
question is there a way to capture this 10 or 15 second screen event and =
save it as some kind of movie file which could be emailed to others.    =
I do not see this "replay" feature in WinSDR.  So this feature may only =
be on Amaseis.

Thanks, Ted
  ----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Saturday, January 24, 2009 3:49 PM
  Subject: Re: home made vertical seismometer


  In a message dated 24/01/2009, rog@.......... writes:
    I have just joined the list and am looking for suggestions for good=20
    examples and instructions for home made vertical seismometers.

  Hi Robert,

      It is only possible to make a simple vertical seismometer with a =
stable period of less than about 6 seconds. This is due to the large =
temperature coefficient of Young's Modulus for steel. If you try to make =
one with a much longer period, it simply collapses as the room =
temperature rises a few degrees. Elinvar and Ni-SpanC springs were =
developed to overcome the problem, but you also need a quite critical =
design, first described in 1934 by LaCoste. See the references on =
http://psn.quake.net/infoequip.html

      Another approach is to make a simple seismometer with a period of =
maybe 1.5 to 2 seconds and then selectively compensate the F^2 signal =
response drop off below resonance with a 1/F^2 amplifier. You can extend =
the period by up to about x20 this way, but you need to design very low =
noise electronics. See http://jclahr.com/science/psn/hill/index.html  =
but DO use magnetic damping, NOT oil!

      The other approach to get longer stable periods is to use a =
similar setup, but to provide a 3 element force feedback system. Look at =
the STM-8 on psn, designed by Sean Morrissey =
http://www.eas.slu.edu/People/STMorrissey/index.html and =
http://www.bryantlabs.net/seismo.html

      I don't want to discourage you, but it is MUCH easier to make a =
good horizontal seismometer with a period of up to 30 seconds. See =
http://www.bgs.ac.uk/schoolseismology/ and click on 'seismometer'. See =
also the Volksmeter at http://www.rllinstruments.com/

      Regards,

      Chris Chapman







Hi Folks,  Thanks Chris for the links below, the UK School =
project was=20
very nice.   
 
Here is an unrelated question, except the UK site explained the use =
of the=20
software, Amaseis..........which I have use and I am still using it at =
some=20
stations.   It has a feature which allow you to "replay" the =
recorded=20
helicorder, trace and speed it up.   The result is impressive =
as you=20
can replay and watch the event unfold in just a few seconds.   =
My=20
question is there a way to capture this 10 or 15 second screen event and =
save it=20
as some kind of movie file which could be emailed to =
others.    I=20
do not see this "replay" feature in WinSDR.  So this feature may =
only be on=20
Amaseis.
 
Thanks, Ted

  
----- Original Message ----- 
  From:=20
  ChrisAtUpw@....... 
  
To: psn-l@.............. 
  
Sent: Saturday, January 24, =
2009 3:49=20
  PM
  
Subject: Re: home made vertical =

  seismometer
  


  

  
In a message dated 24/01/2009, rog@.......... writes:
  I have=20
    just joined the list and am looking for suggestions for good =

examples=20
    and instructions for home made vertical=20
  seismometers.

  

  
Hi Robert,
  
 
  
    It is only possible to make a simple =
vertical=20
  seismometer with a stable period of less than about 6 seconds. This is =
due to=20
  the large temperature coefficient of Young's Modulus for steel. If you =
try to=20
  make one with a much longer period, it simply collapses as the room=20
  temperature rises a few degrees. Elinvar and Ni-SpanC springs were =
developed=20
  to overcome the problem, but you also need a quite critical design, =
first=20
  described in 1934 by LaCoste. See the references on http://psn.quake.net/infoequ=
ip.html
  
 
  
    Another approach is to make a simple =
seismometer=20
  with a period of maybe 1.5 to 2 seconds and then selectively =
compensate the=20
  F^2 signal response drop off below resonance with a =
1/F^2 amplifier. You=20
  can extend the period by up to about x20 this way, but you need to =
design very=20
  low noise electronics. See http://jclahr.com/=
science/psn/hill/index.html  but=20
  DO use magnetic damping, NOT oil!
  
 
  
    The other approach to get longer stable =
periods=20
  is to use a similar setup, but to provide a 3 element force =
feedback=20
  system. Look at the STM-8 on psn, designed by Sean Morrissey http://www.=
eas.slu.edu/People/STMorrissey/index.html and=20
  http://www.bryantlabs.net/=
seismo.html
  
 
  
    I don't want to discourage you, but it is =
MUCH=20
  easier to make a good horizontal seismometer with a period of up to 30 =

  seconds. See http://www.bgs.ac.uk/scho=
olseismology/ and=20
  click on 'seismometer'. See also the Volksmeter at http://www.rllinstruments.com/
  
 
  
    Regards,
  
 
  
    Chris Chapman