1、 Reference number ISO/TS 14167:2003(E) ISO 2003TECHNICAL SPECIFICATION ISO/TS 14167 First edition 2003-04-15 Gas analysis General quality assurance aspects in the use of calibration gas mixtures Guidelines Analyse des gaz Aspects gnraux de lassurance qualit dans lutilisation de mlanges de gaz pour t
2、alonnage Lignes directrices ISO/TS 14167:2003(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer p
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5、al Secretariat at the address given below. ISO 2003 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at
6、 the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2003 All rights reservedISO/TS 14167:2003(E) ISO 2003 Al
7、l rights reserved iiiContents Page Foreword iv Introduction ivi 1 Scope 1 2 Terms and definitions. 1 3 Gas analysis using a comparison method. 4 4 Uncertainty. 4 4.1 General. 4 4.2 Step-by-step approach . 5 4.3 Direct approach. 6 5 Traceability 7 5.1 General. 7 5.2 Calibration for response function
8、determination 8 5.3 Calibration for bias detection and correction 8 5.4 Verification of individual results . 8 5.5 Traceability of reference values 9 6 Validation and verification . 9 6.1 Validation of methods. 9 6.2 Verification of individual results . 10 7 Documentation 10 Annex A (informative) Ex
9、amples where traceable standards are available . 11 Annex B (informative) Example where traceable standards are not available. 16 Annex C (informative) Hierarchy of reference gas mixtures 18 Bibliography . 22 ISO/TS 14167:2003(E) iv ISO 2003 All rights reservedForeword ISO (the International Organiz
10、ation 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
11、 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. I
12、nternational 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. Publ
13、ication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a technical committee may decide to publish other types of normative document: an ISO Publi
14、cly Available Specification (ISO/PAS) represents an agreement between technical experts in an ISO working group and is accepted for publication if it is approved by more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement b
15、etween the members of a technical committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revised to become an Inte
16、rnational Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an International Standard or be withdrawn. Attention is drawn to the possibility that some of the elements of this document may
17、be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TS 14167 was prepared by Technical Committee ISO/TC 158, Analysis of gases. ISO/TS 14167:2003(E) ISO 2003 All rights reserved vIntroduction Gas analyses are performed on samples cove
18、ring a wide range of compositions. All gas analyses fall into one of two categories: those for which calibration gas mixtures exist with compositions that are traceable to reference gas mixtures (e.g. primary or national standards); those for which the above do not exist. In both cases, this Technic
19、al Specification provides the overall guidance on quality assurance aspects required to achieve a result with a valid measurement uncertainty. It is applicable only to calibration gas mixtures of gaseous, or totally vaporized, components which do not react with each other or with the cylinder walls.
20、 The user of this Technical Specification chooses, prior to any analyses, an appropriate measurement procedure depending on the application of the final results of the analyses and the requirements for a particular measurement uncertainty. This use may vary considerably, ranging from qualitative ana
21、lysis to accurate quantitative analysis for which evidence has to be provided that claimed measurement uncertainty levels are met. Each type of measurement procedure involves a number of issues, which are considered beforehand. Typically, for gas analysis these include: a) sampling; b) selection and
22、 use of calibration gas mixtures; c) selection and validation of measurement method; d) identification of uncertainty sources; e) quantification of uncertainty contributions; f) documentation. For a given measurement procedure, the effect of the above issues, influencing the uncertainty of the final
23、 measurement result, is calculated approximately. This may imply that several calculations have to be made in advance, with different sets of values for the parameters involved, before the required level of uncertainty is achieved. In practice, this calculation process is repeated until the desired
24、target uncertainty is reached. This process of defining target uncertainties is an effective way of finding correct solutions for specific measurement procedures. The final analysis is then performed using this evaluated procedure. To illustrate the use of this Technical Specification, two practical
25、 examples are given in Annex A. Annex B gives information on the validation of reference gas mixtures in those cases where calibration gases of widely acknowledged composition do not exist. Annex C describes the traditional hierarchy of reference gas mixtures. The references are given in the Bibliog
26、raphy. TECHNICAL SPECIFICATION ISO/TS 14167:2003(E) ISO 2003 All rights reserved 1Gas analysis General quality assurance aspects in the use of calibration gas mixtures Guidelines 1 Scope This Technical Specification provides guidance on the quality aspects in the field of gas analysis that are imple
27、mented in order to achieve a result with a valid measurement uncertainty. It provides guidelines on quality aspects to be employed in gas analysis using calibration gas mixtures and their subsequent validation and/or verification, and the testing of the analytical performance of gas analysis instrum
28、ents. These guidelines have the overall objective of defining procedures which will ensure that measurements of gas composition are reliable, comparable and consistent between different organizations and countries. This Technical Specification explains, in particular, the concepts of measurement unc
29、ertainty and of traceability as effective quality assurance tools for defining the measurement uncertainty of particular measurement results. It also gives guidance on how to identify and estimate measurement uncertainty components of the result, and how to combine these uncertainty components in or
30、der to obtain the overall uncertainty. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 traceability property of a result of a measurement or the value of a standard whereby it can be related to stated references, usually national or internati
31、onal standards, through an unbroken chain of comparisons all having stated uncertainties NOTE 1 The unbroken chain of comparisons is called a “traceability chain”. NOTE 2 A calibration gas mixture is traceable at best to a primary reference gas mixture. VIM1 2.2 uncertainty (of measurement) paramete
32、r, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand NOTE 1 The parameter may be, for example, a standard deviation or a given multiple of it, or the half-width of an interval having a stated level of con
33、fidence. NOTE 2 Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of series of measurements and can be characterized by experimental standard deviations. The other components, which can also b
34、e characterized by standard deviations, are evaluated from assumed probability distributions based on experience or other information. ISO/TS 14167:2003(E) 2 ISO 2003 All rights reservedNOTE 3 It is understood that the result of the measurement is the best estimate of the value of the measurand, and
35、 that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion. NOTE 4 Uncertainty can be expressed as a standard uncertainty or, when multiplied by a coverage factor, as an ex
36、panded uncertainty. Adapted from GUM2 2.3 uncertainty of a certified value estimate attached to a certified value of a quantity which characterizes the range of values within which the “true value” is asserted to lie with a stated level of confidence ISO Guide 30:19923 2.4 calibration gas mixture ga
37、s mixture of sufficient stability and homogeneity whose composition is properly established for use in the calibration of a measuring instrument or for the validation of a measurement or gas analytical method NOTE Calibration gas mixtures are the analogues of measurement standards in physical metrol
38、ogy ISO 7504:20014 2.5 reference gas mixture calibration gas mixture whose composition is sufficiently well established and stable to be used as a reference standard of composition from which other composition data are derived NOTE Reference gas mixtures are the analogues of reference standards. ISO
39、 7504:20014 2.6 primary reference gas mixture reference gas mixture which is designated, or generally accepted, as realizing a specific composition of the highest metrological quality NOTE 1 Primary reference gas mixtures are the analogues of primary standards. NOTE 2 Normally the use of primary ref
40、erence gas mixtures is confined to comparisons with other primary reference gas mixtures of similar compositions and to secure secondary reference gas mixtures by comparison. NOTE 3 Primary reference gas mixtures are sometimes designated as measurement standards by national metrology institutes, and
41、 may then be known as primary standard gas mixtures ISO 7504:20014 2.7 secondary reference gas mixture reference gas mixture whose composition is assigned by comparison with a primary reference gas mixture of similar composition, or with several such primary reference gas mixtures NOTE 1 Secondary r
42、eference gas mixtures are the analogues of secondary standards. NOTE 2 A secondary reference gas mixture may be used as a calibration gas mixture then having traceability to a primary reference gas mixture. ISO 7504:20014 ISO/TS 14167:2003(E) ISO 2003 All rights reserved 32.8 stability attribute of
43、a gas mixture, stored or used under specified conditions, to maintain its composition within its specified uncertainty limits for a specified period of time (maximum storage life) and over a specified range of pressure and of temperature NOTE It is appropriate to specify the uncertainty limits for e
44、ach component of interest. ISO 7504:20014 2.9 homogeneity state of a gas mixture wherein all of its components are distributed uniformly throughout the volume occupied by the gas mixture NOTE Unless any other indication is given, it is normally to be assumed that the gas mixture is homogeneous in co
45、mposition in time and space within the gas mixture. ISO 7504:20014 2.10 validation confirmation, through the provision of objective evidence, that the requirements for a specific intended use or application have been fulfilled NOTE 1 In design and development, validation concerns the process of exam
46、ining a product to determine conformity with user requirements. NOTE 2 Validation is normally performed on the final product under defined operating conditions. It may be necessary in earlier stages. NOTE 3 The term “validated” is used to designate the corresponding status. NOTE 4 Multiple validatio
47、ns may be carried out if there are different intended uses. NOTE 5 In gas composition analysis, validation refers to the confirmation that the method, as applied, is fit for the intended purpose. Adapted from ISO 7504:20014 2.11 verification Confirmation, through the provision of objective evidence,
48、 that the specified requirements have been fulfilled NOTE 1 In design and development, verification concerns the process of examining the result of a given activity to determine the conformity with the stated requirements for that activity. NOTE 2 The term “verified” is used to designate the corresp
49、onding status. NOTE 3 In gas composition analysis, verification refers to an individual result that agrees with the result of an independent method. ISO 7504:20014 ISO/TS 14167:2003(E) 4 ISO 2003 All rights reserved3 Gas analysis using a comparison method The acceptability of individual measurement results is improved when rigorous quality control provides evidence that the results are in agreement with results from: a) measurements on similar samples by other laboratories
