My question is partly based on a real situation where I have 3 DMMs of decent quality Keithley 2000, 34970A (34401A), and 3457A that all agree with a good quality voltage reference that is exceeding its ppm/degree C spec as far as I am able to tell. I felt that this was telling me that I would need a 3458A to know how much closer to 10V the reference was at this point. A quick calculation of 20 bits of ADC for example told me that I was looking at 9.5 uV of resolution, or 0.6 uV at 24 bits *noise free*, etc. so it did not seem to be entirely unreasonable to see the LSD of a 6 1/2 digit DMM be higher than 1 or 2 counts.
Russ On Mon, Feb 20, 2017 at 12:57 PM, m k <[email protected]> wrote: > On 20/02/2017 18:46, Russ Ramirez wrote: > > I very much enjoy what is shared here. It has led me down the path of > > learning more about Metrology in general and the pointers to Flukecal > site > > from here are appreciated. > > > > My question is this. If I measured a 10 volt reference known to be good > to > > 8 1/2 digits, but with the LSD being > 0, assuming a transfer standard > with > > traceability and documented uncertainties etc, would a 6 1/2 digit > > voltmeter read 10.00000 volts, or round up to the limits of its AD > > converter resolution; say X uV over 10.00000 volts? > > > > I hope this is not too basic a question. > > > > Russ > > _______________________________________________ > > > Hi Russ, > > some voltmeters will supply extra digits in the output they provide, but > whether they are of any use depends upon how > stable the reference is in that particular 6.5 digit dvm, unfortunately it > needs a dvm with better capability to prove > if those digits are believable. > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
