AS 3778.2.4-2007

1 - AS 3778.2.4-2007 Measurement of water flow in open channels Part 2.4: General - Estimation of uncertainty of a flow rate measur
4 - PREFACE
5 - CONTENTS
6 - INTRODUCTION
7 - 1 Scope
7 - 2 Normative references
7 - 3 Terms and definitions
9 - 4 Symbols and abbreviated terms
9 - 4.1 Symbols
13 - 4.2 Subscripts
14 - 5 Evaluation of the uncertainty in a measurement process
15 - 6 Type A evaluations of uncertainty
15 - 6.1 General considerations
15 - 6.2 Calculation procedure
16 - 7 Type B evaluation of uncertainties
16 - 7.1 General considerations
16 - 7.2 Calculation procedure
16 - 7.3 Rectangular probability distribution
17 - 7.4 Normal probability distribution
17 - 7.5 Triangular probability distribution
17 - 7.6 Bimodal probability distribution
17 - 7.7 Assigning a probability distribution
17 - 7.8 Asymmetric probability distributions
18 - 8 Sensitivity coefficients
18 - 8.1 General
18 - 8.2 Analytical solution
18 - 8.3 Numerical solution
19 - 9 Combination of uncertainties
20 - 10 Expression of results
20 - 10.1 Expanded uncertainty
21 - 10.2 Uncertainty budget
23 - Annex A (normative) Step-by-step procedure for calculating uncertainty
23 - A. 1 Dimensional and non-dimensional uncertainty
23 - A. 2 Mathematical relationship
23 - A. 3 Standard uncertainty
24 - A. 4 Sensitivity coefficients
24 - A. 5 Combined uncertainty
24 - A. 6 Unreliable input quantities
25 - A. 7 Expanded uncertainty
25 - A. 8 Expression of results
26 - Annex B (normative) Probability distributions
28 - Annex C (normative) Coverage factors
30 - Annex D (informative) Basic statistical concepts for use in Type A assessments of uncertainty
30 - D.1 Mean of a set of data,
30 - D.2 Experimental standard deviation, s, of a set of data
31 - D.3 Degrees of freedom, ν, associated with a sample variance or standard deviation
31 - D.4 Standard uncertainty, xu, of a sample mean based on the sample standard deviation
31 - D.5 Standard uncertainty, xu, of the sample mean based on a standard deviation derived from past experience
31 - D.6 Standard uncertainty, usm, of a single value based on past experience
32 - D.7 Pooled standard deviation, spo, from several sets of data
32 - D.8 Degrees of freedom, vpo, associated with a pooled standard deviation
32 - D.9 Expanded uncertainty, xU, of a sample mean based on the sample standard deviation
33 - D.10 Expanded uncertainty, xU, of a sample mean based on a standard deviation derived from past experience
33 - D.11 Expanded uncertainty, Usm, of a single value
33 - D.12 Tolerance interval for individual measurements
34 - D.13 Detection of outliers
35 - D.14 Worked examples
42 - Annex E (informative) Measurement uncertainty sources
42 - E.1 Categories of uncertainty sources
42 - E.2 Calibration uncertainty
42 - E.3 Data acquisition uncertainty
43 - E.4 Data processing uncertainty
43 - E.5 Uncertainty due to methods
44 - Annex F (informative) Correlated input variables
46 - Annex G (informative) Examples
46 - G.1 Example 1 - A critical flow nozzle is used to measure the mass flow of air in a calibration rig
48 - G.2 Example 2 - Comparing two flow-rates measured with the same meter
53 - G.3 Example 3 - Computation of the uncertainty of flow measurement made by an orifice plate
59 - G.4 Example 4 - Computation of uncertainty in a flow (discharge) measurement made by a velocity- area survey using a current meter
61 - G.5 Example 5 - Computation of uncertainty in a flow (discharge) measurement made using weirs and flumes
64 - Annex H (informative) The calibration of a flow meter on a calibration rig
64 - H.1 General
64 - H.2 Calibration rig uncertainty
64 - H.3 Use of the calibration rig
67 - Annex I (informative) Type A and Type B uncertainties in relation to contributions to uncertainty from “random” and “systematic” sources of uncertainty
68 - Annex J (informative) Special situations using two or more meters in parallel
70 - Annex K (informative) Alternative technique for uncertainty analysis
71 - Bibliography

establishes general principles and describes procedures for evaluating the uncertainty of a fluid flow-rate or quantity.

Originated as AS 3778.2.4-1990.
Third edition 2007.