[volt-nuts] What is Transfer Accuracy?
frank.stellmach at freenet.de
Sun May 4 13:41:49 EDT 2014
this term is quite fixed.
You will find that specification for all "premium" instruments; where
this parameter is lacking, it's no good instrument, either.
It describes, how precisely one can compare two different artefacts
against each other.
As an example, you want to transfer the "accuracy" of a 732B 10V
standard to your home standard.
The transfer accuracy of an HP3458A specifies 0.1ppm accuracy within 10
minutes and 0.5°C.
That means, your home standard will be be measured within 0.1ppm
compared to the 732B, and that, despite the fact that the 3459A in all
other stability/accuracy figures is about an order of magnitude worse.
This is also valid for non-equal values, i.e. if you compare 7,2V
(directly out of a LTZ1000) against10V from the 732B, and that's due to
the ultra high linearity of the 3458A (typ. 0.02ppm).
It's a pity, that for this instrument the Ohm function transfer
stability is not specified.
I tried to specify it on my own by external very stable resistors
(VHP202Z), which were temperature stabilized or temperature-measured.
And I got about 0.2ppm within 10min and 0.2°C.
But in the end, what I am also missing, is an official document or
procedure, how this transfer accuracy is to be measured correctly /
Perhaps somebody can name a source for that, perhaps at NIST?
Same goes for the definition of linearity, integral and differential,
I also had to guess that, when I measured the linearity of my 5442B.
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