22-bit DC voltmeter (in)sane?

Optikon said:

You'll have a tough time. Don't use Ref02. Too drifty.. too much 1/f noise. At 22 bits (& higher) input noise (RF or otherwise) isnt going to be your major problem. It will be all the components you use in your design.

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I wont, I just read some more on the subject.. I also changed the ADC. It will be AD7793. It has a usable (up to 18-bit) internal referece, so if the overal design prooves itself, i'll seek to a 1ppm low noise external reference, to try to push out some more bits.

Optikon said:

Your input amplifier should be a low noise Jfet audio type.

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Probably. I have access to several low noise Op-amps, even chopper types, so I'll swap them out and see what will I get.