SIST EN ISO 6145-4:2008

Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 4: Continuous syringe injection method (ISO 6145-4:2004)

This part of ISO 6145 specifies a method for continuous production of calibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by continuous injection of the calibration component(s) into a complementary gas stream by means of a syringe. If pre-mixed gases are used instead of pure gases (see Annex A), much lower volume fractions can be obtained. The volume flow rates, from which the volume fractions are determined, can be calculated from the individual flow rates and can be independently measured by a suitable method given in ISO 6145-1. The merits of the method are that a substantial quantity of the gas mixture can be prepared on a continuous basis and that multi-component mixtures can be prepared almost as readily as binary mixtures if the appropriate number of syringes is utilized, or if the syringe already contains a multi-component mixture of known composition. This method also provides a convenient means for increasing the volume fraction of the calibration component in the mixture in small steps. It is therefore a useful method for evaluation of other characteristics of gas analysers, such as minimum detection limit and dead zone, as well as accuracy. The relative expanded uncertainty in the volume fraction obtainable for a binary mixture (at a coverage factor of 2) is 5 % and the range of applicability is 10-5 to 10-2.

Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 4: Kontinuierliches Spritzen-Injektionsverfahren (ISO 6145-4:2004)

DDieser Teil der ISO 6145 legt ein Verfahren zur kontinuierlichen Herstellung von Kalibriergasgemischen mit zwei oder mehr Komponenten aus reinen Gasen oder anderen Gasgemischen durch kontinuierliche Injektion der Kalibrierkomponente(n) in einen Grundgasstrom mittels einer Spritze fest.
Wenn Vorgemische an Stelle von reinen Gasen verwendet werden (siehe Anhang A), so lassen sich viel niedrigere Volumenanteile erreichen. Die Volumenströme, aus denen die Volumenanteile bestimmt werden, können aus den einzelnen Durchflussgeschwindigkeiten berechnet werden, und sie können mit einem geeigneten Verfahren aus ISO 6145-1 unabhängig gemessen werden.
Die Vorteile des Verfahrens bestehen darin, dass eine substantielle Menge des Gasgemischs auf kontinuierlicher Basis hergestellt werden kann, und dass sich Multikomponenten-Gemische bei Verwendung einer entsprechenden Zahl von Spritzen oder, wenn die Spritze bereits ein Multikomponenten-Gemisch bekannter Zusammensetzung enthält, fast ebenso leicht herstellen lassen wie binäre Gemische. Dieses Verfahren stellt auch ein zweckdienliches Hilfsmittel dar, um den Volumenanteil der Kalibrierkomponente in dem Gemisch in kleinen Schritten zu erhöhen. Es ist daher ein nützliches Verfahren für die Ermittlung anderer Kenngrößen von Gasanalysatoren wie der unteren Nachweisgrenze und der Totzone sowie der Genauigkeit. Die relative erweiterte Unsicherheit des Volumenanteils, die sich bei einem binären Gemisch erreichen lässt, beträgt 5 % (bei einem Überdeckungsfaktor von 2), und der Anwendungsbereich ist 10–5 bis 10–2.

Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de méthodes volumétriques dynamiques - Partie 4: Méthode continue par seringue d'injection (ISO 6145-4:2004)

L'ISO 6145‑4:2004 décrit une méthode de production continue de mélanges de gaz pour étalonnage, contenant au moins deux constituants, à partir de gaz purs ou d'autres mélanges de gaz, par injection continue des constituants étalons dans un gaz de complément à l'aide d'une seringue.
Si des prémélanges de gaz sont utilisés à la place de gaz purs, des fractions volumiques plus petites peuvent être obtenues. Les débits volumiques, à partir desquels les fractions volumiques sont déterminées, peuvent être calculés à partir des débits individuels et mesurés de manière indépendante selon une méthode appropriée donnée dans l'ISO 6145-1.
La méthode a pour mérite de permettre la préparation d'une quantité significative de mélange de gaz en continu, et la préparation de mélanges à constituants multiples presque aussi aisément que les mélanges à base de deux constituants si un nombre approprié de seringues est utilisé ou si la seringue contient déjà un mélange à constituants multiples de composition connue. Cette méthode présente également un moyen pratique d'augmenter, étapes par étapes, la fraction volumique du constituant étalon dans le mélange. Il s'agit donc d'une méthode utile d'évaluation des autres caractéristiques des analyseurs de gaz, telles que la limite de détection minimale et la zone morte, ainsi que l'exactitude. L'incertitude relative élargie dans la fraction volumique qu'il est possible d'obtenir pour un mélange à base de deux constituants (selon un facteur d'élargissement de 2) est de 5 % et la plage d'applicabilité de 10-5 à 10-2.

Analiza plinov - Priprava kalibracijske plinske zmesi z uporabo dinamičnih volumetričnih metod. - 4. del: Metoda s kontinuiranim injekcijskim vbrizgavanjem (ISO 6145-4:2004)

General Information

• Status: Published
• Publication Date: 04-Sep-2008
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: NAD - Petroleum products, lubricants and related products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 29-Aug-2008
• Due Date: 03-Nov-2008
• Completion Date: 05-Sep-2008
• Ref Project: EN ISO 6145-4:2008 - Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 4: Continuous syringe injection method (ISO 6145-4:2004)

Relations

• Replaces: SIST ISO 6145-4:1995 - Gas analysis -- Preparation of calibration gas mixtures -- Dynamic volumetric methods -- Part 4: Continuous injection method
• Effective Date: 01-Oct-2008

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 6145-4:2008
01-oktober-2008
$QDOL]DSOLQRY3ULSUDYDNDOLEUDFLMVNHSOLQVNH]PHVL]XSRUDERGLQDPLþQLK
YROXPHWULþQLKPHWRGGHO0HWRGDVNRQWLQXLUDQLPLQMHNFLMVNLPYEUL]JDYDQMHP
,62
Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods
- Part 4: Continuous syringe injection method (ISO 6145-4:2004)
Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-
volumetrischen Verfahren - Teil 4: Kontinuierliches Spritzen-Injektionsverfahren (ISO
6145-4:2004)
Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de
méthodes volumétriques dynamiques - Partie 4: Méthode continue par seringue
d'injection (ISO 6145-4:2004)
Ta slovenski standard je istoveten z: EN ISO 6145-4:2008
ICS:
71.040.40 Kemijska analiza Chemical analysis
SIST EN ISO 6145-4:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6145-4:2008

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SIST EN ISO 6145-4:2008
EUROPEAN STANDARD
EN ISO 6145-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2008
ICS 71.040.40

English Version
Gas analysis - Preparation of calibration gas mixtures using
dynamic volumetric methods - Part 4: Continuous syringe
injection method (ISO 6145-4:2004)
Analyse des gaz - Préparation des mélanges de gaz pour Gasanalyse - Herstellung von Kalibriergasgemischen mit
étalonnage à l'aide de méthodes volumétriques Hilfe von dynamisch-volumetrischen Verfahren - Teil 4:
dynamiques - Partie 4: Méthode continue par seringue Kontinuierliches Spritzen-Injektionsverfahren (ISO 6145-
d'injection (ISO 6145-4:2004) 4:2004)
This European Standard was approved by CEN on 30 July 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6145-4:2008: E
worldwide for CEN national Members.

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SIST EN ISO 6145-4:2008
EN ISO 6145-4:2008 (E)
Contents Page
Foreword.3

2

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SIST EN ISO 6145-4:2008
EN ISO 6145-4:2008 (E)
Foreword
The text of ISO 6145-4:2004 has been prepared by Technical Committee ISO/TC 158 “Analysis of gases” of
the International Organization for Standardization (ISO) and has been taken over as EN ISO 6145-4:2008 by
Technical Committee CEN/SS N21 “Gaseous fuels and combustible gas” the secretariat of which is held by
CMC.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by February 2009, and conflicting national standards shall be withdrawn
at the latest by February 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 6145-4:2004 has been approved by CEN as a EN ISO 6145-4:2008 without any modification.

3

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SIST EN ISO 6145-4:2008

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SIST EN ISO 6145-4:2008
INTERNATIONAL ISO
STANDARD 6145-4
Second edition
2004-06-15
Gas analysis — Preparation of calibration
gas mixtures using dynamic volumetric
methods —
Part 4:
Continuous syringe injection method
Analyse des gaz — Préparation des mélanges de gaz pour étalonnage à
l'aide de méthodes volumétriques dynamiques —
Partie 4: Méthode continue par seringue d'injection

Reference number
ISO 6145-4:2004(E)
©
ISO 2004

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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
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Published in Switzerland
©
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Application to preparation of gas mixtures . 2
4.1 Description of the experimental procedure . 2
4.2 Area of validity . 3
4.3 Operating conditions . 4
5 Expression of results . 4
5.1 Volume fraction . 4
5.2 Sources of uncertainty . 4
5.3 Uncertainty of volume fraction . 5
Annex A (informative) Pre-mixed gases for preparation of mixtures of high dilution . 6
Annex B (informative) Example of apparatus for preparation of calibration gas mixtures . 7
Annex C (informative) Practical hints . 9
Annex D (informative) Example of the determination of the uncertainty in the concentration of a
calibration gas mixture prepared by the continuous injection method . 12
Bibliography . 15
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 6145-4 was prepared by Technical Committee ISO/TC 158, Analysis of gases.
This second edition cancels and replaces the first edition (ISO 6145-4:1986), which has been technically
revised.
ISO 6145 consists of the following parts, under the general title Gas analysis — Preparation of calibration gas
mixtures using dynamic volumetric methods:
— Part 1: Methods of calibration
— Part 2: Volumetric pumps
— Part 4: Continuous syringe injection method
— Part 5: Capillary calibration devices
— Part 6: Critical orifices
— Part 7: Thermal mass-flow controllers
— Part 8: Diffusion method
— Part 9: Saturation method
— Part 10: Permeation method
— Part 11: Electrochemical generation
ISO 6145-3, entitled Periodic injections into a flowing gas, has been withdrawn.
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
Introduction
This part of ISO 6145 is one of a series of standards dealing with various dynamic volumetric methods used for
the preparation of calibration gas mixtures.
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SIST EN ISO 6145-4:2008
.
vi

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SIST EN ISO 6145-4:2008
INTERNATIONAL STANDARD ISO 6145-4:2004(E)
Gas analysis — Preparation of calibration gas mixtures using
dynamic volumetric methods —
Part 4:
Continuous syringe injection method
1Scope
This part of ISO 6145 specifies a method for continuous production of calibration gas mixtures, containing two
or more components, from pure gases or other gas mixtures by continuous injection of the calibration
component(s) into a complementary gas stream by means of a syringe.
If pre-mixed gases are used instead of pure gases (see Annex A), much lower volume fractions can be
obtained. The volume flow rates, from which the volume fractions are determined, can be calculated from the
individual flow rates and can be independently measured by a suitable method given in ISO 6145-1.
The merits of the method are that a substantial quantity of the gas mixture can be prepared on a continuous
basis and that multi-component mixtures can be prepared almost as readily as binary mixtures if the
appropriate number of syringes is utilized, or if the syringe already contains a multi-component mixture of
known composition. This method also provides a convenient means for increasing the volume fraction of the
calibration component in the mixture in small steps. It is therefore a useful method for evaluation of other
characteristics of gas analysers, such as minimum detection limit and dead zone, as well as accuracy. The
relative expanded uncertainty in the volume fraction obtainable for a binary mixture (at a coverage factor of 2) is
−5 −2
and the range of applicability is to .
5% 10 10
2 Normative references
The following referenced documents are indispensable for the application 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.
ISO 6143, Gas analysis — Comparison methods for determining and checking the composition of calibration
gas mixtures
ISO 6145-1, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods —
Part 1: Methods of calibration
3 Principle
The calibration component, either in the gaseous or liquid phase, is displaced from a syringe, through a
capillary which may be the needle of the syringe, the plunger of which is continuously driven by a suitable
variable-speed motor, into a complementary gas stream.
The volume fraction, ϕ of calibration component, AB, in a mixture with complementary gas, , is given by
A
Equation (1):
ϕ =q /(q +q ) (1)
A A A B
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
where
q is the volume flow rate of the calibration component, A;
A
q is the volume flow rate of the complementary gas, B.
B
If the calibration component is injected in the liquid phase, the flow rate in the gaseous phase on evaporation is
given by Equation (2):
(2)
q =(q ×ρ ) /ρ
A A,l A,l A,g
where
q is the volume flow rate of the injected liquid, in the same units as q ;
A,l A
ρ is the density of the liquid component at the temperature at which the mixture is prepared;
A,l
ρ is the density of the component in the gaseous phase, expressed in the same units and at the same
A,g
temperature as ρ .
A,l
Substitution of Equation (2) in Equation (1) then provides the value of ϕ in terms of the parameters listed
A
above.
4 Application to preparation of gas mixtures
4.1 Description of the experimental procedure
4.1.1 Apparatus
Schematic diagrams of examples of apparatus for preparation of binary mixtures are shown in Annex B;
Figure B.1 presents the apparatus for filling a syringe with a gaseous calibration component and Figure B.2
shows a mixing system for preparation of the calibration gas mixture.
4.1.2 Selection and calibration of syringe for the calibration component
The flow rate of the calibration component is determined by parallel selection of the cross-sectional area of the
syringe barrel and the linear velocity of the plunger. Sometimes, for preparation of a mixture of given volume
fraction of the calibration component, it may be preferable to use a syringe of larger cross-section (larger
capacity) in combination with a lower plunger velocity, and in other cases a smaller cross-section with higher
plunger velocity may provide the better combination (refer for practical hints to Annex C).
Select a suitable combination of linear speed of the syringe drive mechanism and metering syringe of volume
appropriate to the volume fraction, and the uncertainty in that volume fraction, of the calibration gas mixture to
be prepared.
In order to validate the uniformity of the syringe barrel, since this is a dynamic method, determine the volume of
the gas or liquid delivered by the syringe at several graduation marks, and at the temperature at which the gas
mixture is prepared. It is necessary, therefore, to allow time for the syringe to return to ambient temperature
after it has been warmed, for example by handling, before any measurements are made at any stage. This
volume calibration shall be derived from traceable mass measurements of a suitable liquid of known density in
the syringe. Since the calibration is to be carried out at several points, i.e. with the syringe partially filled,
precautions shall be taken to ensure that the meniscus of the liquid is horizontal when observations of its
position are made.
An example of the methodology is presented in Annex C.
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
4.1.3 Calibration of the syringe driver
Calibrate the syringe driver at the temperature at which the gas mixture is prepared, and against reference
equipment which is traceable to international length and time standards. A recommended method for calibration
against a digital micrometer and a digital timer is also presented in Annex C.
4.1.4 Preparation of the calibration gas mixture
When the calibration component is in the gaseous phase apparatus, an example of which is shown in
Figure B.1, for evacuating, purging and filling the reservoir and filling the syringe shall be used. The procedure
is then as follows.
a) Close the shut-off valve on the cylinder of calibration component.
b) Evacuate the entire apparatus until the pressure has been reduced to a value which is sufficiently low, such
that any residual gas in the reservoir makes no significant contribution to the volume fraction and has no
effect on the stability of the final calibration gas mixture.
−3
A residual pressure of approximately 100 Pa (1× 10 bar) has been found to be suitable. However, the
ultimate vacuum required will depend in practice on the nature and composition of the final gas mixture. Due
consideration should therefore be given to the partial pressure of the residual gas when the uncertainty in
the volume fraction of the calibration gas mixture is evaluated.
c) Close the shut-off valve between the vacuum pump and the reservoir and fill the reservoir with the
calibration component, to a pressure of approximately 110 kPa (1,1 bar). Re-evacuate and refill the
reservoir in the same manner. In the final filling operation, adjust the pressure of the calibration component
in the reservoir so that the over-pressure is sufficient for the syringe to be filled.
Make appropriate provision to ensure that hazardous gaseous components are vented safely from the
working area.
d) With the plunger pushed fully home, insert the needle of the empty metering syringe through the septum
(see Figure B.1) into the reservoir. Raise and lower the plunger several times to ensure that the syringe is
thoroughly flushed with the calibration component without any significant contamination.
e) Fill the syringe by fully withdrawing the plunger, then remove the syringe from the septum of the reservoir.
With the needle retained in position on the syringe, set the plunger to the first graduation mark and connect
the syringe to the mixing system (Figure B.2).
NOTE A convenient way by which to make the connection is again to use a septum.
In some cases, it is convenient to introduce the calibration component into the syringe in the liquid phase,
then allow it to evaporate after it has issued from the nozzle. The filling procedure is then straightforward but
precautions are still required to ensure that no significant amount of air or other contaminants are
introduced into the syringe with the liquid.
f) Pass the complementary gas through a pressure regulator and a shut-off valve to a conditioning train, which
may consist of a purifier and/or a humidifier and/or a heat exchange unit immersed in a thermostat bath as
required. (It may be the case that none of these components is required.)
g) Pass the conditioned gas stream through a calibrated flow meter to a gas-mixing vessel, which may be of
any suitable configuration, and at the input of which it meets the calibration component. Inject the calibration
component by means of the syringe, filled as described in e), equipped with a mechanically-driven plunger
and a variable speed motor, at the predetermined, constant speed.
4.2 Area of validity
The method is applicable to preparation of mixtures of non-reacting species, i.e. those which do not react with
any material of construction of the flow path of the complementary gas or that of the calibration component
being injected.
Particular care shall be exercised if the method is considered as a means of preparation of gaseous mixtures
which contain components that form potentially explosive mixtures in air. Steps shall be taken to ensure that the
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
apparatus is safe, for example by means of in-line flame arrestors in addition to the items mentioned in 4.1 and
listed in Figure B.2.
As is the case for the other dynamic mixing methods presented in ISO 6145, the effectiveness of the mixing
system to provide a homogeneous gas mixture shall be checked; it is not satisfactory to rely solely upon the
ratio of flow rates as the basis for expression of the gas composition, unless the method has been validated for
the gas mixture which is required.
4.3 Operating conditions
The general conditions common to all dynamic techniques of preparation shall be observed. Give careful
consideration to materials used in construction of the entire flow system. Use only materials which are of low
porosity and which are non-adsorbing. The pipe work shall be clean and all unions secure.
Any flow metering method may be used for the complementary gas provided that the range is appropriate and
the materials of construction are compatible with the mixture to be prepared. The complementary gas shall, in
any case, be free from particulates. This is especially important if the flow is measured by means of a variable-
area flowmeter, where there is no restriction between the float and the interior of the wall of the tube.
The capillary or syringe needle through which the calibration component is delivered shall be of length and
cross-section such that there is no measurable backpressure within the syringe at the fastest discharge rate for
which it is to be used. This requirement on dimensions applies equally to other parts of the flow paths so that no
pressure gradients are caused.
All parts of the apparatus shall be maintained at a uniform temperature.
Practical hints for application of the method are presented in Annex C.
5 Expression of results
5.1 Volume fraction
The volume fraction of calibration component AB in complementary gas is given by Equation (1), or, if the
calibration component is in the liquid state, by Equations (1) and (2).
The volume fraction is determined with reference to the methods of calibration described in ISO 6145-1. Due
consideration shall be given to the uncertainty associated with the method which is selected.
5.2 Sources of uncertainty
The fundamental sources of uncertainty are in the flow rate of the complementary gas, the determination of the
volume of the syringe and the rate of travel of the plunger in the syringe. The precautions presented under 4.3
shall be observed. Errors are introduced if there is backpressure in any part of the flow system, or if the gas
streams are not maintained at uniform temperature throughout. In particular, the syringe, during the filling
procedure, may have been at a temperature different from that of the rest of the apparatus; in all probability, it
will have been warmed by hand-contact. To reiterate the precaution given in 4.1.2, it is necessary to ensure that
the temperature of the syringe has returned to that of the rest of the apparatus before the gas mixture is
prepared.
If the motor used to drive the syringe is of the variable-frequency stepper type, the flow of gas may be pulsed
rather than being at steady, uniform flow. Attention is drawn to this here as a cautionary measure and means of
avoidance of this effect are given in Annex C.
Another possible source of uncertainty is inefficient mixing of the calibration component and the complementary
gas. The efficiency of mixing is checked by verification of the volume fraction by means of the comparison
method (see ISO 6143). This also serves to check the efficiency of vaporization in case of liquid injection. Refer
also to 5.3.
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
5.3 Uncertainty of volume fraction
The uncertainty in the volume fraction of the calibration component in the calibration mixture, at constant
temperature and pressure, is estimated from the separate uncertainties in the flow rates of the calibration
component and the complementary gas. It is necessary to take into account the sources of uncertainty given in
5.2 relative to individual flow rates.
The volume fraction of component A is given by Equation (1).
The relative expanded uncertainty in ϕ is then given by Equation (3):
A
1
� �
� � � � � �
2 2 2
U(ϕ ) 2q u(q ) u(q )
A B A B
= + (3)
ϕ q +q q q
A A B A B
[2]
NOTE The derivation of this formula is presented in Annex C of ISO 6145-7:2001 .
The root mean square (rms) sum of the standard uncertainty contributions is multiplied by the coverage factor
k = 2 to give a relative expanded uncertainty based on a level of confidence of approximately 95 %.
The standard uncertainty u(q ) in the flow rate of the complementary gas shall be obtained with reference to
B
ISO 6145-1 for the selected method of flow calibration.
This estimate of the relative uncertainty in the composition rests entirely on the uncertainties in the
measurements of flow rates. The other factor to be taken into account is the efficiency of mixing. To check the
effectiveness of a mixing system to provide a homogeneous calibration gas mixture, mixtures shall be prepared
by the method as described and the compositions shall be checked by the comparison method, specified in
ISO 6143. This procedure also identifies bias from other sources and establishes traceability against standard
mixtures.
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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
Annex A
(informative)
Pre-mixed gases for preparation of mixtures of high dilution
A.1 Calculation of results
If pre-mixed gases are used instead of pure gases, mixtures of higher dilution can be prepared. Calculation of
results relative to a binary mixture is then as below:
The volume fraction of component A in the final calibration gas mixture is given by Equation (A.1) (provided
there is no volume change on mixing):
� �� � ��
ϕ q +ϕ q ϕ q +ϕ q
M B M B
A A A A
ϕ = = (A.1)
A
q +q q
M B ϕ
where
�
ϕ is the volume fraction of A in the pre-mixed gas;
A
��
ϕ is the volume fraction of AB in the complementary gas, (this will normally be zero);
A
q is the volume flow rate of the pre-mixed gas;
M
q is the volume flow rate of the complementary gas B;
B
q is the volume flow rate of the calibration gas mixture.
ϕ
A.2 Uncertainty of volume fraction
It is necessary to take into account the uncertainties of the volume flow rates and the uncertainties of the
volume fractions of the calibration component in the pre-mixed gas and also in the complementary gas (if
relevant). Normally, the complementary gas will not contain the calibration component.
For the case in which the complementary gas does not contain the calibration component, A:
�
ϕ q
M
A
ϕ = (A.2)
A
q +q
A B
and the relative expanded uncertainty in the volume fraction ϕ is given by
A
1
� �
� � � � � � � �
2 2 2 2 2
�
U(ϕ ) 2q u(q ) u(q ) q +q u(ϕ
A B M B M B
A
= + + (A.3)
�
ϕ q +q q q q ϕ
A B M M B B
A
The derivation of Equation (A.3) is presented in ISO 6145-7:2001, Annex C. The rms sum of the standard
uncertainty contributions is multiplied by the coverage factor k = 2 to give a relative expanded uncertainty
based on a level of confidence of approximately 95 %. The uncertainty in the flow rate of the carrier gas is
obtained with reference to ISO 6145-1 for the selected method of flow calibration.
©
6 ISO 2004 – All rights reserved

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SIST EN ISO 6145-4:2008
ISO 6145-4:2004(E)
Annex B
(informative)
Example of apparatus for preparation of calibration gas mixtures
A schema of an apparatus for filling a syringe with a gaseous calibration component is given in Figure B.1. The
reservoir should be capable of operation up to a pressure of 140 kPa (1,4 bar). A pressure gauge to measure
pressures from 10 kPa (0,1 bar) to 200 kPa (2 bar) to an uncertainty of 1
...