SIST EN 17694-1:2023
(Main)Hydrometry - Minimum performance requirements and test procedures for water monitoring equipment - Devices for the determination of flow - Part 1: Open channel instrumentation
Hydrometry - Minimum performance requirements and test procedures for water monitoring equipment - Devices for the determination of flow - Part 1: Open channel instrumentation
This European standard specifies general requirements, minimum performance requirements and test procedures for open channelinstrumentation used to determine either volumetric flow-rate and/or total volume passed of waters in artificial open channels. Itcovers the following technology categories:
−Level sensors with associated electronics designed to be used with a conventional gauging structure (e.g. weir or flumefor which the stage discharge characteristics are established and published in a national or international standard) or afluid velocity sensor.
−Integrated velocity area devices comprising level and velocity sensors that may be separate or combined in a single assembly;
−Velocity sensors that determine the mean water velocity through a channel.
It is recognised that for some OCIs certain tests cannot be carried out.
Hydrometrie - Leistungsanforderungen und Prüfverfahren für Wasserüberwachungsgeräte - Geräte zur Bestimmung des Durchflusses - Teil 1: Messgeräte für offenes Gerinne
Dieses Dokument legt allgemeine Anforderungen, Mindest-Leistungsanforderungen und Prüfverfahren für Messgeräte für offene Gerinne fest, die für die Bestimmung des Volumenstroms und/oder des Gesamtdurchflussvolumens von Wasser in künstlichen offenen Gerinnen verwendet werden. Es behandelt die folgenden technischen Kategorien:
- Wasserstandssensoren mit zugehöriger Elektronik, die für die Verwendung mit herkömmlichen Pegelbauwerken ausgelegt sind. (Die Anforderungen und Prüfverfahren für Pegelbauwerke wie etwa Wehre und Messgerinne sind ausgeschlossen. Die Durchflusskurven für zahlreiche dieser Bauwerke sind in nationalen und internationalen Normen festgelegt und veröffentlicht.)
- Fließgeschwindigkeitssensoren.
Integrierte Flächengeschwindigkeitsmessgeräte mit Wasserstands- und Fließgeschwindigkeitssensoren, die voneinander getrennt oder in einer Baugruppe zusammengefasst sein dürfen.
- Fließgeschwindigkeitssensoren, die die mittlere Fließgeschwindigkeit des Wassers durch ein Gerinne bestimmen.
Es ist bekannt, dass bestimmte Prüfungen für einige OCIs nicht durchgeführt werden können.
Hydrométrie - Exigences minimales de performance et modes opératoires d'essai pour les équipements de surveillance de l'eau - Dispositifs de mesure de l'écoulement - Partie 1 : Instruments de mesure pour écoulements à surface libre
Le présent document spécifie les exigences générales, les exigences minimales de performance et les modes opératoires d'essai applicables aux instruments de mesure des écoulements à surface libre utilisés pour déterminer le débit volumétrique et/ou le volume total écoulé des eaux dans les canaux artificiels à surface libre. Il couvre les catégories technologiques suivantes :
- les capteurs de niveau avec électronique associée, conçus pour être utilisés avec une structure hydrométrique conventionnelle. (Les exigences et les modes opératoires d'essai applicables aux structures hydrométriques, telles que les déversoirs et les canaux jaugeurs, sont exclus. Les caractéristiques hauteur-débit de bon nombre de ces structures sont établies et publiées dans des normes nationales et internationales) ;
- les capteurs de vitesse de fluide.
Il s’agit de dispositifs intégrés d'exploration du champ des vitesses comportant des capteurs de niveau et des capteurs de vitesse, qui peuvent être séparés ou combinés en un seul ensemble ;
- les capteurs de vitesse qui déterminent la vitesse moyenne de l'eau dans un canal.
Il est reconnu que certains essais ne peuvent pas être effectués sur certains OCI.
Hidrometrija - Minimalne zahteve za tehnične lastnosti in preskusni postopki za opremo za nadzor vode - Naprave za ugotavljanje pretoka - 1. del: Instrumenti z odprtim kanalom
Ta evropski standard določa splošne zahteve, minimalne zahteve glede zmogljivosti in preskusne postopke za instrumente z odprtim kanalom, ki se uporabljajo za določanje stopnje volumetričnega pretoka in/ali celotne količine pretoka vode v umetno odprtih kanalih. Zajema naslednje tehnološke kategorije:
− senzorje ravni s povezano elektroniko, ki so zasnovani za uporabo s standardno merilno konstrukcijo (npr. jez ali kanal, za katerega so določene karakteristike stopenjskega izpusta in objavljene v nacionalnem ali mednarodnem standardu) ali senzor hitrosti pretoka;
− vgrajene območne naprave za ugotavljanje pretoka, ki vključujejo senzorje ravni in hitrosti, ki so lahko ločeni ali povezani v en sklop;
− senzorje hitrosti, ki določajo povprečno hitrost pretoka vode skozi kanal.
Znano je, da nekaterih preskusov instrumentov z odprtim vodom (OCI) ni mogoče izvesti.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 17694-1:2023
01-julij-2023
Hidrometrija - Minimalne zahteve za tehnične lastnosti in preskusni postopki za
opremo za nadzor vode - Naprave za ugotavljanje pretoka - 1. del: Instrumenti z
odprtim kanalom
Hydrometry - Minimum performance requirements and test procedures for water
monitoring equipment - Devices for the determination of flow - Part 1: Open channel
instrumentation
Hydrometrie - Leistungsanforderungen und Prüfverfahren für
Wasserüberwachungsgeräte - Geräte zur Bestimmung des Durchflusses - Teil 1:
Messgeräte für offenes Gerinne
Hydrométrie - Exigences minimales de performance et modes opératoires d'essai pour
les équipements de surveillance de l'eau - Dispositifs de mesure de l'écoulement - Partie
1 : Instruments de mesure pour écoulements à surface libre
Ta slovenski standard je istoveten z: EN 17694-1:2023
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
17.120.20 Pretok v odprtih kanalih Flow in open channels
SIST EN 17694-1:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 17694-1:2023
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SIST EN 17694-1:2023
EN 17694-1
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2023
EUROPÄISCHE NORM
ICS 07.060; 17.120.20
English Version
Hydrometry - Minimum performance requirements and
test procedures for water monitoring equipment - Devices
for the determination of flow - Part 1: Open channel
instrumentation
Hydrométrie - Exigences minimales de performance et Hydrometrie - Leistungsanforderungen und
modes opératoires d'essai pour les équipements de Prüfverfahren für Wasserüberwachungsgeräte - Geräte
surveillance de l'eau - Dispositifs de mesure de zur Bestimmung des Durchflusses - Teil 1: Messgeräte
l'écoulement - Partie 1 : Instruments de mesure pour für offenes Gerinne
écoulements à surface libre
This European Standard was approved by CEN on 13 February 2023.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17694-1:2023 E
worldwide for CEN national Members.
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SIST EN 17694-1:2023
EN 17694-1:2023 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols. 8
5 Principle . 9
6 General requirements . 10
6.1 Requirements for open channel instrumentation . 10
6.2 Requirements for associated documentation . 11
7 Performance requirements . 12
7.1 Expression of performance requirements . 12
7.2 Performance requirements . 13
7.3 Computational accuracy . 15
7.4 Data retention . 15
7.5 Environmental requirements . 15
7.6 Water temperature requirements . 16
7.7 Installation influences. 16
7.8 Field test requirements . 16
8 Testing . 16
8.1 General requirements for testing . 16
8.2 Laboratory test conditions . 17
8.3 Reporting . 18
9 Laboratory test procedures . 18
9.1 Guidance for establishing a test plan . 18
9.2 Verification by inspection . 19
9.3 Performance tests . 20
9.3.1 Loss of power for electronic OCIs . 20
9.3.2 Bias and repeatability . 20
9.3.3 Supply voltage . 20
9.3.4 Output impedance . 21
9.3.5 Water temperature . 21
9.3.6 Ambient air temperature and relative humidity . 21
9.3.7 Direct solar radiation . 23
9.3.8 Sensor location . 24
9.3.9 Incident light . 24
9.3.10 Accuracy of computation . 25
9.3.11 Effect of channel size . 26
9.3.12 Response time . 26
10 Field test procedures . 27
10.1 Objectives of field test . 27
10.2 Field test plan . 27
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10.3 Field test requirements . 27
10.4 Error under field test conditions . 28
10.5 Up-time . 28
10.6 Maintenance . 29
Annex A (normative) Evaluation of test data . 30
A.1 Introduction . 30
A.2 Bias . 30
A.3 Repeatability . 31
A.4 Effect of influence quantities . 31
A.5 Combined performance requirement . 31
A.6 Worked example – Laboratory tests . 33
A.6.1 Bias . 33
A.6.2 Repeatability . 34
A.6.3 Influence conditions . 34
A.7 Worked example - Field tests . 35
Annex B (informative) Reference methods . 39
B.1 Laboratory methods . 39
B.2 Field (in situ) methods . 39
Annex C (informative) Reference uncertainty and error calculation . 41
Annex D (informative) Example report format . 43
Bibliography . 46
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EN 17694-1:2023 (E)
European foreword
This document (EN 17694-1:2023) has been prepared by Technical Committee CEN/TC 318
“Hydrometry”, the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by November 2023, and conflicting national standards shall
be withdrawn at the latest by November 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This standard is published in two parts:
— EN 17694-1, Hydrometry — Minimum performance requirements and test procedures for water
monitoring equipment — Devices for the determination of flow — Part 1: Open channel instrumentation
— EN 17694-2, Hydrometry — Minimum performance requirements and test procedures for water
monitoring equipment — Devices for the determination of flow — Part 2: Closed conduit
instrumentation
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
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SIST EN 17694-1:2023
EN 17694-1:2023 (E)
Introduction
This document is a product standard for open channel instrumentation for the determination of the flow
of waters in artificial channels (e.g. effluent discharges from industrial installations, wastewaters from
sewage treatment works, water irrigation channels, and water transfer channels). An open channel
instrument (OCI) is either a level sensor used in conjunction with a gauging structure or a velocity area
instrument or a velocity sensor. It is normally fixed in position and used to determine either volumetric
flow-rate and/or total volume passed. This document specifies general requirements, minimum
performance requirements, and test procedures. These specifications are derived from ISO 11655 [1]. An
OCI that is shown, by means of the tests, to conform with the general requirements and performance
requirements is considered to be fit for purpose. However, this document does not cover the installation
and on-going use of an OCI for which relevant standards exist.
The acronym “OCI” is used throughout this document except where it is necessary to be specific about
the particular type or component (e.g. sensor) of an instrument.
Measurement ranges are not specified as part of the performance requirements, though a minimum ratio
(maximum measured value: minimum measured value) is specified. It is for the manufacturer of the OCI
to decide on the measurement range over which the performance requirements are shown to be met by
the specified test procedures.
Water monitoring equipment is widely used for compliance monitoring purposes under national and
European regulations.
5
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SIST EN 17694-1:2023
EN 17694-1:2023 (E)
1 Scope
This document specifies general requirements, minimum performance requirements and test procedures
for open channel instrumentation used to determine either volumetric flow-rate and/or total volume
passed of waters in artificial open channels. It covers the following technology categories:
— Level sensors with associated electronics designed to be used with a conventional gauging structure.
(The requirements and test procedures for gauging structures, such as weirs and flumes, are
excluded. The stage discharge characteristics for many of these structures are established and
published in national and international standards).
— Water velocity sensors.
— Integrated velocity area instruments comprising level and velocity sensors that may be separate or
combined in a single assembly.
— Velocity sensors that determine the mean water velocity through a channel.
It is recognized that for some OCIs, certain tests cannot be carried out.
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.
EN ISO 772, Hydrometry - Vocabulary and symbols (ISO 772)
CEN ISO/TS 25377, Hydrometric uncertainty guidance (HUG) (ISO/TS 25377)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 772 and CEN ISO/TS 25377
and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
aspect ratio
for side mounted sensors, the ratio of the measurement range to height where the range is the horizontal
distance from the instrument and height is the vertical distance to the surface or bottom
Note 1 to entry: Aspect ratio is fully defined in ISO 15769 and applies specifically to side mounted water velocity
sensors.
3.2
combined performance requirement
combination of individual performance requirements
3.3
determinand
property that is required to be measured
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EN 17694-1:2023 (E)
3.4
open channel instrument
OCI
device which measures the flow-rate and/or totalized volume of water passing along an open channel, or
computes such quantities from measurements of one or more properties which have a relationship with
the flow-rate
Note 1 to entry: For the purposes of this document an open channel instrument is:
— a level sensor with associated electronics designed to be used with a conventional gauging structure (e.g.
weir or flume for which the stage discharge characteristics are established and published, in a national
or international standard) or a water velocity sensor;
— an integrated velocity area device comprising level and velocity sensors that may be separate or
combined in a single assembly;
— a velocity sensor that determines the mean water velocity through a channel.
3.5
flow-rate
q
volume of water passing per unit time
3.6
influence quantity
quantity, generally external to the OCI, which may affect the performance of the equipment
3.7
measurement range
range over which the OCI conforms within the performance requirements specified in this document
Note 1 to entry: For level sensors the measurement range is expressed in terms of the depth of water above a fixed
datum (stage). For integrated velocity area devices, the measurement range is expressed in terms of volumetric
flow-rate and for velocity sensors the measurement range is expressed in terms of mean water velocity.
Note 2 to entry: The measurement range is defined from a minimum non-zero value to a maximum value.
3.8
non-contact sensor
velocity or level sensor that is not in direct contact with the water
3.9
percentage error
error in measurement expressed as a percentage of the true or actual value
Note 1 to entry: In this document the true or actual value is the reference value and percentage error is calculated
using the following equation: percentage error = 100 × (measured value – reference value)/reference value.
3.10
performance requirement
one of the quantities (described by values, tolerances, range) that define an OCI’s performance
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EN 17694-1:2023 (E)
3.11
rated operating conditions
minimum to maximum values of any environmental, water or electrical parameter within which an OCI
is designed to operate without adjustment
Note 1 to entry: The performance requirements are specified in this document.
3.12
reference conditions
specified set of values (including tolerances) of influence variables, delivering representative values of
performance requirements
3.13
reference method
method to be used to obtain the determinand value to a stated uncertainty, against which the readings
from an instrument under test can be compared
3.14
repeatability
ability of an OCI to provide closely similar indications for repeated applications of the same determinand
under the same conditions of measurement
3.15
totalized volume
total volume of water which has been measured over a period of time which commenced when the
totaliser was set to zero
3.16
totalizer
indicating device showing the totalised volume
4 Symbols
For the purposes of this document the following symbols apply.
b bias
S repeatability
R
X errors due to variations in supply voltage
V
X errors due to variations in output impedance
O
X errors due to variations in fluid temperature
FT
X errors due to variations in ambient air temperature
T
X errors due to variations in relative humidity
RH
X errors due to variations in incident light
LX
XSR errors due to variations in direct solar radiation
X errors due to variations in sensor location
S
X errors due to variations in the user defined curve
U
U combined uncertainty performance requirement
C
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EN 17694-1:2023 (E)
5 Principle
This document sets general requirements, minimum performance requirements and test procedures for
an OCI that is to be used for determining the flow of water in artificial channels.
The general requirements are based on experience of users’ needs when operating an OCI in a range of
applications.
The minimum performance requirements are parameters, derived from ISO 11655, that identify the
capability of an OCI to provide reliable measurements. The requirements specify limit values in terms of
percentage of reading for measurement bias and repeatability, and for a range of environmental and
sensor operational parameters, and for a combination of all of these values. These limit values were
established originally through dialogue with OCI manufacturers, users and regulators. They have been in
use for over 20 years and have been validated through extensive testing of OCIs. An OCI that can be
demonstrated by the specified tests to conform with the performance requirements is judged to be fit for
purpose.
For the majority of applications where OCI are used, the required parameter is volumetric flow-rate. For
an integrated velocity area instrument the performance requirements are expressed as percentage of
volumetric flow. For level sensors, the performance requirements are tighter because account has to be
taken of the inherent uncertainty of the conventional gauging structure with which it is to be used. (The
requirements and test procedures for gauging structures, such as weirs and flumes, are excluded. The
stage discharge characteristics for many of these structures are established and published in national and
international standards.) ISO standards state that the uncertainty inherent in the algorithm used to
convert the measured determinand to flow of the conventional gauging structure can be in the range of
1 % to 3 %. Mean velocity instruments require an input of the channel cross sectional area, usually
derived from a level sensor, to determine volumetric flow-rate. Allowance therefore is made for the
uncertainty of the level sensor. The performance values in Table 2 have therefore been chosen such that
the root sum square of the values for the separate level and velocity sensors equal the value for the
integrated velocity area instrument for example:
22
S =√+SS
( )
Rint Rvel Rlevel
where
SRint is the repeatability of an integrated instrument;
S is the repeatability of a velocity sensor; and
Rvel
S is the repeatability for a level sensor.
Rlevel
The overall measurement reliability of an OCI is captured by bringing the individual performance
characteristics together in the form of a combined performance characteristic expressed as a
measurement uncertainty. However, the combined performance requirement for each category of OCI is
less than the sum of the specified individual performance values combined in quadrature. This allows for
some differences in performance of OCIs within a category with respect to the applicable individual
requirements.
The laboratory test procedures are designed to show whether an OCI can conform with the applicable
performance requirements under a range of environmental and sensor operational conditions.
Laboratory testing is used to determine the performance characteristics in a systematic and consistent
way in a controlled environment.
Statistical procedures are defined for evaluation of the laboratory test data to produce the individual
performance characteristic measurement uncertainties, u, and the combined performance characteristic
measurement uncertainty, U . They are based on the ISO Guide to the Expression of Uncertainty in
C
Measurement (GUM). The procedure for calculating the combined performance characteristic
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EN 17694-1:2023 (E)
measurement uncertainty involves converting the individual performance characteristic uncertainties to
standard uncertainties. This takes account of the distribution of errors. In the GUM, standard
uncertainties are combined using a root sum of squares with due account taken of the contribution of
each component through the use of sensitivity co-efficients. To determine sensitivity co-efficients, it is
necessary to know the functions by which each component contributes to overall error. In the case of OCI
testing this will rarely be known. Hence for the purposes of this document, the sensitivity co-efficients
are all taken as 1.
The combined performance characteristic, U , is expressed as an expanded uncertainty. The expanded
C
uncertainty, (U), is obtained by multiplying the standard uncertainty by a coverage factor. The coverage
factor is determined by the confidence level. This document uses a 95 % confidence with a coverage factor
assumed to be 2.
The field trial is used to demonstrate that the performance of an OCI can be maintained under operational
conditions and to determine the OCI’s up-time.
6 General requirements
6.1 Requirements for open channel instrumentation
An OCI shall have:
a) a unique designation that unambiguously identifies the OCI (e.g. model, serial number);
b) a means of protection against inadvertent or unauthorized access to the control functions (e.g.
password, physical locks, etc.);
c) an output signal and/or display scaled in metric units (the units of measurement shall be displayed
on the indicating device);
d) one or more output signals and/or a means of displaying the measured determinand and/or either
the totalized volume and/or volumetric flow-rate. If the OCI does not incorporate a local display, it
shall be possible for an authorized person to obtain the current reading by communicating with the
OCI on site using a portable device, such as a laptop, tablet or smartphone. Communication with a
portable device to display a reading shall not interrupt the measurement and shall not allow the user
to defeat access security features;
e) a means of displaying its operating status, for example, normal operation. stand-by, maintenance
mode or malfunction;
f) a return to normal operating mode from maintenance, service or programming mode if no user
interactions hav
...
SLOVENSKI STANDARD
oSIST prEN 17694-1:2021
01-september-2021
Hidrometrija - Zahteve za tehnične lastnosti in preskusni postopki za opremo za
nadzor vode - Naprave za ugotavljanje pretoka - 1. del: Instrumenti z odprtim
kanalom
Hydrometry - Performance requirements and test procedures for water monitoring
equipment - Devices for the determination of flow Part 1: Open channel instrumentation
Hydrometrie - Leistungsanforderungen und Prüfverfahren für
Wasserüberwachungsgeräte - Geräte zur Bestimmung des Durchflusses - Teil 1:
Messgeräte für offenes Gerinne
Ta slovenski standard je istoveten z: prEN 17694-1
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
17.120.20 Pretok v odprtih kanalih Flow in open channels
oSIST prEN 17694-1:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 17694-1:2021
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oSIST prEN 17694-1:2021
DRAFT
EUROPEAN STANDARD
prEN 17694-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2021
ICS 07.060; 17.120.20
English Version
Hydrometry - Performance requirements and test
procedures for water monitoring equipment - Devices for
the determination of flow Part 1: Open channel
instrumentation
Hydrometrie - Leistungsanforderungen und
Prüfverfahren für Wasserüberwachungsgeräte - Geräte
zur Bestimmung des Durchflusses - Teil 1: Messgeräte
für offenes Gerinne
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 318.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17694-1:2021 E
worldwide for CEN national Members.
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oSIST prEN 17694-1:2021
prEN 17694-1:2021 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols. 8
5 Principle . 9
6 General requirements . 10
6.1 Requirements for open channel instrumentation . 10
6.2 Requirements for associated documentation . 11
7 Performance requirements . 12
7.1 Expression of performance requirements . 12
7.2 Performance requirements . 13
7.3 Computational accuracy . 15
7.4 Data retention . 15
7.5 Environmental requirements . 15
7.6 Water temperature requirements . 15
7.7 Installation influences. 16
7.8 Field test requirements . 16
8 Testing . 16
8.1 General requirements for testing . 16
8.2 Laboratory test conditions . 16
8.3 Reporting . 18
9 Laboratory test procedures . 18
9.1 Guidance for establishing a test plan . 18
9.2 Verification by inspection . 20
9.3 Performance tests . 20
9.3.1 Loss of power for electronic OCIs . 20
9.3.2 Bias and repeatability . 20
9.3.3 Supply voltage . 21
9.3.4 Output impedance . 21
9.3.5 Water temperature . 22
9.3.6 Ambient air temperature and relative humidity . 22
9.3.7 Direct solar radiation . 23
9.3.8 Sensor location . 25
9.3.9 Incident light . 25
9.3.10 Accuracy of computation . 25
9.3.11 Effect of channel size . 26
9.3.12 Response time . 27
10 Field test procedures . 28
10.1 Objectives of field test . 28
10.2 Field test plan . 28
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10.3 Field test requirements . 28
10.4 Error under field test conditions . 28
10.5 Up-time . 29
10.6 Maintenance . 30
Annex A (normative) Evaluation of test data . 31
Annex B (informative) Reference methods . 39
Annex C (informative) . 41
(informative) Example report format . 43
Bibliography . 46
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European foreword
This document (prEN 17694-1) has been prepared by Technical Committee CEN/TC 318 “Hydrometry”,
the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
This standard is published in two parts:
— prEN 17694-1 Hydrometry - Performance requirements and test procedures for water monitoring
equipment – Devices for the determination of flow - Part 1 Open channel instrumentation
— prEN XXXX-2 Hydrometry - Performance requirements and test procedures for water monitoring
equipment – Devices for the determination of flow - Part 2 Closed conduit instrumentation
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Introduction
This document is a product standard for open channel instrumentation for the determination of the flow
of waters in artificial channels (e.g. effluent discharges from industrial installations, wastewaters from
sewage treatment works, water irrigation channels, and water transfer channels). An open channel
instrument (OCI) is either a level sensor used in conjunction with a gauging structure or a velocity area
device or a velocity sensor. It is normally fixed in position and used to determine either volumetric flow-
rate and/or total volume passed. This document specifies general requirements, minimum performance
requirements, and test procedures. These specifications are derived from ISO 11655 [1]. An OCI that is
shown, by means of the tests, to conform with the general requirements and performance requirements
is considered to be fit for purpose. However, this document does not cover the installation and on-going
use of an OCI for which relevant standards exist.
The acronym “OCI” is used throughout this document except where it is necessary to be specific about
the particular type or component (e.g. sensor) of a device.
Measurement ranges are not specified as part of the performance requirements, though a minimum ratio
(maximum measured value: minimum measured value) is specified. It is for the manufacturer of the OCI
to decide on the measurement range over which the performance requirements are shown to be met by
the specified test procedures.
Water monitoring equipment is widely used for compliance monitoring purposes under national and
European regulations.
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1 Scope
This document specifies general requirements, minimum performance requirements and test procedures
for open channel instrumentation used to determine either volumetric flow-rate and/or total volume
passed of waters in artificial open channels. It covers the following technology categories:
— Level sensors with associated electronics designed to be used with a conventional gauging structure.
(The requirements and test procedures for gauging structures, such as weirs and flumes, are
excluded. The stage discharge characteristics for many of these structures are established and
published in national and international standards).
— Fluid velocity sensors.
Integrated velocity area devices comprising level and velocity sensors that may be separate or
combined in a single assembly.
— Velocity sensors that determine the mean water velocity through a channel.
It is recognized that for some OCIs, certain tests cannot be carried out.
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.
EN ISO 772, Hydrometry – Vocabulary and symbols (ISO 772)
CEN ISO /TS 25377, Hydrometric uncertainty guidance (HUG) (ISO/TS 25377)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 772 and CEN ISO/TS 25377
and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
aspect ratio
for side mounted sensors, the ratio of the measurement range to height where the range is the horizontal
distance from the instrument and height is the vertical distance to the surface or bottom
Note 1 to entry. Aspect ratio is fully defined in ISO 15769 and applies specifically to side mounted water velocity
sensors.
3.2
combined performance requirement
combination of individual performance requirements
3.3
determinand
property that is required to be measured
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3.4
open channel instrument
OCI
device which measures the flow-rate or totalized volume of fluid passing along an open channel, or
computes such quantities from measurements of one or more properties which have a relationship with
the flow-rate
Note 1 to entry. For the purposes of this document an open channel instrument is:
— a level sensor with associated electronics designed to be used with a conventional gauging structure (e.g.
weir or flume for which the stage discharge characteristics are established and published, in a national
or international standard) or a fluid velocity sensor;
— an integrated velocity area device comprising level and velocity sensors that may be separate or
combined in a single assembly;
— a velocity sensor that determines the mean water velocity through a channel.
3.5
flow-rate
q
the volume of water passing per unit time
3.6
influence quantity
any quantity, generally external to the OCI, which may affect the performance of the equipment
3.7
measurement range
range over which the OCI conforms within the performance requirements specified in this document
Note 1 to entry: For level sensors the measurement range is expressed in terms of the depth of water above a fixed
datum (stage). For integrated velocity area devices the measurement range is expressed in terms of volumetric flow-
rate and for velocity sensors the measurement range is expressed in terms of mean water velocity.
Note 2 to entry: The measurement range is defined from a minimum non-zero value to a maximum value.
3.8
non-contact sensor
velocity or level sensor that is not in direct contact with the fluid
3.9
percentage error
error in measurement expressed as a percentage of the true or actual value
Note 1 to entry: In this document the true or actual value is the reference value and percentage error is calculated
using the following equation: percentage error = 100 X (measured value – reference value)/reference value.
3.10
performance requirement
one of the quantities (described by values, tolerances, range) that define an OCI’s performance
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3.11
rated operating conditions
minimum to maximum values of any environmental, fluid or electrical parameter within which an OCI is
designed to operate without adjustment
Note 1 to entry: The performance requirements are specified in this document.
3.12
reference conditions
specified set of values (including tolerances) of influence variables, delivering representative values of
performance requirements
3.13
reference method
method to be used to obtain the determinand value to a stated uncertainty, against which the readings
from an instrument under test can be compared
3.14
repeatability
ability of an OCI to provide closely similar indications for repeated applications of the same determinand
under the same conditions of measurement
3.15
totalized volume
total volume of water which has been measured over a period of time which commenced when the
totaliser was set to zero
3.16
totalizer
indicating device showing the totalised volume
4 Symbols
For the purposes of this document the following symbols apply.
b Bias
S Repeatability
r
X Errors due to variations in supply voltage
V
X Errors due to variations in output impedance
O
X Errors due to variations in fluid temperature
FT
X Errors due to variations in ambient air temperature
T
X Errors due to variations in relative humidity
RH
X Errors due to variations in incident light
LX
XSR Errors due to variations in direct solar radiation
X Errors due to variations in sensor location
S
X Errors due to variations in the user defined curve
U
U Combined uncertainty performance requirement
C
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5 Principle
This document sets general requirements, minimum performance requirements and test procedures for
an OCI that is to be used for determining the flow of water in artificial channels.
The general requirements are based on experience of users’ needs when operating an OCI in a range of
applications.
The minimum performance requirements are parameters that identify the capability of an OCI to provide
reliable measurements. The requirements specify limit values in terms of percentage of reading for
measurement bias and repeatability, and for a range of environmental and sensor operational
parameters, and for a combination of all of these values. An OCI that can be demonstrated by the specified
tests to conform with the performance requirements is judged to be fit for purpose.
For the majority of applications where OCI are used, the required parameter is volumetric flow-rate. For
an integrated velocity area instrument the performance requirements are expressed as percentage of
volumetric flow. For level sensors, the performance requirements are tighter because account shall be
taken of the inherent uncertainty of the conventional gauging structure with which it is to be used. (The
requirements and test procedures for gauging structures, such as weirs and flumes, are excluded. The
stage discharge characteristics for many of these structures are established and published in national and
international standards.) ISO standards state that the uncertainty inherent in the algorithm used to
convert the measured determinand to flow of the conventional gauging structure can be in the range of
1 % to 3 %. Mean velocity instruments require an input of the channel cross sectional area, usually
derived from a level sensor, to determine volumetric flow-rate. Allowance therefore shall be made for the
uncertainty of the level sensor. The performance values in Table 2 have therefore been chosen such that
the root sum square of the values for the separate level and velocity sensors equal the value for the
integrated velocity area instrument for example:
2 22
S SS+
Rint Rvel Rlevel
where
S is the repeatability of an integrated instrument;,
Rint
S is the repeatability of a velocity senso;, and
Rvel
S is the repeatability for a level sensor.
Rlevel
The overall measurement reliability of an OCI is captured by bringing the individual performance
characteristics together in the form of a combined performance characteristic expressed as a
measurement uncertainty. However, the combined performance requirement for each category of OCI is
less than the sum of the specified individual performance values combined in quadrature. This allows for
some differences in performance of OCIs within a category with respect to the applicable individual
requirements.
The laboratory test procedures are designed to show whether an OCI can conform with the applicable
performance requirements under a range of environmental and sensor operational conditions.
Laboratory testing is used to determine the performance characteristics in a systematic and consistent
way in a controlled environment.
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Statistical procedures are defined for evaluation of the laboratory test data to produce the individual
performance characteristic measurement uncertainties, u, and the combined performance characteristic
measurement uncertainty, U . They are based on the ISO Guide to the Expression of Uncertainty in
C
Measurement (GUM). The procedure for calculating the combined performance characteristic
measurement uncertainty involves converting the individual performance characteristic uncertainties to
standard uncertainties. This takes account of the probable distribution of errors. In the GUM, standard
uncertainties are combined using a root sum of squares with due account taken of the contribution of
each component through the use of sensitivity co-efficients. To determine sensitivity co-efficients, it is
necessary to know the functions by which each component contributes to overall error. In the case of OCI
testing this will rarely be known. Hence for the purposes of this document, the sensitivity co-efficients
are all taken as 1.
The combined performance characteristic, U , is expressed as an expanded uncertainty. The expanded
C
uncertainty, (U), is obtained by multiplying the standard uncertainty by a coverage factor. The coverage
factor is determined by the confidence level. This document uses a 95 % confidence with a coverage factor
assumed to be 2.
The field trial is used to demonstrate that the performance of an OCI can be maintained under operational
conditions and to determine the OCI’s up-time.
6 General requirements
6.1 Requirements for open channel instrumentation
An OCI shall have:
a) an unique designation that unambiguously identifies the OCI (e.g. model, serial number);
b) a means of protection against inadvertent or unauthorized access to the control functions (e.g.
password, physical locks, etc);
c) an output signal and/or display scaled in metric units (the units of measurement shall be displayed
on the indicating device);
d) one or more output signals and/or a means of displaying the measured determinand and/or either
the totalized volume and / or volumetric flow-rate. If the OCI does not incorporate a local display, it
shall be possible for an authorized person to obtain the current reading by communicating with the
OCI on site using a portable device, such as a laptop, tablet or smartphone. Communication with a
portable device to display a reading shall not interrupt the measurement. Any software or application
required for this shall be downloadable free of charge from the manufacturer’s website;
e) a means of displaying its operating status, for example, normal operation. stand-by, maintenance
mode or malfunction;
f) an audible or visual method of indicating loss of power supply (applies only to OCIs operating from
an external power supply);
g) an audible or visual method of indicating when the power supply voltage is below its normal
operating limit (applies only to OCIs operating from a battery);
h) where required by the user, a means for using a user defined stage-discharge or velocity index rating
for computing flow from a level and/or velocity measurement sensor.
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6.2 Requirements for associated documentation
The following information shall be incorporated into the associated documentation:
a) operating instructions which cover the full functionality and measurement principle of the OCI;
b) guidance on the time period over which the OCI can operate continuously without requiring manual
adjustment or intervention;
NOTE 1 Automatic routines for cleaning, maintenance or recalibration can be used to maintain
performance within the required limits between manual interventions. It is up to the user to ensure that a
suitable regime is adopted for an individual application.
c) a statement of the types of gauging structures where applicable, for which the OCI is pre-
programmed to compute flow-rate without the input of data other than the type and dimensions of
the structure and a zero datum;
d) a statement defining minimum up and downstream straight lengths of channel of uniform section
adjacent to the sensor required to meet the performance characteristics of this document;
NOTE 2 Where these dimensions are specified in other standards include an appropriate reference.
e) a statement of any limitations on the channel dimensions or shape into or onto which the OCI’s sensor
can be installed; to meet the performance requirements of this document. If multiple sensors are
required, for example in wide channels, the number and spacing of these sensors shall be stated;
f) for non-contact sensors, a statement of the minimum and maximum separation distances from the
sensor face to the water surface;
NOTE 3 The maximum separation distance will be the measurement range of the level sensor plus the
minimum separation distance.
g) a statement of the positioning required for the operation of submerged sensors (e.g. aspect ratio,
distance from channel base, minimum depth of overhead water);
h) a statement of the quality (e.g. contaminants, salinity), nature and quantity of particulate or other
material that the OCI can pass whilst maintaining its performance within the limits of this document.
If a minimum level of particulate is required for operation of the OCI, this too shall be stated;
i) a statement of any specific requirements relating to the location or shielding of components
necessary to maintain performance within the limits of this document under varying environmental
conditions;
j) a statement of the measurement resolution;
NOTE 4 The stated measurement resolution can be included in the calculation of the combined performance
requirement, see A.5.
k) a statement of the rated operating conditions for the power supply;
l) a statement, for an electronic OCI, of the rated operating conditions for the signal load impedance on
the analogue output, if present;
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