- ISO 4006, Measurement of fluid flow in closed conduits — Vocabulary and symbols
- ISO 5167 (all parts), Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full
- ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties
- ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)
ScopeThis International Standard establishes general principles and describes procedures for evaluating the uncertainty of a fluid flow-rate or quantity.A step-by-step procedure for calculating uncertainty is given in Annex A.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
- ISO 9300, Measurement of gas flow by means of critical flow Venturi nozzles
- ISO Guide to the expression of uncertainty in measurement (GUM), 1995
- International vocabulary of basic and general terms in metrology (VIM), 1993
3 Terms and definitionsFor the purposes of this document, the terms and definitions given in VIM (1993), GUM (1995) and the following apply.3.1uncertaintyparameter, associated with the results of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurandNote 1 to entry: Uncertainties are expressed as an absolute value and do not take a positive or negative sign.3.2standard uncertaintyu
)uncertainty of the result of a measurement expressed as a standard deviation3.3relative uncertaintyu*
expanded uncertainty divided by the best estimateNote 1 to entry: U*
can be expressed as a percentage or in parts per million.Note 2 to entry: U*
).Note 3 to entry: Relative expanded uncertainty is sometimes referred to as dimensionless expanded uncertainty.Note 4 to entry: The best estimate is in most cases the arithmetic mean of the related uncertainty interval.3.8coverage factork
numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded uncertaintyNote 1 to entry: A coverage factor is typically in the range 2 to 3.