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AS 3778.3.4:2022
$143.28
Measurement of water flow in open channels, Part 3.4: Velocity-area methods — Collection and processing of data for determination of uncertainties in measurement (ISO 1088:2007, IDT)
AS 3778.3.4:2022 identically adopts ISO 1088:2007, which specifies requirements for the collection and processing of data for the determination of the uncertainties in measurements of discharge in open channels by velocity-area methods using current meters.
Table of contents
Header
About this publication
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Symbols and abbreviated terms
4 Types of errors and procedure for estimating the uncertainties in flow measurement
4.1 Principle
4.2 Occurrence of error
4.3 Sources of error
4.4 Determination of the individual components of the uncertainty
4.4.1 Uncertainties in width
4.4.2 Uncertainties in depth
4.4.3 Uncertainties in the determination of the mean velocity
4.5 Total uncertainty in discharge
5 Collection and processing of data for the investigation of component uncertainties – type A evaluation of uncertainties
5.1 Data on the local point velocity
5.2 Data on the average velocity
5.2.1 General
5.2.2 Location of the verticals
5.2.3 Distribution of measuring points in the vertical
5.2.4 Period of measurement of local point velocities
5.2.5 Number of measurements
5.2.6 Presentation of data
5.3 Data on the velocity-area method
5.3.1 General
5.3.2 Measurement at 0,6 times the depth
5.3.3 Velocity-distribution method
5.3.4 Presentation of data
5.3.5 General data
5.4 Integration method
5.5 Calibration curves
5.6 Distance measurements
5.7 Depth measurements
6 Data processing
6.1 General
6.2 Error-type i
6.2.1 Finite measuring time and distribution of results
6.2.2 Correction for non-steady conditions
6.2.3 Standard deviation of velocity fluctuations
6.2.4 Autocorrelation function
6.2.5 Effect of measuring time on standard deviation (1)
6.2.6 Effect of measuring time on standard deviation (2) (See also Annex B)
6.2.7 Compilation of results
6.3 Error-type ii – Approximation of mean velocity in the vertical
6.3.1 General
6.3.2 Determination of the standard mean velocity in the vertical
6.3.3 Computation methods
6.3.4 Sampling error due to velocity fluctuations and computation rule
6.3.5 Sampling error due to computation rule
6.4 Error-type iii – Limited number of verticals
6.4.1 General
6.4.2 True discharge
6.4.3 Omission of verticals
6.4.4 Mean and standard deviations of error
6.4.5 Criteria applied in choosing the verticals (See also Annex F)
Annex A
Annex B
Annex C
C.1 General data on the river during measuring period
C.2 General data on measuring verticals
C.3 Method of velocity measurement (Please tick as appropriate)
C.4 Measuring apparatus
C.5 Measurements at verticals
C.5.1 Vertical at maximum depth
C.5.1.1 General data
C.5.1.2 Description of bed conditions
C.5.1.3 Velocity observations
C.5.2 Vertical at 0,6 times the maximum depth
C.5.3 Vertical at 0,3 times the maximum depth
Annex D
D.1 General data on the river during measuring period
D.2 Method of velocity measurement (Please tick as appropriate)
D.3 Measuring apparatus
D.4 Measurements at verticals
D.4.1 Vertical at maximum depth
D.4.1.1 General data
D.4.1.2 Description of bed conditions
D.4.1.3 Velocity observations
D.4.2 Vertical at 0,6 times the maximum depth
D.4.3 Vertical at 0,3 times the maximum depth
Annex E
E.1 General data on the river during measuring period
E.2 Method of velocity measurement (Please tick as appropriate)
E.3 Measuring apparatus
E.4 General data on velocity measurement
E.4.1 Velocity observations
E.4.2 Description of bed conditions
E.5 Method of measurement of mean velocity at verticals (Please tick as appropriate)
Annex F
Annex G
G.1 General
G.2 Uncertainties in width (ub)
G.3 Uncertainties in depth (ud)
G.4 Uncertainties in determination of the mean velocity
