Mauro,
I'm not sure it will be _very_ sensitive to axial movements.  Horizontal
movements of the magnet will not cause as much change in magnetic 
flux linkage through the coil as vertical movements because of the geometry
of the coil and magnet.  For movement in one horizontal direction, the
magnet
is moving parallel to the wires at the top of the coil.  For the other
horizontal
direction, the magnet is moving parallel to the flux between it's poles.  In
either
case any flux change through the coil is a second order effect due to
curvature
of the coil and curvature of the magnet path.  For vertical movement the
flux 
change is a first order effect, proportional to displacement.  As a guess I 
would expect the horizontal sensitivity to be 5x to 10x down from the
vertical.  
 
Jack

-----Original Message-----
From: Mauro Mariotti [mailto:mariotti@..........
Sent: Monday, December 30, 2002 2:01 PM
To: psn-l@..............
Subject: Re: Notes to UK--Nick


Hi all,
I suggest a different approach for homemade vertical sensors.
The sensor in the link you propose is VERY sensitive to axial movements
(horizontal movements)

if you give a look to 
 
http://www.infoeq.it/doc02v_e.htm   
 
and scroll the page until you reach:
 
Lacoste suspension sensor 
 
you can see a good approach to a sensitive 
long period seismometer.
 
There are also sofisticated tecniques to 
have a virtually infinite response for that kind
of seismometer using a "zero length spring".
 
Mr Lacoste writed a lot of paper on it.
Chris Chapman is better documented on this point.
I hope to have the time to publish an abstract on these tecnmiques
but any clever mind can understand how the Lacoste suspension
is great and simple to build.
 
Regards
Mauro
 
 
 

----- Original Message ----- 
From: John   & Jan Lahr 
To: psn-l@..............   
Sent: Monday, December 30, 2002 6:47 PM
Subject: Re: Notes to UK--Nick

I've scanned Jim's Short Period design plans and put a copy on my web site
here:
http://jjlahr.com/science/psn/lehman/
 
This will save on postage and make the plans available to more people.  They
are a good example of how to document a seismic sensor design.

Happy New Year,
John



At 12:15 PM 12/28/2002, you wrote:


Nick--I do not need an e-mail address.  I only needed your mailing address
to send the "Short Period" design plans.
   The plans were mailed airmail  to U.K. 2 days before Christmas.
   A good New Year to you and all the PSN group.
                              J. Lehman.










Mauro,
I'm 
not sure it will be _very_ sensitive to axial movements.  
Horizontal
movements of the magnet will not cause as much change in magnetic 

flux 
linkage through the coil as vertical movements because of the 
geometry
of the 
coil and magnet.  For movement in one horizontal direction, the 
magnet
is moving parallel to the wires at the top of the 
coil.  For the other horizontal
direction, the magnet is moving parallel to the flux 
between it's poles.  In either
case any flux change through the coil is a second order 
effect due to curvature
of the coil and curvature of the magnet 
path.  For vertical 
movement the flux 

change is a first order effect, proportional to 
displacement.  As a 
guess I 

would expect the horizontal 
sensitivity to be 5x to 10x down from the 
vertical.  
 
Jack

  
-----Original Message-----
From: Mauro Mariotti 
  [mailto:mariotti@..........
Sent: Monday, December 30, 2002 2:01 
  PM
To: psn-l@..............
Subject: Re: Notes to 
  UK--Nick


  
Hi all,
  
I suggest a different approach for homemade 
  vertical sensors.
  
The sensor in the link you propose is VERY 
  sensitive to axial movements
  
(horizontal movements)
  

  
if you give a look to 
  
  
 
http://www.infoeq.it/doc02v_e.htm 

  
 
  
and scroll the page until you 
  reach:
  
 
  
Lacoste suspension sensor 
  
  
 
  
you can see a good approach to a sensitive 
  
  
long period seismometer.
  
 
  
There are also sofisticated tecniques to 
  
  
have a virtually infinite response for that 
  kind
  
of seismometer using a "zero length 
  spring".
  
 
  
Mr Lacoste writed a lot of paper on 
  it.
  
Chris Chapman is better documented on this 
  point.
  
I hope to have the time to publish an abstract 
  on these tecnmiques
  
but any clever mind can understand how the 
  Lacoste suspension
  
is great and simple to build.
  
 
  
Regards
  
Mauro
  
 
  
 
  
 
  

    
----- Original Message ----- 
    
From: 
    John & Jan 
    Lahr 
    
To: psn-l@.............. 
    
Sent: Monday, December 30, 2002 6:47 
    PM
    
Subject: Re: Notes to UK--Nick
    

I've scanned Jim's Short Period design plans and put a copy 
    on my web site here:
http://jjlahr.com/science/psn/lehman/
This will save 
    on postage and make the plans available to more people.  They
are a 
    good example of how to document a seismic sensor design.

Happy New 
    Year,
John



At 12:15 PM 12/28/2002, you wrote:

    
Nick--I do not 
      need an e-mail address.  I only needed your mailing address to send 
      the "Short Period" design plans.
   The 
      plans were mailed airmail  to U.K. 2 days before 
      Christmas.
   A good New Year to you and 
      all the PSN group.
                              
      J. Lehman.