ISO/TR 11974:1997

Measurement of liquid flow in open channels — Electromagnetic current meters

Mesure de débit des liquides dans les canaux découverts — Moulinets électromagnétiques

General Information

• Status: Withdrawn
• Publication Date: 17-Dec-1997
• Withdrawal Date: 17-Dec-1997
• ICS: 17.120.20 - Flow in open channels
• Technical Committee: ISO/TC 113/SC 5 - Instruments, equipment and data management
• Drafting Committee: ISO/TC 113/SC 5 - Instruments, equipment and data management
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 03-Feb-2005

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 11974
First edition
1997-12-15
Measurement of liquid flow in open
channels — Electromagnetic current meters
Mesure de débit des liquides dans les canaux découverts — Moulinets
électromagnétiques
A
Reference number
ISO/TR 11974:1997(E)

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ISO/TR 11974:1997(E)
Contents Page
1 Scope . 1
2 Normative reference . 1
3 Definitions . 1
4 Principle of operation . 1
Electromagnetic current meters.
5 3
6 Operational aspects. 4
7 Calibration. 4
8 Maintenance . 5
9 Transport and storage . 5
Log book.
10 5
©  ISO 1997
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ii

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©
ISO ISO/TR 11974:1997(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International
Standards, but in exceptional circumstances a technical committee may
propose the publication of a Technical Report of one of the following types:
— type 1, when the required support cannot be obtained for the
publication of an International Standard, despite repeated efforts;
— type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility of
an agreement on an International Standard;
— type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International Standard
(“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they can be transformed into International
Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or
useful.
ISO/TR 11974, which is a Technical Report of type 2, was prepared by
Technical Committee ISO/TC 113, Hydrometric determinations, Subcom-
mittee SC 5, Instruments, equipment and data management.
This document is being issued in the Technical Report (type 2) series of
publications (according to subclause G.3.2.2 of part 1 of the ISO/IEC
Directives, 1995) as a “prospective standard for provisional application” in
the field of hydrometric determinations because there is an urgent need for
guidance on how standards in this field should be used to meet an
identified need.
This document is not to be regarded as an “International Standard”. It is
proposed for provisional application so that information and experience of
its use in practice may be gathered. Comments on the content of this
document should be sent to the ISO Central Secretariat.
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©
ISO/TR 11974:1997(E) ISO
A review of this Technical Report (type 2) will be carried out not later than
three years after its publication with the options of: extension for another
three years; conversion into an International Standard; or withdrawal.
Annex A of this Technical Report is for information only.
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©
TECHNICAL REPORT  ISO ISO/TR 11974:1997(E)
Measurement of liquid flow in open channels —
Electromagnetic current meters
1  Scope
This Technical Report specifies the operational requirements, construction, calibration and maintenance aspects of
a solid-state electromagnetic current meter for the single-point measurement of velocity of electrically conducting
liquids, including water.
2  Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this
Technical Report. At the time of publication, the edition indicated was valid. All standards are subject to revision,
and parties to agreements based on this Technical Report are encouraged to investigate the possibility of applying
the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently
valid International Standards.
ISO 772:1996, Hydrometric determinations — Vocabulary and symbols.
3  Definitions
For the purposes of this Technical Report, the definitions given in ISO 772 apply.
4  Principle of operation
The principle of operation of the electromagnetic current meter is illustrated in figure 1 and is based on the Faraday
generator effect, which may generally be stated as follows:
“. when there is a perpendicular component of relative motion between an electrical conductor and a magnetic
field, an electrical potential is induced in that conductor. The magnitude of the electrical potential is proportional
to the velocity at which the conductor moves relative to the electromagnetic field.”
1

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ISO
ISO/TR 11974:1997(E)
Key:
B  Lines of force of magnetic field
l  Distance between electrodes
U  Induced voltage
v  Velocity of water
Figure 1 — Electromagnetic flow meter
The relationship can be expressed as:
. . . (1)
Ef=()vFB
where
E is the electrical potential, in volts;
v is the velocity, in metres per second;
F is the shape factor of the electromagnetic field, in metres;
B is the magnetic field strength, in teslas.
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ISO
ISO/TR 11974:1997(E)
Since F and B are fixed, and can therefore be taken as constants, v can be expressed in terms of E, so that:
vK= E (m / s) . . . (2)
where K is a calibration factor.
It is conceivable that the calibration may be affected if the strength and shape of the generated field is interrupted or
distorted in close proximity to the water/air or water/channel interface. Where this question arises, guidance should
be sought from the manufacturer.
5  Electromagnetic current meters
5.1  General
An electromagnetic current meter has no moving parts and consists of a probe, with solid-state encapsulated
circuitry and electromagnetic sensor, a control
...