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

• HP 3458A (and other) DMM ADC and analog front end details
  Posted by rhb on 14 Apr, 2018 17:04
• 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.
• #1 Reply
  Posted by Dr. Frank on 14 Apr, 2018 17:26
• 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
• #2 Reply
  Posted by alm on 14 Apr, 2018 18:00
• 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.
• #3 Reply
  Posted by rhb on 14 Apr, 2018 20:23
• 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.