This whole discussion does not really apply to the LTZ1000 circuit, that
is the bare 7.15..V output, w/o step up amplifier, as all drift
parameters were attenuated by orders of magnitude, depending on the
resistors, R1-R5.
In the eevblog thread, several volt-nuts measured the real dependency,
in contrast to the datsheet, which simply claims 1:100 attenuation for
each of these resistors:
R1 R2 R3 R4 R5 author
120 70000 70000 12-15k 1k
-1/770 -1/250 -1/1400 +1/100
janaf
-1/600 -1/238 -1/1000 +1/87
lars
-1/656
TiN
1/714 1/250 1/3333 1/105
bbs38hot
-1/670 -1/238 -1/1184 +1/74 -1/75 Andreas
Therefore, even humidity effects at most affect R4/R5, with 1/75 impact.
I also think, that it's possible for volt-nuts to measure such residual
effects, by assembling several references, keeping the parameter of
question (e.g. humidity or temperature) constant for the master
reference, varying this paramater for a DUT, and evaluating the drift by
monitoring the difference between the references.
Same goes for longterm drift, by using a group of many references (A man
with one, two, three clocks..)
In the end, maintaining ultra precise references at first requires to
care for controlled/constant ambient parameters, than to put too much
effort to design references, which are immune to all possible drift factors.
Frank
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