HP 3458A (and other) DMM ADC and analog front end details

[rhb]

I'm about to write a program to model a voltage reference with 1/f and thermal noise.   I need to account for the anti-alias filter.   At 8.5 digits, the requirements are rather daunting and will need to be handled properly.

Can someone point me to where I can find a detailed description of the input design of any of the high end DMMs?  I've downloaded all the application notes and manuals from the 3458A page, but I noticed is was "assembly level" service.

I'll try the 3456A documentation later.

[Dr. Frank]

For the 3458A, the schematics are available,  'CLIP', but no Theory Of Operation.
A good analysis of the front ends of 34401A and 34420A are in the latest issue of The  Art Of Electronics.
Frank

[alm]

In addition to the service manuals, you may also find some "theory of operation" level information in HP Journal issues about the meter:
3458A: April, 1989 issue (PDF link)
3457A: February, 1986 issue (PDF link)
3456A: April, 1981 issue (PDF link)
3455A: February, 1977 issue (PDF link)

Not sure if any of them cover the front-end to the level of detail you desire.

[rhb]

The HPJ discussion about the 3458A ADC is great, but I so wish it were not in blue ink.  Many thanks.  I'll probably download the entire archive.