In a message dated 2006/11/11, gpayton880@....... writes:

> Where may I find details for constructing magnetic damping for a Lehman 
> sensor, please.
> Thank you,
> Jerry Payton

Hi Jerry,

       Have a look at http://jclahr.com/science/psn/chapman/lehman/index.html
       and for magnets at   
       http://jclahr.com/science/psn/chapman/as1%20damping/index.html
       I use 20mm x 10 mm x 5mm NdFeB bar magnets with a 1 Kg mass. You may 
need the 1" x 1/2" x 1/4" magnets with a larger mass.
       Another source is www.amazingmagnets.com

       Try using a horizontal tongue of 1/16" copper. This is a bit of 
overkill, but you can then increase the central magnet gap to make adjustment 
easier. I suggest using a tongue about 2" wide - this allows a movement of about 
+/-10mm with the construction shown. You want the tongue to totally cover the 
magnet block at maximum travel, to avoid any edge effects. Cu hasn't given me any 
problems but AlSi is paramagnetic with 5x the susceptibility. There are quite 
high fields at the edges of the magnet block.   

       I suggest that you place the damping blade vertically level with the 
centre of mass of the arm. This ensures that there is no tendency for the arm 
to rotate about it's long axis if you are using a single wire suspension.

       Regards,

       Chris Chapman
In a me=
ssage dated 2006/11/11, gpayton880@....... writes:



Where may I find details for co=
nstructing magnetic damping for a Lehman sensor, please.

Thank you,

Jerry Payton




Hi Jerry,



       Have a look at http://jclahr.com/scienc=
e/psn/chapman/lehman/index.html

       and for magnets at   

       http://jclahr.com/science/psn/chapman/a=
s1%20damping/index.html

       I use 20mm x 10 mm x 5mm NdFeB bar magn=
ets with a 1 Kg mass. You may need the 1" x 1/2" x 1/4" magnets with a large=
r mass.

       Another source is www.amazingmagnets.co=
m



       Try using a horizontal tongue of 1/16"=20=
copper. This is a bit of overkill, but you can then increase the central mag=
net gap to make adjustment easier. I suggest using a tongue about 2" wide -=20=
this allows a movement of about +/-10mm with the construction shown. You wan=
t the tongue to totally cover the magnet block at maximum travel, to avoid a=
ny edge effects. Cu hasn't given me any problems but AlSi is paramagnetic wi=
th 5x the susceptibility. There are quite high fields at the edges of the ma=
gnet block.   



       I suggest that you place the damping bl=
ade vertically level with the centre of mass of the arm. This ensures that t=
here is no tendency for the arm to rotate about it's long axis if you are us=
ing a single wire suspension.



       Regards,



       Chris Chapman