Guidelines For Evaluating And Expressing The Uncertainty Of Nist Measurement Results

Results of measurements and conclusions derived from them constitute much of the technical information produced by the National Institute of Standards and Technology (NIST). In July 1992 the Director of NIST appointed an Ad Hoc Committee on Uncertainty Statements and charged it with recommending a policy on this important topic. The Committee concluded that the CIPM approach could be used to provide quantitative expression of measurement that would satisfy NIST¿s customers¿ requirements. NIST initially published a Technical Note on this issue in Jan. 1993. This 1994 edition addresses the most important questions raised by recipients concerning some of the points it addressed and some it did not. Illustrations.

Results of measurements and conclusions derived from them constitute much of the technical information produced by NIST. It is generally agreed that the usefulness of measurement results, and thus much of the information that we provide as an institution, is to a large extent determined by the quality of the statements of uncertainty that accompany them. For example, only if quantitative and thoroughly documented statements of uncertainty accompany the results of NIST calibrations can the users of our calibration services establish their level of traceability to the U.S. standards of measurement maintained at NIST.

Techniques and Topics in Flow Measurement covers the applications and techniques of flow measurement. This definitive book provides guidelines for choosing appropriate techniques and assuring valid measurements as well as describes methods for treatment of calibration data in fluid flow under various conditions. The book also covers three systems of units: the SI system, the English Absolute Dimensional system, and the English Engineering system. Commonly used - and often misused - variables such as force, weight, and pressure are defined, and the relationships between the systems for these common variables are summarized. One of the many unique features of Techniques and Topics in Flow Measurement is the number of ready-to-use tables included throughout the text. Tables are provided for such commonly encountered variables as the saturation vapor pressure of water; the composition of dry air; the compressibility factor for air; air-free and air-saturated water density; viscosity of dry air, nitrogen, and other gases; and specific heat/specific volume ratios for dry air, water vapor, and moist air. Another unique feature of this book is the number of highly relevant examples. The author includes examples/exercises that demonstrate applications for density calculations; water vapor mixing ratio determination; gas viscosity interpolation; NIST guideline applications; buoyancy corrections; and more.