In a message dated 06/02/2010, gmvoeth@........... writes:

What i  mean is a coil like a center tapped inductor

+.......|
C
O
Gnd.....|
I
L
-.......|

CO part  and the IL part have to be identical. I do not know if you can 
wind such a  thing all at once or need two identical yet seperate coil magnet  
assemblies.
Hi Geoff,
 
    You can wind it quite easily using two supply reels  winding on both 
wires at the same time.

Forget  the amplifier part altogether, use what you want.
    The ordinary single opamp with four resistors will  allow you to wind a 
single coil and use an amplifier of that type.

I have  never built such a singular thing and can only guess where to begin.

I  do know that inital signal strength and signal to noise ratio is 
paramount for  any sensor at all and not just for areas of our own interest.

Easiest  way to get a good signal to noise ratio seems to be to use a two 
ton (avd.)  mass instead of a two pound (avd.) one. The highest density 
material you can  afford.
    That is not neccessary or desirable.

Superconducting wire sounds ideal yet none at room temp as far as I  know.
    There is none and unlikely to be any in the  future.

At the  moment i am thinking two of your coil/magnet ideas in additive 
fashion  connected to the same mass.
Two coils should double the signal right from  the start. Four would 
quadruple it.


You usually do better by doubling the number of  turns on a coil. A large 
increase in the output can be readily achieved by using  thicker NdFeB 
magnets, rather than by using more turns on the coil. The limit is  set by 
diamagnetic forces on the copper wire at the edges of the magnets. Copper  wire 
varies in it's magnetic properties.
    If you use a true differential amplifier like the  INA118 with a double 
wound coil, you can use finer wire since the coil  resistance is not so 
important. Calculate the kT noise voltage in the coil. 
 
    Regards,
 
    Chris  Chapman   





In a message dated 06/02/2010, gmvoeth@........... writes:
What i=20
  mean is a coil like a center tapped inductor

+.......|
 =
  =20
      C
        O
Gnd.....|
 =
  =20
      I
        L
-.......|

CO=
 part=20
  and the IL part have to be identical. I do not know if you can wind such=
 a=20
  thing all at once or need two identical yet seperate coil magnet=20
  assemblies.
Hi Geoff,
 
    You can wind it quite easily using two supply=
 reels=20
winding on both wires at the same time.
Forget=20
  the amplifier part altogether, use what you want.
    The ordinary single opamp with four resistors=
 will=20
allow you to wind a single coil and use an amplifier of that type.
I have=20
  never built such a singular thing and can only guess where to begin.
=

I=20
  do know that inital signal strength and signal to noise ratio is paramou=
nt for=20
  any sensor at all and not just for areas of our own interest.

Eas=
iest=20
  way to get a good signal to noise ratio seems to be to use a two ton (av=
d.)=20
  mass instead of a two pound (avd.) one. The highest density material you=
 can=20
  afford.
    That is not neccessary or desirable.
Superconducting wire sounds ideal yet none=
 at room temp as far as I=20
  know.
    There is none and unlikely to be any in the=
=20
future.
At the=20
  moment i am thinking two of your coil/magnet ideas in additive fashion=
=20
  connected to the same mass.
Two coils should double the signal right=
 from=20
  the start. Four would quadruple it.


    You usually do better by doubling the number=
 of=20
turns on a coil. A large increase in the output can be readily achieved by=
 using=20
thicker NdFeB magnets, rather than by using more turns on the coil. The li=
mit is=20
set by diamagnetic forces on the copper wire at the edges of the magnets.=
 Copper=20
wire varies in it's magnetic properties.
    If you use a true differential amplifier like=
 the=20
INA118 with a double wound coil, you can use finer wire since the coil=20
resistance is not so important. Calculate the kT noise voltage in the coil=
..=20

 
    Regards,
 
    Chris=20
Chapman