In the case the lab in question was accredited and we went through the audits of process and procedure and go through them to this day and we have the nice certs on the wall.
When LORAN went away we then had to use very expensive processes to MAINTAIN that traceability and accreditation which LORAN provided very inexpensively for many years. And it would be really nice to be able to replicate the low cost of LORAN based legal metrology that with what we have today which is GPS We have a few GPSDO's but they are not connected as currently worthless for legal metrology we have a couple of 5071's which get shipped under power to another lab for legal traceability It was a lot easier and cheaper back when a couple of SRS LORAN units and our record keeping and a annual process audit was all that was required to maintain legal traceability Sent from my iPhone On Jun 1, 2013, at 6:19 PM, "Charles P. Steinmetz" <[email protected]> wrote: > > Bob wrote: > >>> At least the way I read the pdf's NIST seems to believe that GPS is legally >>> traceable to NIST. It is the same "measure and then look up the data" sort >>> of thing that LORAN used to be. Took a while to read through them all… > > Yes, that is correct. > > Magnus wrote: > >> However, just taking time from GPS does not achieve NIST traceability. >> * * * >> You can achieve NIST traceability (or to any other NIH) if you do a whole >> bunch of things _right_ and in accordance with relevant standards. Few do. > > That is also correct. Instruments are *not* "NIST traceable." However, a > measurement made with the equipment can be "NIST traceable" under certain > conditions. It is the PROCESS that produces traceability. (I use "NIST" > here for convenience -- any National Metrology Institute can be substituted.) > > Sadly, you are also correct that few do the process right. In my experience, > about 80% of labs that claim they are calibrating frequency-measuring > equipment to "NIST-traceable" standards really aren't. (I've had this rather > adversarial discussion with several dozen lab managers over the years.) Of > course, this does not mean their calibrations are not accurate, just that, > from the standpoint of legal metrology, the instruments they calibrate cannot > be used to make NIST-traceable measurements or perform NIST-traceable > calibrations. (When it comes to all of the "NIST calibrated" equipment you > see on ebay, the figure approaches 100% very, very closely.) > > The same is true the other way around. You can have all of your equipment > calibrated by a lab that works to NIST-traceable standards, but if you do not > follow through with the traceability process the measurements you make with > those instruments (including calibrations done using them) will not be > NIST-traceable, from a legal metrology perspective. > > Think of the traceability process as a chain. One broken link and > traceability vanishes. > > One of the required criteria for traceability is *demonstrated competence*. > Generally, this is done by becoming accredited to the relevant ISO/IEC > standard by an accreditation body. No matter how sophisticated and > meticulous someone is, if their lab is not accredited, they cannot make NIST > traceable measurements or perform NIST-traceable calibrations. Period. This > is where home labs and other "little guys" inevitably fail to preserve > traceability. Again, this does not mean that their measurements or > calibrations are junk -- just that they are not NIST-traceable, as far as > legal metrology is concerned. The A2LA shows you what you need to do (see > link in my last e-mail). > > The OP may have thought he was making NIST-traceable measurements using WWVB > and/or LORAN standards. But if his lab was not accredited, that was not so. > Nothing has changed, in that regard, with the advent of GPSDOs (except that > the uncertainty levels are better now). > > Best regards, > > Charles > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
