SIST ISO 3455:2021

INTERNATIONAL ISO
STANDARD 3455
Third edition
2021-01
Hydrometry — Calibration of current-
meters in straight open tanks
Hydrométrie — Étalonnage des moulinets en bassins découverts
rectilignes
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle of calibration . 1
4.1 Statement of the principle . 1
4.2 Accuracy of the method . 2
4.2.1 Overall uncertainty on the velocity measurement . 2
4.2.2 Requirements for accurate measurements . 2
5 Infrastructure . 2
5.1 Dimensions of the towing tank . 2
5.1.1 General. 2
5.1.2 Length. 2
5.1.3 Depth and width . 2
5.2 Towing cart . 3
5.2.1 General. 3
5.2.2 Cart track system . 3
5.2.3 Types of towing carts . 3
5.2.4 Cart operation . 3
5.2.5 Cart control . 4
5.3 Measuring equipment . 4
5.3.1 General. 4
5.3.2 Distance measurement . 4
5.3.3 Time measurement . 4
5.3.4 Current-meter velocity measurement . 4
5.3.5 Sources of error related to infrastructure . 5
5.4 Data acquisition . 6
5.5 Data processing . 6
5.6 Other requirements . 6
6 Calculation of uncertainty . 6
7 Calibration procedure . 7
7.1 Calibration of rotating element current-meters . 7
7.1.1 Suspension of the current-meter . 7
7.1.2 Performance of calibration . 7
7.1.3 Data analysis . 8
7.1.4 Presentation of results . 9
7.2 Calibration of electromagnetic current-meters .10
7.2.1 Instructions for calibration .10
7.2.2 Mounting the electromagnetic current-meter .10
7.2.3 Number of calibration points .10
7.2.4 Performance of calibration .11
7.2.5 Data analysis .11
7.2.6 Presentation of results .11
7.3 Calibration of acoustic current-meters for point velocity measurement .11
7.3.1 Instructions for calibration .11
7.3.2 Mounting the acoustic current-meter .12
7.3.3 Performance of calibration .12
7.3.4 Data analysis .12
7.3.5 Presentation of results .12
Bibliography .13
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 5,
Instruments, equipment and data management.
This third edition cancels and replaces the second edition (ISO 3455:2007), which has been technically
revised.
The main changes compared to the previous editions are as follows:
— a subclause for calibration of acoustic current-meters for point velocity measurement has been added;
— clauses referring to outdated tracking systems like track systems using tooth belts have been
removed;
— clauses referring to outdated technique for data acquisition like strip chart recorder or magnetic
tapes have been removed;
— the clause for computerized data acquisition and processing system has been removed;
— the clause discussing the Epper effect has been removed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 3455:2021(E)
Hydrometry — Calibration of current-meters in straight
open tanks
1 Scope
This document specifies a calibration method for mechanical type, electromagnetic type and acoustic
type hydrometric current-meters used for point velocity measurement of flowing water. The method
requires towing the instrument through still water in a straight open tank. It includes measuring
apparatus, the calibration procedure, the method of presenting the results and the uncertainties
associated with the method.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 772, Hydrometry — Vocabulary and symbols
ISO 2537, Hydrometry — Rotating-element current-meters
ISO/IEC Guide 98-3Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 772 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Principle of calibration
4.1 Statement of the principle
Calibration of a current-meter means experimental determination of the relationship between water
velocity and either the rate of revolution of the rotating
...