oSIST prEN 17694-1:2021

Hydrometry - 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

Hidrometrija - Zahteve za tehnične lastnosti in preskusni postopki za opremo za nadzor vode - Naprave za ugotavljanje pretoka - 1. del: Instrumenti z odprtim kanalom

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Sep-2021
• ICS: 07.060 - Geology. Meteorology. Hydrology
• ICS: 17.120.20 - Flow in open channels
• Technical Committee: IMIN - Measurement instruments
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 02-Aug-2021
• Due Date: 20-Dec-2021
• Directive: 2000/60/EC - Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (substitutes Directive Reference 01/991 - Common Position on WFD)
• Ref Project: prEN 17694-1 - Hydrometry - Performance requirements and test procedures for water monitoring equipment - Devices for the determination of flow Part 1: Open channel instrumentation

Standards Content (sample)

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
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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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
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
X Errors due to variations in supply voltage
X Errors due to variations in output impedance
X Errors due to variations in fluid temperature
X Errors due to variations in ambient air temperature
X Errors due to variations in relative humidity
X Errors due to variations in incident light
XSR Errors due to variations in direct solar radiation
X Errors due to variations in sensor location
X Errors due to variations in the user defined curve
U Combined uncertainty performance requirement
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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

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

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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