J
jfgunn
I thought this was a topic I understood well but hav begun to doubt myself when I look at some other calibration certificates.
Take the calibration of a 1" micrometer at 1" that reads by 0.001"
The uncertainty of this calibration using gage blocks is roughly 0.0006". 1/2 the resolution of the micromter is the dominant factor.
The accuracy of a 1" mictometer is 0.001". I would say that I do not meet a 4:1 TUR because 0.001"/0.0006" is 1.67. My TUR is 1.67.
When I read the definition from the Metrology Handbook it says that TUR = (UUT Tolerance / STD Uncertainty).
This might lead me to believe that the TUR would be 0.001"/0.000010" = 100 where 0.000010" is roughly the accuracy of a 1" gage block.
This question comes up when I read calibration certificates from accredited labs that says " uness otherwise noted, we meet a 4:1 TUR....".
By my definition, any calibration certificate with this wording would have to report the uncertainty on every certficate where the accuract of the unit under test is equal to 1 division. (ie most weighing scales, micrometers, etc..)
For certificatges I issue, I have used a more stingent definition of the term which would lead me to provide a good calibration certificate to my cusromer either way.
I would apprecaite any thoughs on the topic.
Take the calibration of a 1" micrometer at 1" that reads by 0.001"
The uncertainty of this calibration using gage blocks is roughly 0.0006". 1/2 the resolution of the micromter is the dominant factor.
The accuracy of a 1" mictometer is 0.001". I would say that I do not meet a 4:1 TUR because 0.001"/0.0006" is 1.67. My TUR is 1.67.
When I read the definition from the Metrology Handbook it says that TUR = (UUT Tolerance / STD Uncertainty).
This might lead me to believe that the TUR would be 0.001"/0.000010" = 100 where 0.000010" is roughly the accuracy of a 1" gage block.
This question comes up when I read calibration certificates from accredited labs that says " uness otherwise noted, we meet a 4:1 TUR....".
By my definition, any calibration certificate with this wording would have to report the uncertainty on every certficate where the accuract of the unit under test is equal to 1 division. (ie most weighing scales, micrometers, etc..)
For certificatges I issue, I have used a more stingent definition of the term which would lead me to provide a good calibration certificate to my cusromer either way.
I would apprecaite any thoughs on the topic.