In a message dated 2008/02/16, Brett3mr@............. writes:

> Yes, I agree the forcing coil/magnet also introduce effects similar to what 
> 
> I was describing for the integrator capacitor; except that you can avoid 
> the coil resistance issues by using a current driver.  It's obvious that 
> you can't depend on electronic feedback to do all your centering, forever, 
> but must occasionally turn a screw to unload the feedback loop.

Hi Brett,

       My train of thought was to either compensate or to drastically reduce 
the main error drifts. I use a small thermostat circuit to keep crystal 
temperatures constant to better than 0.1 C Deg. I could wrap one nicely around a 
capacitor. If you used an electromagnet, you could keep the field constant to a 
few ppm. An alternative would be to control the temperature of the magnets. 
       The biggest drift is likely that of a steel spring. Can you get 
Ni-SpanC wire? sheet? I can get Invar wire, but not Elinvar at the moment.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/02/16, Brett3mr@............. writes:



Yes, I agree the forcing coil/m=
agnet also introduce effects similar to what 

I was describing for the integrator capacitor; except that you can avoid 
the coil resistance issues by using a current driver.  It's obvious tha=
t 

you can't depend on electronic feedback to do all your centering, forever, <=
BR>
but must occasionally turn a screw to unload the feedback loop.
=




Hi Brett,



       My train of thought was to either compe=
nsate or to drastically reduce the main error drifts. I use a small thermost=
at circuit to keep crystal temperatures constant to better than 0.1 C Deg. I=
 could wrap one nicely around a capacitor. If you used an electromagnet, you=
 could keep the field constant to a few ppm. An alternative would be to cont=
rol the temperature of the magnets. 

       The biggest drift is likely that of a s=
teel spring. Can you get Ni-SpanC wire? sheet? I can get Invar wire, but not=
 Elinvar at the moment.



       Regards,



       Chris Chapman