Hmm,
here in the volt nut section we don´t throw away any gear nor any digits
with best regards
Andreas
Hmmm indeed - There would be a lot of Professional Engineers / Metrologists / VoltNUts that would debate the issue of fantasy digits with you - but for for good engineering practice it is best to always keep track of your measurement uncertainty, measurement confidence, and keep your results reasonable to your test setup without adding "phantom accuracy" along the way.
Which by the way is something not up for debate - as a professional engineer, if I were to submit measurement results to an ISO 900x quality control audit team, the very first thing they check is the equipment used to make a measure and basic measurement accuracy, the last calibration date, the next calibration due date, the calibration history, any extrapolated calibration estimates based on past calibration cycles, and so on.
Then the very
next thing that would be examined is any subsequent calculations based on those measurements, and at any point was -any- apparent accuracy increased by the improper use of extra digits - for instance using 13 digits of precision to calculate a measurement made with a 6ppm accurate DMM. That would be cause for immediate loss of certification right there.
Everything gets boiled down to double-check that a certain testing procedure, if we are delivering a device that operates to some PPM accuracy - really does operate to that level, and is traceable back to NIST at every step. The whole idea is to cross-check at every step that accuracy is not lost or gained. High Resolution is not data if accuracy isn't there to match.
That is the only Head's Up there, and absolutely no offense intended to you or Branandic, and I apologize if it was taken that way. It wasn't meant to. Keep Building and Have Volt Nut Fun! But along the way it is helpful if you can be a student of good metrology lab practice, and learn what passes for data - and not - in the real world.
The biggest thing to keep in mind is your initial measurement uncertainty, as that limits the rest of your calculations. As I wrote in my Price of Chasing PPM thread - the best way to measure a precision Vref is via 732a/b, mechanical null meter and Kelvin Varley divider. Not only can you do that measure under battery power only, you get your 10Hz bandwidth limiting done for you. It's much harder to get a good .1 to 10Hz bandwidth measure from a 3458a. It can be done, but the noise the DMM adds is an issue - besides the fact a 3458a isn't really considered the best voltage transfer device for absolute measures.
And OF COURSE the best way to INCREASE measurement accuracy, DECREASE uncertainty and INCREASE measurement confidence is to
acquire more equipment So I will 100% agree with you there. More accurate equipment always helps!
Now the mark of a REALLY good Volt Nut is if their life savings is depleted buying lots of 732a/b AND they get buddies to do the same and store everything at VoltNuts house...