I believe you can get 7-1/2 digits out of the 3457A via the HPIB port.
Regards,
Tom
----- Original Message -----
From: "Russ Ramirez" <[email protected]>
To: "Discussion of precise voltage measurement" <[email protected]>
Sent: Monday, February 20, 2017 2:26 PM
Subject: Re: [volt-nuts] Basic question concerning voltage references
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.
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