the disappointment will come.

as so many before, you confuse resolution and precision.

Erik Malund said:

take as an example an 8 bit ADC where 1V raeds 047h and 1,01v reads 048h. what do you expect if the input is 1.005V/ a tolerance/stability of a picovolt???
Jason replied
Hmmm.... 1.005V > 0.005 Picovolts?? mVolts surely?

nope, picoVolt. assume a perfect A/D (there is none such) it will read 047h at 1,005000000000000000 and read 048h at 1,005000000000000001.

I'm not using TC520A but instead drive the TC500A directly from the MCU, pushing 20 bits resolution out of it
That's DEAD EASY, getting better than, say 10 bits of precision is really tough.

Lets face it, both Fluke and Agilent are at the forefront of measurement technology? The thing is one can download service manuals complete from Agilent/fluke totally free. Reading and studying these manuals gives insight into how these instruments work which is what I have been doing for some time.
sure, but realize that e.g. a Fluke voltmeter is no better than about 10 bits in precision )corresponding to 1mV in a 2V range).

Erik