Gas Analyzers - Expression of performance - Part 3: Paramagnetic oxygen analysers

IEC 61207-3:2019 is available as IEC 61207-3:2019 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition. IEC 61207-3:2019 applies to the three main methods for measuring oxygen by its paramagnetic property, which are outlined in the introduction. It considers essential ancillary units and applies to analyzers installed indoors and outdoors. Safety-critical applications can require additional requirements from system and analyzer specifications not covered in this document. This document is intended: - to specify terminology and definitions related to the functional performance of paramagnetic gas analyzers for the measurement of oxygen in a source gas; - to unify methods used in making and verifying statements on the functional performance of such analyzers; - to specify what tests are performed to determine the functional performance and how such tests are carried out; - to provide basic documents to support the application of internationally recognized quality management standards. This third edition cancels and replaces the second edition published in 2002. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) all references (normative and informative) have been updated, deleted or added to as appropriate; b) all the terms, descriptions and definitions relating to the document have been updated where appropriate; c) all references to “errors” have been replaced by “uncertainties” and appropriate updated definitions applied.

Angabe zum Betriebsverhalten von Gasanalysatoren - Teil 3: Paramagnetische Sauerstoffanalysatoren

Analyseurs de gaz - Expression des performances - Partie 3: Analyseurs d'oxygène paramagnétiques

IEC 61207-3:2019 est disponible sous forme de IEC 61207-3:2019 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente. IEC 61207-3:2019 traite des trois principales méthodes de mesure de l’oxygène par sa propriété paramagnétique présentées dans l'introduction. Elle porte sur des unités auxiliaires essentielles et concerne les analyseurs installés à l’intérieur comme à l’extérieur. Les applications présentant un risque particulier du point de vue de la sécurité peuvent nécessiter des exigences supplémentaires quant aux spécifications du système et de l'analyseur qui ne sont pas traitées dans la présente norme. La présente norme a pour objet: - de spécifier la terminologie et les définitions relatives aux performances fonctionnelles des analyseurs de gaz paramagnétiques utilisés pour le mesurage de l'oxygène dans un gaz source; - d’unifier les méthodes utilisées en fournissant et en vérifiant les indications relatives aux performances fonctionnelles de ces analyseurs; - de spécifier les essais à effectuer pour déterminer les performances fonctionnelles et la manière de réaliser ces essais; - fournir des documents de base appuyant l'application des normes de gestion de la qualité reconnues sur le plan international. Cette troisième édition annule et remplace la deuxième édition parue en 2002. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: a) toutes les références (normatives et informatives) ont été mises à jour, retirées ou ajoutées comme il convient; b) tous les termes, descriptions et définitions en rapport avec le document ont été mis à jour le cas échéant; c) toutes les références aux "erreurs" ont été remplacées par le terme «incertitudes» et les définitions ont été mises à jour comme il convient.

Analizatorji plina - Izražanje lastnosti - 3. del: Paramagnetni analizatorji kisika (IEC 61207-3:2019)

Ta dokument se uporablja za tri glavne načine merjenje kisika na podlagi njegove paramagnetnosti, ki so opisani v uvodu. Obravnava osnovne pomožne enote in se uporablja za analizatorje, ki so postavljeni v notranjih prostorih ali na prostem. Pri načinih uporabe, pri katerih je ključna varnost, so lahko zahtevane dodatne zahteve glede specifikacij sistema in analizatorja, ki niso zajete v tem dokumentu. Namen tega dokumenta je: – določiti terminologijo in definicije v zvezi s funkcionalnimi lastnostmi paramagnetnih analizatorjev plina za merjenje kisika v izhodnem plinu; – poenotiti metode, ki se uporabljajo pri ustvarjanju in preverjanju navedb o funkcionalnih lastnostih takšnih analizatorjev; – določiti, katere preskuse je treba opraviti, da se določijo funkcionalne lastnosti, in kako jih je treba opraviti; – zagotoviti osnovne dokumente za podporo uporabe mednarodno priznanih standardov vodenja kakovosti.

General Information

Status
Published
Publication Date
22-Aug-2019
Technical Committee
Drafting Committee
Current Stage
6060 - Document made available
Due Date
11-Jun-2018

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SLOVENSKI STANDARD
SIST EN IEC 61207-3:2019
01-november-2019
Nadomešča:
SIST EN 61207-3:2002

Analizatorji plina - Izražanje lastnosti - 3. del: Paramagnetni analizatorji kisika (IEC

61207-3:2019)

Gas Analyzers - Expression of performance - Part 3: Paramagnetic oxygen analysers

(IEC 61207-3:2019)
Angabe zum Betriebsverhalten von Gasanalysatoren - Teil 3: Paramagnetische
Sauerstoffanalysatoren (IEC 61207-3:2019)
Analyseurs de gaz - Expression des performances - Partie 3: Analyseurs d'oxygène
paramagnétiques (IEC 61207-3:2019)
Ta slovenski standard je istoveten z: EN IEC 61207-3:2019
ICS:
71.040.40 Kemijska analiza Chemical analysis
SIST EN IEC 61207-3:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 61207-3:2019
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SIST EN IEC 61207-3:2019
EUROPEAN STANDARD EN IEC 61207-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2019
ICS 19.040; 71.040.40 Supersedes EN 61207-3:2002 and all of its amendments
and corrigenda (if any)
English Version
Gas Analyzers - Expression of performance - Part 3:
Paramagnetic oxygen analysers
(IEC 61207-3:2019)

Analyseurs de gaz - Expression des performances - Partie Angabe zum Betriebsverhalten von Gasanalysatoren - Teil

3: Analyseurs d'oxygène paramagnétiques 3: Paramagnetische Sauerstoffanalysatoren

(IEC 61207-3:2019) (IEC 61207-3:2019)

This European Standard was approved by CENELEC on 2019-07-31. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 61207-3:2019 E
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SIST EN IEC 61207-3:2019
EN IEC 61207-3:2019 (E)
European foreword

The text of document 65B/1155/FDIS, future edition 3 of IEC 61207-3, prepared by SC 65B

"Measurement and control devices" of IEC/TC 65 "Industrial-process measurement, control and

automation" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as

EN IEC 61207-3:2019.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2020-04-30

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2022-07-31

document have to be withdrawn

This document supersedes EN 61207-3:2002 and all of its amendments and corrigenda (if any).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

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

Endorsement notice

The text of the International Standard IEC 61207-3:2019 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards

indicated:
IEC 61115 NOTE Harmonized as EN 61115
IEC 60654-1 NOTE Harmonized as EN 60654-1
ISO 9001 NOTE Harmonized as EN ISO 9001
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SIST EN IEC 61207-3:2019
EN IEC 61207-3:2019 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61207-1 - Expression of performance of gas EN 61207-1 -
analyzers - Part 1: General
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SIST EN IEC 61207-3:2019
IEC 61207-3
Edition 3.0 2019-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Gas analyzers – Expression of performance –
Part 3: Paramagnetic oxygen analyzers
Analyseurs de gaz – Expression des performances –
Partie 3: Analyseurs d'oxygène paramagnétiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040; 71.040.40 ISBN 978-2-8322-7046-2

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
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CONTENTS

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

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 Procedures for specification .......................................................................................... 15

4.1 General ................................................................................................................. 15

4.2 Specification of essential ancillary units and services ........................................... 15

4.2.1 Sampling system ........................................................................................... 15

4.2.2 Services ........................................................................................................ 15

4.3 Additional characteristics related to specification of performance .......................... 16

4.4 Important aspects related to specification of performance ..................................... 16

4.4.1 General ......................................................................................................... 16

4.4.2 Rated range of ambient temperature .............................................................. 16

4.4.3 Rated range of sample gas temperature ........................................................ 16

4.4.4 Rated range of ambient pressure ................................................................... 17

4.4.5 Rated range of sample pressure .................................................................... 17

4.4.6 Rated range of sample flow ........................................................................... 17

4.4.7 Rated range of sample dew point ................................................................... 17

4.4.8 Rated range of sample particulate content ..................................................... 17

4.4.9 Rated range of interference uncertainties ...................................................... 18

4.4.10 Rated range of linearity uncertainty ............................................................... 18

4.4.11 Rated ranges of influence quantities .............................................................. 18

5 Procedures for compliance testing ................................................................................. 18

5.1 Analyzer testing .................................................................................................... 18

5.1.1 General ......................................................................................................... 18

5.1.2 Test equipment .............................................................................................. 18

5.2 Testing procedures ............................................................................................... 19

5.2.1 General ......................................................................................................... 19

5.2.2 Interference uncertainty ................................................................................. 19

5.2.3 Wet samples .................................................................................................. 20

5.2.4 Delay times, rise time, fall time ...................................................................... 20

Annex A (informative) Interfering gases ............................................................................... 22

Annex B (informative) Methods of preparation of water vapour in test gases ........................ 26

Bibliography .......................................................................................................................... 28

Figure 1 – Magnetic auto-balance system with current feedback ............................................. 9

Figure 2 – Thermomagnetic oxygen sensor ........................................................................... 11

Figure 3 – Differential pressure oxygen sensor ..................................................................... 12

Figure 4 – Typical sampling systems – Filtered and dried system with pump for wet

samples ................................................................................................................................ 13

Figure 5 – Typical sampling system – Steam-aspirated system with water wash for wet

samples ................................................................................................................................ 14

Figure 6 – General test arrangement – Dry gases ................................................................. 19

Figure 7 – Test apparatus to apply gases and water vapour to analysis systems .................. 21

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Table A.1 – Zero correction factors for current gases ............................................................ 23

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GAS ANALYZERS –
EXPRESSION OF PERFORMANCE –
Part 3: Paramagnetic oxygen analyzers
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

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

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-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

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

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

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

misinterpretation by any end user.

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

transparently to the maximum extent possible in their national and regional publications. Any divergence

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

the latter.

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

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

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 61207-3 has been prepared by sub-committee 65B: Measurement

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

and automation.

This third edition cancels and replaces the second edition published in 2002. This edition

constitutes a technical revision.

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

edition:

a) all references (normative and informative) have been updated, deleted or added to as

appropriate;

b) all the terms, descriptions and definitions relating to the document have been updated

where appropriate;
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SIST EN IEC 61207-3:2019
IEC 61207-3:2019 © IEC 2019 – 5 –

c) all references to “errors” have been replaced by “uncertainties” and appropriate updated

definitions applied.
The text of this International Standard is based on the following documents:
FDIS Report on voting
65B/1155/FDIS 65B/1157/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.

This International Standard is to be used in conjunction with IEC 61207-1:2010.

A list of all parts in the IEC 61207 series, published under the general title Gas analyzers –

Expression of performance, 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.
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INTRODUCTION

Paramagnetic oxygen analyzers respond to the partial pressure of oxygen in the measured

gas, and the volumetric concentration is then determined by knowledge of the total pressure,

as in many other gas analyzers. Due to this fact, many paramagnetic oxygen analyzers use

pressure compensation (see 4.4.4 and 4.4.5). They are used in a wide range of industrial,

laboratory, medical, and other applications where the rated measuring range of the analyzer

is between 0 % to 1 % and 0 % to 100 %, at reference pressure (usually near atmospheric).

Only a few gases display significant paramagnetism (for example, oxygen, nitric oxide and

nitrogen dioxide), and oxygen has the strongest paramagnetic susceptibility (see Annex A)

among gases. By employing this particular property of oxygen, analyzers have been designed

that can be highly specific to the measurement in most industrial and medical applications,

where, for example, high background levels of hydrocarbons or moisture may be present.

There are several different techniques described for measuring oxygen by its paramagnetic

property, but three main methods have evolved over many years of commercial application.

The three methods are:
– automatic null balance;
– thermomagnetic or magnetic wind;
– differential pressure or Quincke.

These methods all require the sample gas to be clean and non-condensing, though some

versions work at elevated temperatures so that samples that are likely to condense at a lower

temperature can be analyzed. Because of this requirement, analyzers often require a sample

system to condition the sample prior to measurement.
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IEC 61207-3:2019 © IEC 2019 – 7 –
GAS ANALYZERS –
EXPRESSION OF PERFORMANCE –
Part 3: Paramagnetic oxygen analyzers
1 Scope

This part of IEC 61207 applies to the three main methods for measuring oxygen by its

paramagnetic property, which are outlined in the introduction. It considers essential ancillary

units and applies to analyzers installed indoors and outdoors.

Safety-critical applications can require additional requirements from system and analyzer

specifications not covered in this document.
This document is intended

– to specify terminology and definitions related to the functional performance of para-

magnetic gas analyzers for the measurement of oxygen in a source gas;

– to unify methods used in making and verifying statements on the functional performance of

such analyzers;

– to specify what tests are performed to determine the functional performance and how such

tests are carried out;

– to provide basic documents to support the application of internationally recognized quality

management standards.
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 61207-1, Expression of performance of gas analyzers – Part 1: General
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

NOTE Although cgs (centimetre-gram-second) units have been used in this document, SI (Système International)

units (such as defined in IUPAC [1] ) can also be used.

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
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3.1
magnetic susceptibility

measure (X) of the variation of the intensity of a magnetic field H, existing in a vacuum, when

the vacuum is substituted (filled) by the test substance, expressed as:
H −H
where
H is the magnetic field intensity in vacuum
H is the magnetic field intensity in the test substance

Note 1 to entry: H – H is also known as the magnetisation MV (magnetic dipole per unit volume) and therefore

this is also the volume magnetic susceptibility.
3.2
paramagnetism

property of substances causing an increase of the magnetic field intensity (X > 0)

3.3
diamagnetism
property of substances causing a diminution of the magnetic field intensity
(X < 0 because H < H)
3.4
specific magnetic susceptibility
ratio of magnetic susceptibility to the density derived as follows:
X =
where

D is the density of the considered substance, expressed in g·cm at 273,15 K, 101,3 kPa

3 −1

Note 1 to entry: The measuring unit of X is therefore cm ·g . This is also known as the mass magnetic

susceptibility.
3.5
molar magnetic susceptibility

specific magnetic susceptibility multiplied by the molecular mass (M) of the substance

considered:
X X⋅M
where
M is expressed in g per mole (g·mol ) (for oxygen M = 31,998 8)
3 −1
Note 1 to entry: The measuring unit of X is therefore cm ·mol .

Note 2 to entry: Electrons determine the magnetic properties of matter in two ways:

– an electron can be considered as a small sphere of negative charge spinning on its axis. This spinning charge

produces a magnetic moment;

– an electron travelling in an orbit around a nucleus will also produce a magnetic moment.

It is the combination of the spin moment and the orbital moment that governs the resulting magnetic properties of

an individual atom or ion.
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In paramagnetic materials, the main contribution to the magnetic moment comes from unpaired electrons. It is the

configuration of the orbital electrons and their spin orientations that establish the paramagnetism of the oxygen

molecule and distinguish it from most other gases.

Note 3 to entry: When paramagnetic gases are placed within an external magnetic field, the flux within the gas is

higher than it would be in a vacuum, thus paramagnetic gases are attracted to the part of the magnetic field with

the strongest magnetic flux. On the contrary, diamagnetic substances contain magnetic dipoles which cancel out

some lines of force from the external field; thus diamagnetic gases are subject to repulsion by the magnetic flux.

Note 4 to entry: The molar magnetic susceptibility of oxygen is inversely proportional to the absolute temperature.

According to Van Vleck [2] the molar susceptibility of oxygen can be approximated by Equation (4).

8L⋅µ
For oxygen, X = (4)
3kT
where
3 −1
X is the molar susceptibility of oxygen, expressed in cm ·mol ;
23 −1
L is the Avogadro constant = 6,022 7 × 10 mol ;
−24 2
µ is the Bohr magneton = 9,274 × 10 A·m ;
−23 −1
k is the Boltzmann constant = 1,38 × 10 J·K ;
T is the temperature, expressed in K (kelvin).
Equation (4) can be written as follows:
1010557
−6 3 −1
X = × 10 cm ·mol (only for oxygen).

Note 5 to entry: A full understanding of paramagnetism and diamagnetism can be obtained from physics and

inorganic chemistry textbooks. The explanation in this document is to give the user of paramagnetic oxygen

analyzers a simple understanding of the physical property utilized.
3.6
automatic null balance analyzer

analyzer that uses, as a general principle of operation, the displacement of a body containing

a vacuum or a diamagnetic gas, from a region of high magnetic field by paramagnetic oxygen

molecules
Note 1 to entry: See Figure 1.
Figure 1 – Magnetic auto-balance system with current feedback

Note 2 to entry: The measuring cell typically employs a glass dumb-bell, with the spheres containing nitrogen,

suspended on a torsion strip between magnetic pole pieces or magnets that produce a very strong magnetic field

gradient around the dumb-bell. The dumb-bell is then deflected when oxygen molecules enter the measuring cell, a

force being exerted on the dumb-bell by the oxygen molecules which are attracted to the strongest part of the

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magnetic field. By use of an optical lever, a magnetic actuation coil, and suitable electronics to generate a

feedback signal that nulls the magnetic susceptibility force, an output that is directly proportional to the partial

pressure of oxygen can be achieved. The transducer can be maintained at a constant temperature to prevent the

variations in magnetic susceptibility to temperature from introducing uncertainties. Alternatively, built-in

temperature sensors may be used to provide temperature compensation of the oxygen reading. Additionally, the

elevated temperature helps in applications where the sample is not particularly dry. Some analyzers are designed

so that the transducer operates at a temperature in excess of 373,15 K (100 °C) to further facilitate applications

where condensates would form at a lower temperature. Paramagnetic sensor orientation may also affect the

oxygen measurement uncertainty and this may be corrected by using a compensation algorithm using, for example,

a three-dimensional accelerometer to determine the sensor orientation relative to its orientation during calibration.

Due to the mechanical nature of this type of device, there is some inherent susceptibility to vibrational and

gyroscopic motion, potentially resulting in increased measurement uncertainty.
3.7
thermomagnetic analyzer
3.7.1
magnetic wind analyzer

analyzer that uses the temperature dependence of the magnetic susceptibility to generate a

magnetically induced gas flow which can then be measured by a flow sensor

Note 1 to entry: The sample gas passes into a chamber designed in such a way that the inlet splits the flow.

Note 2 to entry: See Figure 2.
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Figure 2 – Thermomagnetic oxygen sensor

Note 3 to entry: The two flows recombine at the outlet. A connecting tube is placed centrally with the flow sensor

wound on it. Half of the connecting tube is placed between the poles of a strong magnet. The flow sensor is

effectively two coils of wire heated to about 353,15 K (80 °C) by passage of a current. The cold oxygen molecules

are diverted by the magnetic field into the central tube, and, as they heat up, their magnetic susceptibility is

reduced and more cold oxygen molecules enter the connecting tube. A flow of oxygen is generated in this way

through the transversal connecting tube, with the effect of cooling the first coil (which is placed in the magnetic

field area), while the temperature of the second coil is not essentially influenced by this transversal flow. Since the

two coils are wound with thermosensitive wire (for example, platinum wire) and connected together to build a

Wheatstone bridge, the resulting unbalance current is a nearly proportional function of the oxygen partial pressure

in the test gas.

More recent analyzers use more refined measuring cells, toroidal shaped resistors instead of the two-coil flow

sensor, and employ temperature control to minimize ambient temperature changes.

As this method relies on heat transfer, the thermal conductivity of background gases will affect the oxygen reading

and the composition of the background has to be known. Some analyzers can give a first-order correction for this

by utilizing further compensation devices.

Thermomagnetic analyzers do not produce a strictly linear output and additional signal processing is required to

linearize the output.
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3.8
Quincke analyzer
3.8.1
differential pressure analyzer

analyzer that uses a pneumatic balance system established by using a flowing reference gas

(such as nitrogen or air)

Note 1 to entry: The measuring cell is designed so that at the reference gas inlet the flow is divided into two

paths. These flows recombine at the reference gas outlet, where the sample is also introduced. A differential

pressure sensor (or microflow sensor) is positioned across the two reference gas flows so that any imba

...

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