SIST EN ISO 6145-7:2011

Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 7: Thermal mass-flow controllers (ISO 6145-7:2009)

This part of ISO 6145 is one of a series of International Standards dealing with dynamic volumetric methods used for the preparation of calibration gas mixtures. This part specifies a method for continuous production of calibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by use of commercially available thermal mass-flow controllers. If this method is employed for the preparation of calibration gas mixtures, the optimum performance is as follows: the relative expanded uncertainty of measurement, U, obtained by multiplying the combined standard uncertainty by a coverage factor k = 2, is not greater than 2 %. If pre-mixed gases are used instead of pure gases, mole fractions below 10-6 can be obtained. The measurement of mass flow is not absolute and the flow controller requires independent calibration. The merits of the method are that a large quantity of the gas mixture can be prepared on a continuous basis and that multicomponent mixtures can be prepared as readily as binary mixtures if the appropriate number of thermal mass-flow controllers is utilized.

Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 7: Thermische Massendurchflussregler (ISO 6145-7:2009)

Dieser Teil von ISO 6145 ist Teil einer Reihe Internationaler Normen, die die verschiedenen dynamisch-volumetrischen Verfahren zur Herstellung von Kalibriergasgemischen behandelt. Der vorliegende Teil legt ein Verfahren zur kontinuierlichen Herstellung von Kalibriergasgemischen mit zwei oder mehr Komponenten aus reinen Gasen oder anderen Gasgemischen mithilfe handelsüblicher thermischer Massendurchflussregler fest.
Wird dieses Verfahren zur Herstellung von Kalibriergasgemischen angewendet, ist die optimale Leistung wie folgt: die relative erweiterte Messunsicherheit U, die durch Multiplizieren der kombinierten Standardunsicherheit mit einem Überdeckungsfaktor von k = 2 erhalten wird, ist nicht größer als 2 %.
Werden anstelle reiner Gase Gasvorgemische verwendet, können Molfraktionen unter 10–6 erreicht werden. Die Messung des Massenstroms ist nicht absolut und für den Massendurchflussregler ist eine unabhängige Kalibrierung erforderlich.
Die Vorzüge dieses Verfahrens bestehen darin, dass eine große Menge des Gasgemischs auf einer kontinuierlichen Grundlage hergestellt werden kann und dass Mehrkomponentengemische genauso leicht herzustellen sind wie binäre Gemische, sofern die entsprechende Anzahl thermischer Massendurchflussregler eingesetzt wird.
ANMERKUNG   Gasmischsysteme auf der Grundlage thermischer Massendurchflussregler, die zum Teil die Möglichkeit einer Computersteuerung oder automatischen Steuerung einschließen, sind im Handel erhältlich.

Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de méthodes volumétriques dynamiques - Partie 7: Régulateurs thermiques de débit massique (ISO 6145-7:2009)

L'ISO 6145‑7:2009 spécifie une méthode de production continue de mélanges de gaz pour étalonnage à au moins deux constituants, à partir de gaz purs ou d'autres mélanges de gaz, en utilisant les régulateurs thermiques de débit massique disponibles sur le marché.
Si cette méthode est employée pour la préparation de mélanges de gaz pour étalonnage, la performance optimale est la suivante: l'incertitude élargie relative de mesurage, U, obtenue en multipliant l'incertitude type composée par un facteur d'élargissement k = 2, n'est pas supérieure à 2 %.
Si l'on utilise des gaz mélangés au préalable à la place des gaz purs, il est possible d'obtenir des fractions molaires inférieures à 10-6. Le mesurage du débit massique n'étant alors pas suffisamment précis, le régulateur de débit doit faire l'objet d'un étalonnage indépendant.
Cette méthode a pour principal mérite de permettre la préparation en continu d'un mélange de gaz en grande quantité ainsi que de rendre la préparation de mélanges à plusieurs constituants aussi simple que celle de mélanges ne comptant que deux constituants, à condition d'utiliser le bon nombre de régulateurs thermiques de débit massique.

Analiza plinov - Priprava kalibracijskih plinskih zmesi z uporabo dinamičnih volumetričnih metod - 7. del: Termični regulatorji masnega pretoka (ISO 6145-7:2009)

Ta del ISO 6145 je eden izmed serij mednarodnih standardov, ki se ukvarjajo z dinamičnimi volumetričnimi tehnikami, uporabljenimi za pripravo kalibracijskih plinskih zmesi. Ta del določa metodo za neprekinjeno proizvodnjo kalibracijskih plinskih zmesi, ki vsebujejo dve ali več sestavin, iz čistih plinov ali drugih plinskih zmesi z uporabo komercialno dostopnih termičnih regulatorjev masnega pretoka. Če je ta metoda uporabljena za pripravo kalibracijskih plinskih zmesi, je optimalno delovanje naslednje: negotovost relativnega širjenja meritve U, pridobljene z množenjem združene standardne negotovosti s faktorjem pokritja k = 2, ki ni večji kot 2 %. Če so uporabljeni vnaprej zmešani plini namesto čistih plinov, lahko dosežemo molske frakcije pod 10–6. Meritev pretoka mase ni absolutna in regulator masnega pretoka potrebuje neodvisno kalibracijo. Odlike te metode so, da je lahko večja količina plinske zmesi pripravljena neprekinjeno in da so lahko večkomponentne zmesi pripravljene enako hitro kot binarne zmesi, če je uporabljeno primerno število termičnih regulatorjev masnega pretoka.

General Information

• Status: Withdrawn
• Publication Date: 08-Feb-2011
• Withdrawal Date: 27-Jan-2019
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: NAD - Petroleum products, lubricants and related products
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 24-Jan-2019
• Due Date: 16-Feb-2019
• Completion Date: 28-Jan-2019
• Ref Project: EN ISO 6145-7:2010 - Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 7: Thermal mass-flow controllers (ISO 6145-7:2009)

Relations

• Replaced By: SIST EN ISO 6145-7:2019 - Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7: Thermal mass-flow controllers (ISO 6145-7:2018)
• Effective Date: 01-Mar-2019

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 6145-7:2011
01-marec-2011
$QDOL]DSOLQRY3ULSUDYDNDOLEUDFLMVNLKSOLQVNLK]PHVL]XSRUDERGLQDPLþQLK
YROXPHWULþQLKPHWRGGHO7HUPLþQLUHJXODWRUMLPDVQHJDSUHWRND,62

Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods
- Part 7: Thermal mass-flow controllers (ISO 6145-7:2009)
Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-
volumetrischen Verfahren - Teil 7: Thermische Massendurchflussregler (ISO 6145-
7:2009)
Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de
méthodes volumétriques dynamiques - Partie 7: Régulateurs thermiques de débit
massique (ISO 6145-7:2009)
Ta slovenski standard je istoveten z: EN ISO 6145-7:2010
ICS:
71.040.40 Kemijska analiza Chemical analysis
SIST EN ISO 6145-7:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 6145-7:2011

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SIST EN ISO 6145-7:2011


EUROPEAN STANDARD
EN ISO 6145-7

NORME EUROPÉENNE

EUROPÄISCHE NORM
December 2010
ICS 71.040.40
English Version
Gas analysis - Preparation of calibration gas mixtures using
dynamic volumetric methods - Part 7: Thermal mass-flow
controllers (ISO 6145-7:2009)
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 7:
dynamiques - Partie 7: Régulateurs thermiques de débit Thermische Massendurchflussregler (ISO 6145-7:2009)
massique (ISO 6145-7:2009)
This European Standard was approved by CEN on 11 December 2010.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6145-7:2010: E
worldwide for CEN national Members.

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SIST EN ISO 6145-7:2011
EN ISO 6145-7:2010 (E)
Contents Page
Foreword .3

2

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SIST EN ISO 6145-7:2011
EN ISO 6145-7:2010 (E)
Foreword
The text of ISO 6145-7:2009 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 6145-7:2010.
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 June 2011, and conflicting national standards shall be withdrawn at
the latest by June 2011.
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, Croatia, 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 6145-7:2009 has been approved by CEN as a EN ISO 6145-7:2010 without any modification.

3

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SIST EN ISO 6145-7:2011

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SIST EN ISO 6145-7:2011

INTERNATIONAL ISO
STANDARD 6145-7
Second edition
2009-04-01

Gas analysis — Preparation of calibration
gas mixtures using dynamic volumetric
methods —
Part 7:
Thermal mass-flow controllers
Analyse des gaz — Préparation des mélanges de gaz pour étalonnage
à l'aide de méthodes volumétriques dynamiques —
Partie 7: Régulateurs thermiques de débit massique




Reference number
ISO 6145-7:2009(E)
©
ISO 2009

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)
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All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
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Published in Switzerland

ii © ISO 2009 – All rights reserved

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 2
5 Set-up. 2
5.1 General. 2
5.2 Thermal mass-flow controller using a constant current supply. 2
5.3 Thermal mass-flow controller under constant temperature control . 3
6 Preparation of gas mixtures . 4
6.1 Description of the experimental procedure .4
6.2 Area of validity . 6
6.3 Operating conditions. 6
7 Calculations. 7
7.1 Volume fraction. 7
7.2 Sources of uncertainty. 7
7.3 Uncertainty of measurement . 8
Annex A (informative) Pre-mixed gases for preparation of mixtures of high dilution . 9
Annex B (informative) Practical hints. 10
Annex C (informative) Calculation of uncertainties. 12
Bibliography . 15

© ISO 2009 – All rights reserved iii

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(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 6145-7 was prepared by Technical Committee ISO/TC 158, Analysis of gases.
This second edition cancels and replaces the first edition (ISO 6145-7:2001). In preparation of the first edition,
it was assumed that each thermal mass-flow controller (TMC) would be configured for use at its optimum
performance, and the uncertainty in the method was estimated on that basis. In this edition, therefore, extra
precautionary text has been added to make it clear that the method shall not be employed, for example, to
make a 10:1 binary mixture by using two thermal mass-flow controllers of identical range with one operated at
its maximum, say, of 1 000 ml/min and the other at 100 ml/min. In the first edition, this necessary provision
was only stated briefly in an informative annex; it has now been expanded and stated more explicitly in a
normative part. Another major update is separation of the original Clause 3 into two clauses, one of which
(Clause 4) defines the principle while the other (Clause 5) presents additional explanation to the user. The
latter of these clauses now includes the necessary requirements. By introducing two new and relevant
bibliographic references, the understanding of Annex B has been improved. Finally, some typing errors have
been corrected.
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 stream, has been withdrawn.
iv © ISO 2009 – All rights reserved

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SIST EN ISO 6145-7:2011
INTERNATIONAL STANDARD ISO 6145-7:2009(E)

Gas analysis — Preparation of calibration gas mixtures using
dynamic volumetric methods —
Part 7:
Thermal mass-flow controllers
1 Scope
This part of ISO 6145 is one of a series of International Standards dealing with dynamic volumetric methods
used for the preparation of calibration gas mixtures. This part specifies a method for continuous production of
calibration gas mixtures, containing two or more components, from pure gases or other gas mixtures by use of
commercially available thermal mass-flow controllers.
If this method is employed for the preparation of calibration gas mixtures, the optimum performance is as
follows: the relative expanded uncertainty of measurement, U, obtained by multiplying the combined standard
uncertainty by a coverage factor k = 2, is not greater than 2 %.
−6
If pre-mixed gases are used instead of pure gases, mole fractions below 10 can be obtained. The
measurement of mass flow is not absolute and the flow controller requires independent calibration.
The merits of the method are that a large quantity of the gas mixture can be prepared on a continuous basis
and that multicomponent mixtures can be prepared as readily as binary mixtures if the appropriate number of
thermal mass-flow controllers is utilized.
NOTE Gas-blending systems based upon thermal mass-flow controllers, some including the facility of
computerization and automatic control, are commercially available.
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 6145-1:2003, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods —
Part 1: Methods of calibration
ISO 7504, Gas analysis — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7504 apply.

© ISO 2009 – All rights reserved 1

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)
4 Principle
Continuous production of calibration gas mixtures, containing two or more components, from pure gases or
other gas mixtures by the use of commercially available thermal mass-flow controllers is described. By
adjusting the set-points on the flow controllers to pre-determined values, it is possible to change the
composition of the gas mixture rapidly and in a continuously variable manner. By selecting appropriate
combinations of thermal mass-flow controllers and with the use of pure gases, the volume fraction of the
component of interest in the complementary gas can be varied by a factor of 1 000.
5 Set-up
5.1 General
To prepare the gas mixture, each gaseous component is passed at a known, controlled flow rate, and at
constant pressure, from a calibrated thermal mass-flow controller. Use accurate flowmeters in measuring the
relevant flows in order to reach an acceptable measure of uncertainty regardless of the setting of the
mass-flow controller (see also ISO 6145-1:2003, Table 1).
A thermal mass-flow controller consists of a measuring unit for mass flow and a proportioning valve which is
controlled by an electronic unit (see also References [1] and [2]).
5.2 Thermal mass-flow controller using a constant current supply
The flowing gas is passed through a heater connected to a constant current supply and the temperature is
sensed upstream and downstream from the heater.
Figure 1 shows the principle of a thermal mass-flow controller: heater, temperature sensors and associated
circuitry. The two temperature sensors, one upstream and one downstream from the heater form two arms of
a Wheatstone bridge circuit, which is balanced to give a zero reading when there is no gas flow. When there is
a gas flow through the system, a temperature difference, ∆T, is established between the two sensors such that
the heat flux, Φ, is given by:
Φ=∆cTq (1)
pm
where
c is the heat capacity per unit mass, or molar heat capacity, of the gas at constant pressure;
p
q is the mass flow rate.

m
2 © ISO 2009 – All rights reserved

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)

Key
1 temperature sensor 1
2 temperature sensor 2
3 heater
4 gas supply
5 current supply
6 Wheatstone bridge
7 differential amplifier
8 signal readout
Figure 1 — Principle of a thermal mass-flow controller with constant current supply
The difference in temperature between sensors results in a potential difference across the Wheatstone bridge
circuit and thus a signal. The signal is compared with an adjustable reference voltage in a differential amplifier.
The resulting output signal is in turn used for operating a control valve to regulate the flow of gas.
5.3 Thermal mass-flow controller under constant temperature control
In this system (see Figure 2), the gas passes through three heaters in sequence, each of which is connected
to an arm of a self-regulating Wheatstone bridge. Instead of the difference in temperature being measured,
the input to each heater is such that the temperature distribution along the flow path is maintained uniform.
The Wheatstone bridge current is proportional to the heat loss and therefore proportional also to the mass
flow of the gas. The output signal is again used to operate a solenoid valve to control the mass flow rate.
© ISO 2009 – All rights reserved 3

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)

Key
1 heater 1
2 heater 2
3 heater 3
4 gas supply
5 current supply
6 Wheatstone bridge
7 differential amplifier
8 signal readout
Figure 2 — Thermal mass-flow controller under constant temperature control
In the preparation of multicomponent mixtures, it is in general necessary to use one mass-flow controller for
each component. Dual-channel controllers are available and may be used in the preparation of binary
mixtures or, for example, in the preparation of mixtures of a given gas in air.
6 Preparation of gas mixtures
6.1 Description of the experimental procedure
A schematic diagram of the arrangement used for the preparation of binary mixtures is shown in Figure 3.
The pressure and temperature at the time of the calibration shall be recorded.
Depending on the gases to be mixed and the fact that they are not ideal, the volume fraction can be
somewhat influenced by the ambient pressure and temperature. The pressure and temperature at the time of
calibration of the analyser should be as near as possible to those prevalent at the time the thermal mass-flow
controllers were checked by the comparison method given in ISO 6143 (see 7.3).
Concentrations of calibration gas mixtures are normally expressed as volume fractions but manufacturers’
accuracy specifications for thermal mass-flow controllers are expressed in terms of percentage of the full
scale of the instrument. The relative expanded uncertainty of 2 %, which is quoted in the scope of this part of
ISO 6145, is 2 % of the volume fraction of the calibration component of the mixture. This value assumes
optimum use of each thermal mass-flow controller in the system, which means that each is operated at, or
4 © ISO 2009 – All rights reserved

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SIST EN ISO 6145-7:2011
ISO 6145-7:2009(E)
very near to, its maximum flow rate. Thus, if a thermal mass-flow controller is operate
...