From calibration protocol (of yesterday):
for +10V the 3458A reading was 3.4 uV too high against calibrator actual value.
for -10V the 3458A reading was 4.1 uV (amount too high)
Calibration uncertainity is 2.5 ppm (+/-25uV) with 24 hrs we get 2.6 ppm (+/-26uV)
so for 10V + 56.8uV we have to correct to 10V + 53.4 uV
for -10V -58.5uV we have to correct to -10V - 54.4uV
the difference to 10V + 41uV from Fluke 7000 is 12.4 or 13.4 uV which is within the +/- 26 uV +/- 2.5 uV uncertainity.
But which device is showing the truth? -> we need more references/DMMs
Edit: what where the results between the Fluke 7000 and the other Flukes (732)?
Edit: And even more evil: I did not find in the calibration protocol if the calibrator has been already set for the new volt
with best regards
Andreas
Andreas,
I have compared the 732A from Adrian, 732A from Wulf (?), 7000 from Michel, and my LTZ #2
Procedure was similar to yours:
using a freshly adjusted 3458A (to Adrians 732A), I measured each polarity @ DUT, 16 x NPLC100, with statistics.
Average of these two absolute value gives "true reading", to cancel e.m.f.
Adrians 732A (10.000 010 V
nom.) was uncertain to 0.5ppm, Michels 7000 (10.000 041 V
nom.) was uncertain to 0.25ppm, so it got double weight for the difference calculus.
I calculated corrected values for these references:
732A (Adrian) = 10.000 006 5 V (StD ~ 200nV)
7000 (Michel) = 10.000 042 7 V (StD ~ 130nV)
732A (Wulf?) = 10.000 008 5 V (StD ~ 132nV)
LTZ#2(Frank) = 7.118 228 61 V (StD ~ 104nV)
The agreement between these 732A and the 7000 'felt' really impressive.
I had to correct my baseline (drift of my 3458A) by about +1.8 ppm. I.e. my 3458A was reading too low.. maybe that's the -2ppm Philipp was looking for.
But this is also quite impressive, as the last direct transfer was done 7 years ago, and that demonstrates that an ensemble of 4 references (LTZ and SZA) determines drifts in the sub-ppm range, and also is capable of < 1ppm/yr. drift performance (ovens at 50..55°C).
Not bad for home-grown references.
A big Thank You to André (branadic), who made that event happen.. it was perfectly organized.
It also was a great experience and a great pleasure with all participants.. I really felt deeply inside, that I'm not alone being 'nuts'.
Frank