I havent shielded the caps in my LTC1043-/2-Testdivider yet, but varying the Vcc couldnt compensate the about -40µV offset which i had.
Hello,
Shielding of the capacitors has only minor effects. (In my newer designs I only have a copper area under the floating capacitor.)
40uV offset is neither the LTC1043 nor the buffer op-amp.
I guess you are having either a common conductor (star grounding) problem or a EMI-problem.
In my early designs I had problems by the used ADC (LTC2400).
The switching noise from the input of the ADC has been rectified on the output stage (ESD protection diodes?) of the buffer amplifier.
This gave around 20-30 uV negative "offset".
With a adapted R/C low pass between Buffer and ADC you should have less than 10 uV "offset". (typically -4 .. +4 uV)
(be carefully with the R/C to keep gain and linearity errors low see Data Sheet).
Of course the whole is also dependant on good decoupling of the LTC2400.
And the LTC1043 also needs at least 1 nF at the input.
with best regards
Andreas