Am Sat, 6 Jun 2020 07:59:42 -0500 schrieb Steve - Home <[email protected]>:
> Along those very lines, HP/Agilent/Keysight sold both calibration > kits and verification kits for VNAs. We did a full calibration using > the mechanical calibration kit at the start of a measuring session > where you needed the absolute best accuracy your system was capable > of and used the verification kit as a sanity check during the daily > operation. > Yes, and no. Unfortunately the term "calibration" is used differently in the realms of metrology and Network Analyzers. What's typically referred to as calibration when network analyzers are concerned is aimed at canceling the effect of the environment (test leads and their frequency response, time delay/phase shift), not actual calibration of the instrument. You don't care to know how big the error introduced by that actually is, you just want to have the instrument substract it from the real measurement values. As you mention, the verification kits serve as sanity checks if the "calibration" actually was okay. But there's a number of parameters which none of the calibration and verification kits I've seen until now addresses: frequency accurracy is not checked, absolute power accurracy is not checked. Florian DH7FET > Steve > WB0DBS > > > > > On Jun 6, 2020, at 6:21 AM, Florian Teply <[email protected]> wrote: > > > > Funny thing how things work out time-wise: I had a discussion > > yesterday on the very topic during re-audit for ISO 9001. > > > > In basic terms, verification in metrology is a very slimmed down > > calibration: For a calibration, you essentially check every range of > > your instrument at usually five or more spots within that range in > > order to determine accurracy of your instrument in each range. > > For a verification, you do this only at the spot where you intend to > > measure. So if you were to measure a nominal 7.2V source, you'd > > compare the reading of your meter with your, say, known good 7.5V > > reference instead of doing a full calibration of the meter. It > > doesn't tell you anything about, say, the offset error of your > > meter, or how big the deviation is at the 1000V range, it just > > tells you if your meter meets requirements of the one measurement > > you intend to do. > > > > So, in order to determine whether or not your chinese voltage > > reference meets its specs, you'd check your meter against, say, the > > well-characterized LTZ1000A you happen to have in your lab. > > > > Strictly speaking, you still have to do it as carefully as you > > would do a real calibration, taking all known effects into account, > > but it's still much less time-consuming than a full calibration as > > you check only one single point instead of all possible ranges with > > five points each. > > > > Does this help answer your questions or did I just bring up more > > questions than answers? > > > > best regards, > > Florian > > > > > > Am Wed, 3 Jun 2020 09:58:59 +0100 > > schrieb "Dr. David Kirkby" <[email protected]>: > > > >> I am trying to work out what the BIPM definition of verification > >> means > >> > >> https://jcgm.bipm.org/vim/en/2.44.html > >> > >> “ provision of objective evidence that a given item fulfils > >> specified requirements” > >> > >> Let’s assume that I wanted to verify if the voltage reference meets > >> the Chinese specifications. Would consulting the 3457A manual and > >> voltage reference specifications, to determine if the meter is good > >> be considered verification? > >> > >> Or does verification only apply to an instrument? For example > >> comparing the 3457A to a Fluke voltage reference? > >> > >> The one sentence definition in VIM leaves me wondering what the > >> intension of the entry is. > >> > >> > >> > >> > > > > > > _______________________________________________ > > volt-nuts mailing list -- [email protected] > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and > > follow the instructions there. > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and > follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
