Electronics > Metrology

Another method to get a precision voltage reference / does it make sense

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pelule:
Just read a thread in [volts-nuts] regarding the US patent 6091281 (attached)
https://www.mail-archive.com/volt-nuts@febo.com/msg03027.html
Thought a bit about it:
1 - use a rubidium based GPSDO (I just working one)
 +  the rubidium deliveres a high short term stability
 + the GPSDO deliveres long term stability/accuracy
 == quite good reference frequency
2 - yet unclear for me
  ? what kind of VCO to use
  ? does ait really need high lineary (my guess not, but good short term stability)
  ? need good (low) long term drift

Does that approach make sense?
It seems worth to give em a try.

Vgkid:
I will say that that was a rather interesting bunch of posts to read through.

pelule:
Yepp, I also followed that intersting thread. That 400k$ is far, far out of my scope, even I also own a 3458A and a Datron 1281.
My thought during reading that thread was:
If I don't need it for cal business (with return of investment), there would be a cheaper way fitting my needs.
F. e. buy a quite good voltage reference (f. e. Fluke 732B, say cost is 5k$) and let calibrate it regular, let say 10 times a year.
Assuming a good qual cal lab ask 1k$, it could be done >300 times for the same amount of money.
if cal is done 10 times a year, that means 30 years cal history data - a good statistical basis.

Regarding the "another method" - had same thougth, that's why I have noted questions to answer:
  ? does it really need high lineary (my guess not, but good short term stability)
  ? need good (low) long term drift
I fully agree, the drift (time, temp. humidity) are in any case the main quality criterias for any reference.
As anything is drifting, this "reference" would drift also. Just how much is the question.
If a drift below 2ppm/yr is realistic it would worth to to try.

branadic:
I can say nothing about the presented approach, but the question is, what are you really looking for? Do you really need the VOLT inside your homelab or do just want to know what's the real output of your voltage reference?

I know about activities realizing the latter. That means setting up a measuring system allowing you to precisely measure voltages without the need of an ADC + voltage reference by precisely measuring E-fields. I can't go into details, as all this is very novel and at the very beginning and far away from being integrated into a small device yet.

pelule:
@branadic
My interest is just "interest" and "shall I try to build one" for fun in working on precision analog.
I am just finishing my Rubidum based GPSDO - and have seen that thread.

I don't need "the VOLT" and have no urgent need to know the real output of my voltage references.
I regular test my meters against my references (Guildline:9152T/P4, HP735) just to detect potential issues, I also log the meaures for high drifts detection (fully accepting the increasing uncertainty).
It's the typical men with two clocks problem - just I don't need the exact time, I just like to know, if the clock are operating.
My 3458A got the last cal 6 month ago - that's my "reference".
The measure logs show less than 0.2ppm/yr difference of the 1281 against the in-cal 3458A.

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