Measurement of fluid flow – Procedures for the evaluation of uncertainties ISO 5168 - 2005

ISO 5168:2005 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.
 

Whenever a measurement of fluid flow (discharge) is made, the value obtained is simply the best estimate that can be obtained of the flow-rate or quantity. In practice, the flow-rate or quantity could be slightly greater or less than this value, the uncertainty characterizing the range of values within which the flow-rate or quantity is expected to lie, with a specified confidence level.
GUM is the authoritative document on all aspects of terminology and evaluation of uncertainty and should be referred to in any situation where this International Standard does not provide enough depth or detail. In particular, GUM (1995), Annex F, gives guidance on evaluating uncertainty components.