Expression of performance of electrochemical analyzers - Part 4: Dissolved oxygen in water measured by membrane-covered amperometric sensors

IEC 60746-4:2018 applies to analyzers using membrane covered amperometric sensors. It applies to analyzers suitable for use in water containing liquids, ultrapure waters, fresh or potable water, sea water or other aqueous solutions, industrial or municipal waste water from water bodies (e.g. lakes, rivers, estuaries), as well as for industrial process streams and process liquids. Whilst in principle amperometric oxygen-analyzers are applicable in gaseous phases, the expression of performance in the gas phase is outside the scope of this document. This document is applicable to analyzers specified for permanent installation in any location (indoors or outdoors) using membrane-covered amperometric sensors. This edition includes the following significant technical changes with respect to the previous edition:
a) terms and definitions have been revised to meet the requirements of ISO/IEC Directives Part 2:2016.
b) ISO 5814:2012 is cited as reference for solubility tables of dissolved oxygen in water with variable salt content at different pressure and temperature.

Expression des qualités de fonctionnement des analyseurs électrochimiques - Partie 4: Oxygène dissous dans l'eau mesuré par des capteurs ampérométriques recouverts d'une membrane

IEC 60746-4:2018 s'applique aux analyseurs qui utilisent des capteurs ampérométriques recouverts d'une membrane. Il s'applique aux analyseurs convenant à une utilisation dans les liquides aqueux, l'eau extrapure, l'eau douce ou potable, l'eau de mer ou toute autre solution aqueuse, les eaux usées industrielles ou urbaines provenant de plans d'eau (lacs, rivières, estuaires, par exemple), ainsi que les effluents industriels et les liquides de process. Bien que les analyseurs d'oxygène ampérométriques s'appliquent en principe aux phases gazeuses, l'expression de leurs qualités de fonctionnement dans la phase gazeuse ne relève pas du domaine d'application du présent document. Le présent document s'applique aux analyseurs spécifiés en vue d'une installation permanente en tout lieu (en intérieur et en extérieur), qui utilisent des capteurs ampérométriques recouverts d'une membrane. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) les termes et définitions ont été révisés afin de satisfaire aux exigences des Directives ISO/IEC, Partie 2:2016.
b) la norme ISO 5814:2012 est citée en référence pour les tableaux de solubilité de l'oxygène dissous dans l'eau, avec différentes teneurs en sel à différentes pressions et temperatures.

General Information

Status
Published
Publication Date
12-Dec-2018
Current Stage
PPUB - Publication issued
Completion Date
13-Dec-2018
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IEC 60746-4
Edition 2.0 2018-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Expression of performance of electrochemical analyzers –
Part 4: Dissolved oxygen in water measured by membrane-covered
amperometric sensors
Expression des qualités de fonctionnement des analyseurs électrochimiques –
Partie 4: Oxygène dissous dans l'eau mesuré par des capteurs ampérométriques
recouverts d'une membrane
IEC 60746-4:2018-12(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60746-4
Edition 2.0 2018-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Expression of performance of electrochemical analyzers –
Part 4: Dissolved oxygen in water measured by membrane-covered
amperometric sensors
Expression des qualités de fonctionnement des analyseurs électrochimiques –
Partie 4: Oxygène dissous dans l'eau mesuré par des capteurs ampérométriques
recouverts d'une membrane
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.080; 71.040.40 ISBN 978-2-8322-6274-0

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60746-4:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

3.1 Oxygen sensor properties ....................................................................................... 7

3.2 Electronics .............................................................................................................. 7

3.3 Measurement units and solubility of oxygen ............................................................ 8

3.4 Test media .............................................................................................................. 9

4 Influence quantities for membrane covered amperometric sensors .................................. 9

4.1 Temperature ........................................................................................................... 9

4.2 Pressure ................................................................................................................. 9

4.3 Dissolved substances ............................................................................................. 9

4.4 Flow ........................................................................................................................ 9

5 Procedure for specification .............................................................................................. 9

5.1 Zero and span drift .................................................................................................. 9

5.2 Additional specifications for the sensor unit .......................................................... 10

5.2.1 Electrode and sensor materials ...................................................................... 10

5.2.2 Dimensions of the sensor .............................................................................. 10

5.2.3 Permitted temperature and pressure range .................................................... 10

5.2.4 Temperature measurement and temperature compensation ........................... 10

5.2.5 Pressure compensation ................................................................................. 10

5.2.6 Zero current ................................................................................................... 10

5.2.7 Sensor sensitivity .......................................................................................... 10

5.2.8 Stabilization time ........................................................................................... 10

5.2.9 Oxygen consumption ..................................................................................... 10

5.2.10 Flow rate ....................................................................................................... 10

5.2.11 Method and extent of sensor regeneration ..................................................... 10

6 Recommended standard values and ranges of influence quantities affecting the

performance of electronic units ...................................................................................... 10

7 Verification of values ..................................................................................................... 11

7.1 General ................................................................................................................. 11

7.1.1 General aspects of verification of values ........................................................ 11

7.1.2 Testing procedure for linearity of the electronic unit ....................................... 11

7.1.3 Rated reference conditions for testing ........................................................... 11

7.2 Simulator for testing electronic units ..................................................................... 11

7.3 Calibration solutions ............................................................................................. 11

7.4 Testing procedures for complete analyzer (sensor unit connected to

electronic unit) ...................................................................................................... 11

7.4.1 Intrinsic uncertainty ....................................................................................... 11

7.4.2 Linearity uncertainty ...................................................................................... 11

7.4.3 Repeatability ................................................................................................. 12

7.4.4 Interference uncertainty (whole analyzer) ...................................................... 12

7.4.5 Zero drift and span drift ................................................................................. 12

7.4.6 Output fluctuation of the analyzer .................................................................. 12

7.4.7 Delay times T and 90 % rise or fall times T ............................................. 13

10 90

7.4.8 Temperature compensation ........................................................................... 13

7.4.9 Operating uncertainty of the whole analyzer .................................................. 14

---------------------- Page: 4 ----------------------
IEC 60746-4:2018 © IEC 2018 – 3 –

7.4.10 Determination of the sensor unit residual signal ............................................. 14

7.4.11 Oxygen consumption ..................................................................................... 14

Annex A (informative) Supplementary general information on amperometric oxygen

sensors ................................................................................................................................. 15

A.1 Sensors' performance characteristics .................................................................... 15

A.2 Precautions ........................................................................................................... 16

A.3 Sensor calibration techniques ............................................................................... 16

Annex B (informative) Technique for the preparation of batch calibration standards by

the saturation approach [10] ................................................................................................. 18

Annex C (informative) Calibration solutions for low levels of oxygen in water

measurement ........................................................................................................................ 19

C.1 System development [10] ...................................................................................... 19

C.2 Description and operation of the system ............................................................... 19

C.3 Further developments ........................................................................................... 19

Bibliography .......................................................................................................................... 25

Figure C.1 – Laboratory rig to produce water with a low level of dissolved oxygen ................ 21

Figure C.2 – Complete system for laboratory testing dissolved oxygen monitor ..................... 22

Figure C.3 – Dimensions of block A ...................................................................................... 23

Figure C.4 – Dimensions of block B ...................................................................................... 24

---------------------- Page: 5 ----------------------
– 4 – IEC 60746-4:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPRESSION OF PERFORMANCE OF
ELECTROCHEMICAL ANALYZERS –
Part 4: Dissolved oxygen in water measured
by membrane-covered amperometric sensors
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

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with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60746-4 has been prepared by subcommittee 65B: Measurement

and control devices, of IEC technical committee 65: Industrial-process measurement, control

and automation.

This second edition cancels and replaces the first edition published in 1992. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) terms and definitions have been revised to meet the requirements of ISO/IEC Directives

Part 2:2016.

b) ISO 5814:2012 is cited as reference for solubility tables of dissolved oxygen in water with

variable salt content at different pressure and temperature.
---------------------- Page: 6 ----------------------
IEC 60746-4:2018 © IEC 2018 – 5 –
The text of this International Standard is based on the following documents:
FDIS Report on voting
65B/1128/FDIS 65B/1138/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60746 series, published under the general title Expression of

performance of electrochemical analyzers, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 7 ----------------------
– 6 – IEC 60746-4:2018 © IEC 2018
EXPRESSION OF PERFORMANCE OF
ELECTROCHEMICAL ANALYZERS –
Part 4: Dissolved oxygen in water measured
by membrane-covered amperometric sensors
1 Scope
This part of IEC 60746 is intended:

• to specify terminology, definitions and requirements for statements by manufacturers for

analyzers, sensor units and electronic units used for the determination of dissolved

oxygen partial pressure or concentration;

• to establish performance tests for such analyzers, sensor units and electronic units;

• to provide basic documents to support the applications of quality assurance standards

[1] .

This document applies to analyzers using membrane covered amperometric sensors. It

applies to analyzers suitable for use in water containing liquids, ultrapure waters, fresh or

potable water, sea water or other aqueous solutions, industrial or municipal waste water from

water bodies (e.g. lakes, rivers, estuaries), as well as for industrial process streams and

process liquids. Whilst in principle amperometric oxygen-analyzers are applicable in gaseous

phases, the expression of performance in the gas phase is outside the scope of this

document.

This document is applicable to analyzers specified for permanent installation in any location

(indoors or outdoors) using membrane-covered amperometric sensors.
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.

IEC 60746-1:2003, Expression of performance of electrochemical analyzers – Part 1: General

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60746-1 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
___________
Numbers in square brackets refer to the Bibliography.
---------------------- Page: 8 ----------------------
IEC 60746-4:2018 © IEC 2018 – 7 –
3.1 Oxygen sensor properties
3.1.1
membrane covered amperometric sensor

sensor with a membrane covered metal cathode, a metal or metal/metal salt anode, optional

auxilliary or reference electrodes and temperature sensors

Note 1 to entry: The electrochemical reduction of molecular oxygen occurs at the membrane-covered cathode.

The metal or metal/metal salt anode provides a well-defined, electrochemically reversible oxidation reaction within

the special filling electrolyte solution of the sensor. A gas-permeable membrane is employed to separate the

electrolyte filling solution from the test medium to avoid contamination and to achieve a stable diffusion potential.

In the case of applications in the gaseous phase the unit, volume fraction (v/v) are used.

Note 2 to entry: The cell can function as an electrochemical two-electrode cell, or as a potentiostatic three-

electrode cell, or either as a galvanic cell. Within potentiostatic three-electrode cells, a high-impedance, current-

free reference electrode is additionally implied to optimize the polarization voltage.

Note 3 to entry: Membrane-covered amperometric sensors are provided with temperature sensors located at the

active sites of the electrode cells being in thermal contact with the media to be measured.

3.1.2
sensor sensitivity

change in electrode current of the amperometric cell caused by the application of a partial

pressure of oxygen
3.1.3
zero current of sensor

current delivered by the sensor when the dissolved oxygen concentration or partial pressure

is zero
Note 1 to entry: The zero current is expressed in µA or in nA.
3.1.4
polarization

voltage to be applied to an amperometric cell during a time period to increase the stability of

the sensor
3.1.5
stabilization time

time period necessary for obtaining a stable measurement after reconnecting the sensor unit

to the electronic unit for polarization purposes (see 3.1.4)

Note 1 to entry: Regeneration of the sensor with a new membrane or an electrolyte change or installation of a

replacement sensor will require a subsequent stabilization time.
3.1.6
oxygen consumption

electrochemical reduction of molecular oxygen at the cathode of amperometric oxygen

sensors
3.2 Electronics
3.2.1
electronic unit

electronic device of an electrochemical two-electrode cell comprises a stabilized DC voltage

source and an electronic circuitry with a low impedance, direct current amplifier and optional

microprocessor circuitries

Note 1 to entry: If the electronic unit of the analyzer comprises a microprocessor device, the detected

amperometric signal will be digitised and evaluated to analyse the oxygen content.

Note 2 to entry: To quantify the amperometric signal of the oxygen reduction, software-based algorithmic routines

or data sets comprising solubility tables of oxygen in water (with consideration of temperature, pressure and

salinity) [2] and a vapour pressure table of water are used.
---------------------- Page: 9 ----------------------
– 8 – IEC 60746-4:2018 © IEC 2018
3.2.2
auxiliary electronics

electronic devices provided for potentiostatic circuitries and for temperature and pressure

transducers

Note 1 to entry: In electronic devices for three-electrode cells, additional potentiostatic circuitries are

implemented.
3.3 Measurement units and solubility of oxygen
3.3.1
partial pressure
units for the expression of the oxygen partial pressure (pO ):
millibar (mbar) or kilopascal (kPa)

Note 1 to entry: In the case of special applications, the units mm Hg (Torr) and inch Hg may be used with known

conversion ratio [2].

Note 2 to entry: In the case of applications in the gaseous phase the unit, volume fraction (v/v) are used.

Volume fraction is the quotient of the volume of a specified component and the sum of the volumes of all

components of a gas mixture before mixing, all volumes referring to the pressure and the temperature of the gas

mixture. Volume fraction will be expressed in %. The volume fraction and volume concentration take the same

value if, at the same state conditions, the sum of the component volumes before mixing and the volume of the

mixture are equal. However, because the mixing of two or more non-ideal gases at the same state conditions is

usually accompanied by a slight contraction (or, less frequently, a slight expansion), this is not generally the case.

[SOURCE: EN 50104:2010, 3.1.5]
3.3.2
concentration
units for expression of the dissolved oxygen concentration (cO ):
parts per million (ppm) = milligram kg
parts per billion (ppb) = µg kg

Note 1 to entry: The mass of the test medium means in this case the mass of the sample water, including salts or

other substances dissolved or suspended in it.

Note 2 to entry: Although ppm (parts per million) units are used in this document, it is sometimes convenient to

−3 −3

use the units of milligrams per litre (mg dm ) or of micrograms per litre (µg·dm ).

3.3.3
oxygen saturation index

unit for the expression of the dissolved oxygen in percent (%) to express the relative

saturation of the actual oxygen concentration (parts per million), as fraction of the theoretical

oxygen concentration (parts per million) of the air-saturated solution at the actual conditions

of pressure, temperature and salinity
3.3.4
oxygen solubility

maximal possible dissolved oxygen concentration of the water sample in contact and

equilibrium with air (air-saturated solution) at the actual conditions of pressure, temperature

and salinity

Note 1 to entry: The oxygen solubility in water is dependent on other dissolved organic and inorganic compounds,

dissolved electrolytes, salt-content in seawater (salinity) [2].
---------------------- Page: 10 ----------------------
IEC 60746-4:2018 © IEC 2018 – 9 –
3.4 Test media
3.4.1
test medium

stable mixture of gases (nitrogen, nitrogen + oxygen), saturated with water vapour or

humidifed reference air showing a known concentration or a known partial pressure of oxygen

used for performance tests

Note 1 to entry: The concentration (see 3.3.2) or partial pressure or volume fraction (see 3.3.1) of dissolved

oxygen and its uncertainty range shall be known.
3.4.2
calibration solution

stable mixture of humidified (saturated with water vapour) gases (nitrogen, oxygen) or

humidifed reference air exhibiting a known stable concentration or partial pressure or volume

fraction of oxygen (with tracable uncertainties) used for calibration of the analyzer

3.4.3
zero oxygen solution

solution with dissolved gas (pure nitrogen) or dissolved molecular or ionogenic compounds

(substitutes) used to eliminate the content of free oxygen or a gaseous phase (pure nitrogen)

saturated with water vapourSymbols
4 Influence quantities for membrane covered amperometric sensors
4.1 Temperature
the temperature has
In addition to the temperature dependent solubility-effect of oxygen [2],

an impact on membrane-covered amperometric sensors owing to the temperature-dependent

variation of the diffusion of oxygen molecules at the liquid interfaces of membrane-covered

sensors.
4.2 Pressure

Pressure affects the dissolved oxygen saturation value, or respectively the maximal oxygen

concentration or the oxygen partial pressure [2]. The air-pressure of the ambient media

(calibration with water-vapour saturated air) or respectively the sample pressure has to be

determined applying an appropriate pressure sensor or has to be manually entered at the

electronic unit (see 3.2.1).
4.3 Dissolved sub
...

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