Hi John, well, if one wanted to use a 720A, only the 0.1 and 0.01 settings are needed, so full linearity check over all decades is not needed. A second 720A to do that is not really precise enough, as the manual also states. But anyway, the preferred divider to use is the 752A.
Adrian > Gesendet: Freitag, 24. April 2015 um 16:08 Uhr > Von: "John Devereux" <[email protected]> > An: [email protected] > Betreff: Re: [volt-nuts] Advise to Junior Member Regarding Acquisition of > Fluke 5XXX Series Calibrator > > > Hi Adrian > > Oh I see... > > But... I seem to recall the 720A also, similarly, requires linearity > validation unless you just "assume" it is inherently linear? > > The manual shows a test using a second 720A! And that is "only" good to > 0.2ppm. > > John > > > > [email protected] writes: > > > Hi John, > > > > sure, seems I should have been more clear. What I wanted to say is > > that in order to have traceability starting from just a calibrated 10V > > (and 10k) standard, which is sufficient to adjust a 3458A, you still > > need some type of self-calibrating divider to validate the 3458A > > (which then, once validated, can be your working unit). Or, if one > > e.g. wants to calibrate a 5440 voltage calibrator from a 10V standard, > > you also need a divider. Assuming a non-calibrated 3458A, because of > > its highly linear ADC, can be used transferring the 10V into other > > voltage ranges, is not valid, the 3458A has a performance validation > > point that checks (within the testable limits) that the linearity is > > ok. So no way around a divider unfortunately. > > In the end, what we talk about is how do we get traceable volts > > measurement capabilities (to the 10V standard that has been > > calibrated, if one has a calibrated 1V too (of the 732A or whatever), > > less work, but the basic problem remains). > > > > Adrian > > > > > > > >> Gesendet: Freitag, 24. April 2015 um 11:43 Uhr > >> Von: "John Devereux" <[email protected]> > >> An: [email protected] > >> Betreff: Re: [volt-nuts] Advise to Junior Member Regarding > >> Acquisition of Fluke 5XXX Series Calibrator > >> > >> [email protected] writes: > >> > >> > A few things to keep in mind: > >> > - the 720A (and the 752A) are self-calibrating, i.e. you can (easily) > >> > calibrate it yourself before use. The 3458A, using its external > >> > artifact self-cal procedure based on only 10v and 10k, requires a > >> > performance verification therafter (at least every second time, see > >> > some military docs concluding this, I don't recall the link but easy > >> > to find; i would actually say, to comply with GUM, every time). > >> > >> Hi Adrian > >> > >> I don't think that this point is a fair comparison, 3458a calibration is > >> only required for absolute measurements which the 720A is incapable of > >> anyway. > >> > >> John > >> > > > > _______________________________________________ > > 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. > > > > -- > > John Devereux > _______________________________________________ > 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.
