[volt-nuts] Advise to Junior Member Regarding Acquisition of Fluke 5XXX Series Calibrator

John Devereux john at devereux.me.uk
Fri Apr 24 05:43:23 EDT 2015


acbern at gmx.de 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

> -the linearity of the 3458a is excellent and not beatable up to a 1:10
> ratio, beyond that (e.g. if you want to calibrate an instruments 1000v
> or 100mV range form a 10V reference), it is not usable, again the 720a
> or 752A are superior.
>
> So to summarize, if you want to be selfstanding, and do your
> calibrations with reference to an externally calibarted 10v and 10k
> resistor only, you need a good voltage source (5440 is hard to beat
> even by the 5720A, and can replace, with some compromises, also a 732a
> if need be), a 3458A but also some type of self-cal 1:10 and 1:100
> divider (720A or 752 or similar). You could build a hammon divider
> (1:10 and 1:100) yourself, for much less than a 720A costs, and since
> it is self-cal, if you do it right, you do not need to compromise on
> accuracy. what you really need is just the decade divide ratios to do
> all the 3458A validation, and then go from there. all the gazillion
> other ratios that the 720a offers are really not needed then.
> Adrian
>
>
>
>> Gesendet: Donnerstag, 23. April 2015 um 21:19 Uhr
>> Von: "Frank Stellmach" <frank.stellmach at freenet.de>
>> An: volt-nuts at febo.com
>> Betreff: [volt-nuts] Advise to Junior Member Regarding Acquisition
>> of Fluke 5XXX Series Calibrator
>>
>> Hi Stan,
>> 
>> the 720A can easily be replaced by an HP3458A, which is superior to the 
>> KV divider in several aspects.
>> 
>> First, the 3458A has 3-10 times better linearity, 0.02ppm (typ.) of F.S. 
>> compared to 0.1ppm of input for the 720A.
>> Therefore, a 10:1 transfer is accurate to 1ppm for the 720A only, 
>> whereas the 3458A manages 0.1 to 0.3 ppm.
>> 
>> The self calibration is much easier on the 3458A, as are all these 
>> calibration measurements, you mentioned.
>> (Fluke has published a good application note, how to replace their own 
>> old style equipment as KV, Null VM, etc. by their own 8 1/2 digit 8508A).
>> 
>> And you may get a very reasonable and recent instruments for 3000$/€, 
>> maybe much less for older ones.
>> 
>> 
>> A calibrator is limited in use, as it needs a Null VM at least.
>> 
>> Anyhow, I recommend the Fluke 5440A / 5442A DCV calibrators.
>> 
>> They are ultra stable, having 2 stacked SZ263A references inside, good 
>> for 732A stability.
>> 
>> Their D/A is also extremely linear, I measured something like 0.2ppm INL 
>> against my 3458A, and they are spec'd to 0.5ppm of output, also superior 
>> to the 720A in some volt areas.
>> 
>> They also have this handy autocal function (like the 3458A) for the 4 
>> higher volt ranges ( 11, 22, 220, 1000V),  once that they are externally 
>> calibrated, and because their internal component drift is low, after 
>> these years.
>> That means, as their internal reference is very stable, you may bring it 
>> near 24hr. specification, every time you do the autocal.
>> I could not measure any deviation to that, using my 3458A, plus a self 
>> built precision Hammon divider for 1kV.
>> 
>> Their autocal feature is not explicitely promoted, but you will find 
>> that description "between the lines" in the addendum of the user manual.
>> 
>> Only the 1V and 100mV range have to be externally calibrated quite often.
>> 
>> These instruments may cost about 2000$/€.
>> 
>> So you better have both, the 5440 and the 3458A.
>> 
>> Frank
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-- 

John Devereux


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