>That's why I asked for practical schematics, specially of the input
>amplifier stage (I'm very bad at analog electronics.....), I couldn't find

Oops, missed a couple.  Keithley Instruments has a thin little book
entitled "Low Level Measurements" that might help you out.  Stuff like
Kelvin connections, guarding, etc.  I think it's free upon request from a
Keithley dealer.

The National Semiconductor Linear Applications Handbook is another book
everyone should have.  It's pretty weak on load cell interfaces (maybe 3 or
4 circuits, but a lot gets rehashed by Williams in the LT book), but there
are several good V-F type circuits.  Some of it is starting to look a
little dated, though.  I think you can still request it (for free) from
their web site.


later,
newell