tailieunhanh - Uncertainty and Dimensional Calibrations by NIST J Res Nov-Dec 6 1997

The calculation of uncertainty for a measurement is an effort to set reasonable bounds for the measurement result according to standardized rules. Since every measurement produces only an estimate of the answer, the primary requisite of an uncertainty statement is to inform the reader of how sure the writer is that the answer is in a certain range. This report explains how we have implemented these rules for dimensional calibrations of nine different types of gages: gage blocks, gage wires, ring gages, gage balls, roundness standards, optical flats, indexing tables, angle blocks, and sieves | Volume 102 Number 6 November-December 1997 Journal of Research of the National Institute of Standards and Technology J. Res. Natl. Inst. Stand. Technol. 102 647 1997 Uncertainty and Dimensional Calibrations Volume 102 Number 6 November-December 1997 Ted Doiron and John Stoup National Institute of Standards and Technology Gaithersburg MD 20899-0001 The calculation of uncertainty for a measurement is an effort to set reasonable bounds for the measurement result according to standardized rules. Since every measurement produces only an estimate of the answer the primary requisite of an uncertainty statement is to inform the reader of how sure the writer is that the answer is in a certain range. This report explains how we have implemented these rules for dimensional calibrations of nine different types of gages gage blocks gage wires ring gages gage balls roundness standards optical flats indexing tables angle blocks and sieves. Key words angle standards calibration dimensional metrology gage blocks gages optical flats uncertainty uncertainty budget. Accepted August 18 1997 1. Introduction The calculation of uncertainty for a measurement is an effort to set reasonable bounds for the measurement result according to standardized rules. Since every measurement produces only an estimate of the answer the primary requisite of an uncertainty statement is to inform the reader of how sure the writer is that the answer is in a certain range. Perhaps the best uncertainty statement ever written was the following from Dr. C. H. Meyers reporting on his measurements of the heat capacity of ammonia We think our reported value is good to 1 part in 10 000 we are willing to bet our own money at even odds that it is correct to 2 parts in 10 000. Furthermore if by any chance our value is shown to be in error by more than 1 part in 1000 we are prepared to eat the apparatus and drink the ammonia. Unfortunately the statement did not get past the NBS Editorial Board and is only preserved .