API MPMS 13.3 2017 pdf download.Manual of Petroleum Measurement Standards Chapter 13.3 Measurement Uncertainty.
3 Terms, Definitions, Acronyms, Abbreviations, and Symbols 3.1 Terms and Definitions For the purposes of this document, the following terms and definitions apply. Terms of more general use may be found in the API MPMS Chapter 1, Online Terms and Definitions Database. The intent is to use terms from JCGM 200:2012 (VIM) when they are available. An important point is that VIM often includes notes that more fully explain the term being defined. These notes are not shown in these definitions. The analyst is encouraged to consult with VIM to obtain a more complete understanding of the terms. 3.1.1 accuracy See measurement accuracy. 3.1.2 bias See measurement bias. 3.1.3 calibration A set of operations which establish, under specified conditions, the relationship between the values indicated by a measuring device and the corresponding known values indicated when using a suitable measuring standard. 3.1.4 confidence interval confidence range range of uncertainty The range within which the true value is expected to lie with a stated confidence level. See 4.7 for more detail. 3.1.5 confidence level The degree of confidence that may be placed on an estimated confidence interval. See 4.7 for more detail. 3.1.6 dead band (JCGM 200:2012, 4.17) Maximum interval through which a value of a quantity being measured can be changed in both directions without producing a detectable change in the corresponding indication. See related term: hysteresis. 3.1.7 degrees of freedom (JCGM 100:2008, C.2.31) dof The number of terms in a sum minus the number of constraints on the terms of the sum. 3.1.8 direct measurement (adapted from JCGM 200:2008, 2.5) Comparison of the measurand to a standard where the desired measurement is read from the standard. EXAMPLE Using a tape measure to measure the length of a measurand.
3.1.9 drift See instrumental drift. 3.1.10 elemental error source (adapted from Coleman and Steele) The most basic component within the hierarchical structure of uncertainty contributors. 3.1.11 error See measurement error. 3.1.12 given uncertainty (adapted from JCGM 200:2008, F.2.3) The numerical uncertainty and confidence interval associated with an elemental error source that has not been estimated in the course of performing the measurement under analysis. EXAMPLE One of the uncertainty specifications of a device provided by the manufacturer may be, “0.2 % of reading with a confidence level of 90 %.” If this information is used in an uncertainty analysis, then it has been “given” to the analyst rather than being experimentally determined. 3.1.13 gross error Error in procedure or an error in the execution of procedure. 3.1.14 GUM Acronym for JCGM 100:2008, Evaluation of measurement data—Guide to the expression of uncertainty in measurement, GUM 1995 with minor corrections, 2008. Sometimes referred to as “the GUM” or “the ISO GUM.” 3.1.15 hysteresis The difference between the indications of a measuring instrument when the same value of the quantity measured is reached by increasing or decreasing the quantity. EXAMPLE Given two 1-kg masses on a scale that has stabilized at 2.000 kg. If one of the masses is removed and then returned, the scale may stabilize at something other than 2.000 kg (probably low), and if another 1-kg mass is put on the scale and then removed, the scale may read something other than 2.000 kg (probably high). The differences (not necessarily equal) are due to hysteresis effects. See related term: dead band. 3.1.16 indirect measurement (adapted from JCGM 200:2008, 2.52, Example 4, Note 1) A measurement that produces a final result by calculation using results from one or more direct measurements.
3.1.19 mean The arithmetic average of a population. 3.1.20 measurand (JCGM 200:2012, 2.3) Quantity intended to be measured. 3.1.21 measurement (JCGM 200:2012, 2.1) The process of experimentally obtaining one or more quantity values that can reasonably be attributed to a quantity. 3.1.22 measurement accuracy (JCGM 200:2012, 2.13) Closeness of agreement between a measured quantity value and a true quantity value of a measurand. NOTE Accuracy is a qualitative concept; the quantitative agreement with the true value is expressed as uncertainty. 3.1.23 measurement bias (JCGM 200:2012, 2.18) Estimate of a systematic measurement error. 3.1.24 measurement error Difference between true and observed values. 3.1.25 measurement method (JCGM 200:2012, 2.5) Generic description of a logical organization of operations used in a measurement. 3.1.26 measurement model (JCGM 200:2012, 2.48) Mathematical relation among all quantities known to be involved in a measurement. 3.1.27 measurement precision (JCGM 200:2012, 2.15) Closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions.