This part of ISO/TR 7066 describes the procedures to be used in deriving the calibration curve for any method of measuring flow rate in closed conduits or open channels, and of assessing the uncertainty associated with such calibrations. Procedures are also given for estimation of the uncertainty arising in measurements obtained with the use of the resultant graph, and for calculation of the uncertainty in the mean of a number of measurements of the same flowrate.

Only linear relationships are considered in this part of ISO/TR 7066; the uncertainty in non-linear relationships forms the subject of ISO/TR 7066-2. This part of ISO/TR 7066 is applicable, therefore, only if

a) the relationship between the two variables is itself linear, or

one or both variables can be transformed in such a manner as to create a linear relationship between them, as for instance by the use of logarithms, or

the total range can be subdivided in such a way that within each subdivision the relationship between the two variables can be regarded as being linear; and if

b) systematic deviations from the fitted line are negligible compared with the uncertainty associated with the individual observations forming the graph.

NOTE- Examples of the application of the principles contained in this part of ISO/TR 7066 are given in annexes B and C.