Hi,
Wow - what a thread - 265 pages of dense pdf not to mention the linked docs. Took me a week of spare time reading and I feel I need to go back and read it all again to see if I missed anything
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Very educational, and many thanks.
To add a bit more data and ask a couple of questions...
I just acquired 3 x 03458-66509 ref boards with the aim of building a sort of Fluke 7001 clone. Attached is a little basic measured data FWIW - no noise or stability #s yet. I see that the accepted wisdom is that HP set these to run at ~90C rather than a preferred ~60C.
I also see from the 3458a schematic (e.g.
http://www.maxmcarter.com/vref/hp3458-1.gif ) that the bases of the embedded temperature sensing transistor and the temperature control transistor are connected off the board as J400(1) and J401(1). I can't quite see from the CLIP where these go to and what they're used for. Anyone else figure this out yet?
Also I need to make some covers for the refs to keep out the drafts
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I can't see any detailed images of the HP design, so I've spun my own (also attached).
Any feedback? - I really don't know much about thermal. I've taken some inspiration from the L399 cover which has a double wall.
Regards, Alan