good point In a message dated 9/17/2017 2:01:01 P.M. Eastern Daylight Time, jimlux@earthlink.net writes: On 9/17/17 9:42 AM, KA2WEU--- via time-nuts wrote: > Simply call it " Make it to meet specification", N1UL > > > In a message dated 9/17/2017 12:39:32 P.M. Eastern Daylight Time, > magnus@rubidium.dyndns.org writes: > > Hi, > > The word "calibration" is overloaded with multiple meanings, and > incompatible too. > <snip> > "calibration" can thus imply different things. > > I regularly see people use these terms inconsistently. That people get > disappointed when they get the wrong thing is to be expected. > > Cheers, > Magnus > Indeed - in my business, we have to be careful about the word "test" vs, say, "characterization". A "test" has a pass/fail criteria associated with it, while a "characterization" might just need recording what the value is. "tests" have institutional requirements for witnessing, etc. that "characterizations" do not, for instance. And this gets into the whole "knowledge" vs "control" - I may not care if a XO changes frequency 10ppm over temperature, as long as it's repeatable and I can know the actual frequency within 0.5 ppm. As Magnus points out, "calibration" can mean many different things, and some of them are historically derived. Back in the day, there may have been some sort of physical adjustment required to, for instance, set the scale factor of a display - but now, it's "calibrated by design", and the "calibration process" (as in "sending it to the cal lab" to get a "cal cert") is more about verification that it's not "broken". I also used to (and still do) get bent out of shape when you'd send something like a power supply out for cal, and it would come back with some problem (like a non-functioning pilot light). And the cal lab would say: "we checked the output voltage and it is within spec". Yeah, but isn't "proper function of all features" covered - and the response would be "no, it is not, we don't see 'verify function of pilot light' on the cal procedure we have" ANd then there's the "calibration/validation" phase of instruments in space - that's a completely different kind of thing, more akin to characterization.. The 'val' part is yes, verifying that the instrument is working as designed,but the 'cal' part is more about relating instrument measurements to some other reference, and from that, relating it to some physical property of interest. And that can happen at many levels. A spaceborne scatterometer to measure winds can be cal/val at 1) Does the instrument work, and are the instrumental effects accounted for - if it measure a particular backscatter cross section, is that what the backscatter cross section really is? 2) Does the "retrieval model function" that turns backscatter measurements into wind speed and direction work? And particularly for #2, a lot of it is inferential - comparing one model against another, since there's not really "ground truth" available. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.