[volt-nuts] JJ standards and the 3458A

[frank.stellmach at freenet.de]

In message <52DCC9A9.7020703 at freenet.de>, Frank Stellmach writes:
>The only unsolved problem then would again be the range transfer, which >is not yet possible by cryogenic standards, afaik.
 
Change the frequency ?
 
-- Poul-Henning Kamp
| UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Poul-Henning,no that won't do it, what I meant to say:The range transfer is transfer, or measuring of voltages of 100V and 1000V range.Progammable JJ arrays deliver voltages in the range +/-12V, not much more.Therefore, increasing the driving frequency to 750Ghz or 7.5THz will not work, also serialization of 10 or 100 arrays is not feasible.So you have to divide 1kV or 100V by 100 and 10, which has to be done by normal resistive dividers, Hammon type, as cryogenic / superconducting ones for such voltages do not exist.Therefore, that voltage range is still limited to 0.5 and 0.2ppm uncertainty.As the uncertainty of comparison is limited to around 10nV, the measurement on the 1V and 100mV ranges also are uncertain to 0.01 and 0.1ppm, respectively.Even if more care and effort is spent on the Null instrument for those low volt ranges, perhaps to 1nV uncertainty, there is still a big gap to a real 9 digit DMM, with complete covering of ranges and modes.Frank

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