Chris,  By "an opinion" I guess I was thinking about the best hinge to =
use.  I have seen fishing line, thin metal hinges, wire hinges and knife =
points.
I know I would need lateral stability, so the arm would not bob side to =
side, but I also know it would need to have minimal friction.
On the AS1 it looks as if they just use a wide knife point approach.   =
Thanks, Ted
  ----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Monday, December 11, 2006 10:18 PM
  Subject: Re: Vertical Sensor


  In a message dated 2006/12/12, tchannel@.............. writes:


    Chris, I was very pleased with the coil/magnet arrangement you =
suggested, the one which sandwiched the four magnets between two plates. =
It was simple and effective. If I were to make another sensor, this time =
a vertical like the AS1, would you suggest the same approach, but =
modified for vertical rather than horz? Or to use the horseshoe magnet =
and coil? I am sure both would work, but I would like opinions on it.


  Hi Ted,

         Entirely up to you. I am not quite sure what you want as 'an =
opinion'?

         Quad 1" square NdFeB magnets on mild steel backing plates are =
likely to give you a much higher magnetic field than a U form Alnico =
magnet. They are almost certainly cheaper. Large new Alnico magnets are =
now quite expensive.=20
         If you wind a rectangular form coil, you can get a highly =
linear output and you won't need more than ~3,000 turns. Also, you get =
very little external stray field. Put the coil on the arm and the magnet =
assembly on the baseplate.=20
         Don't put any ferromagnetic material or a magnet on a =
seismometer arm - this makes the system very noisy.

         Just an opinion..... You have my drawings....








Chris,  By "an opinion" I guess I =
was thinking=20
about the best hinge to use.  I have seen fishing line, thin metal =
hinges,=20
wire hinges and knife points.
I know I would need lateral stability, =
so the arm=20
would not bob side to side, but I also know it would need to have =
minimal=20
friction.
On the AS1 it looks as if they just use =
a wide=20
knife point approach.   Thanks, Ted

  
----- Original Message ----- 
  From:=20
  ChrisAtUpw@....... 
  
To: psn-l@.............. 
  
Sent: Monday, December 11, 2006 =
10:18=20
  PM
  
Subject: Re: Vertical =
Sensor
  

In a=20
  message dated 2006/12/12, tchannel@..............=20
  writes:


  Chris, I was very pleased with the coil/magnet =
arrangement you=20
    suggested, the one which sandwiched the four magnets between two =
plates. It=20
    was simple and effective. If I were to make another sensor, this =
time a=20
    vertical like the AS1, would you suggest the same approach, but =
modified for=20
    vertical rather than horz? Or to use the horseshoe magnet and coil? =
I am=20
    sure both would work, but I would like opinions on it.

Hi=20
  Ted,

       Entirely up to you. I =
am not=20
  quite sure what you want as 'an=20
  opinion'?

       Quad 1" square =
NdFeB=20
  magnets on mild steel backing plates are likely to give you a much =
higher=20
  magnetic field than a U form Alnico magnet. They are almost certainly =
cheaper.=20
  Large new Alnico magnets are now quite expensive.=20
  
       If you wind a rectangular =
form coil,=20
  you can get a highly linear output and you won't need more than ~3,000 =
turns.=20
  Also, you get very little external stray field. Put the coil on the =
arm and=20
  the magnet assembly on the baseplate. =

      =20
  Don't put any ferromagnetic material or a magnet on a seismometer arm =
- this=20
  makes the system very =
noisy.

       Just=20
  an opinion..... You have my=20
  drawings....

       Chris =
Chapman=20