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AS 3778.4.2:2022
[Current]Measurement of water flow in open channels, Part 4.2: Measurement using flow gauging structures — Rectangular broad-crested weirs (ISO 3846:2008, IDT)
AS 3778.4.2:2022 identically adopts ISO 3846:2008, which specifies requirements for the use of rectangular broad-crested weirs for the accurate measurement of flow of clear water in open channels under free flow conditions.
Published: 10/06/2022
Pages: 29
Table of contents
Cited references
Content history
Table of contents
Header
About this publication
Preface
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Installation
5.1 General
5.2 Selection of site
5.3 Installation conditions
5.3.1 General
5.3.2 The approach channel
5.3.3 The measuring structure
5.3.4 Downstream of the structure
6 General maintenance requirements
7 Measurement of head(s)
7.1 General
7.2 Stilling or float well
7.3 Zero setting
8 Rectangular broad-crested weirs
8.1 Specification for the standard weir
8.2 Location of the head gauge section
8.2.1 Upstream head measurement
8.2.2 Downstream head measurement
8.3 Provision for modular flow
9 Discharge relationships
9.1 Modular flow discharge equation
9.2 Modular coefficient of discharge
9.3 Limitations for operation in the modular flow range
9.4 Drowned flow discharge equation
9.5 Limitations for operation in the drowned flow range
10 Uncertainties in flow measurement
10.1 General
10.2 Statement of the uncertainty of a flow measurement in a channel
10.2.1
10.2.2
10.3 Combining measurement uncertainties
10.4 Uncertainty of discharge coefficient u(C) for the broad-crested weir
10.4.1 General
10.4.2 Modular flow measurement uncertainty
10.4.3 Drowned flow measurement uncertainty
10.5 Uncertainty budget
11 Example
11.1 General
11.2 Characteristics — Gauging structure
11.3 Characteristics — Gauged head instrumentation
11.4 The discharge coefficient
11.5 The discharge estimate
11.6 Uncertainty statement
11.6.1
11.6.2
11.6.3
11.6.4
11.6.5
11.6.6
Annex A
Annex B
Annex C
C.1 General
C.2 Confidence limits and coverage factors
C.3 Random and systematic error
C.4 Measurement standards
C.5 Evaluation of Type-A uncertainty
C.6 Evaluation of Type-B uncertainty
C.6.1 General
C.6.2 The triangular distribution
C.6.3 The rectangular distribution
C.6.4 The normal probability distribution
C.6.5 The bimodal probability distribution
C.7 Combined uncertainty value, uc
Annex D
Bibliography
Cited references in this standard
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