1、 Reference number ISO 29473:2010(E) ISO 2010INTERNATIONAL STANDARD ISO 29473 First edition 2010-12-01 Fire tests Uncertainty of measurements in fire tests Essais au feu Incertitude de mesures dans les essais au feu ISO 29473:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In acc
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6、ffice 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 2010 All rights reservedISO 29473:2010(E) ISO 2010 All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative referen
7、ces1 3 Terms, definitions and symbols 2 3.1 Terms and definitions .2 3.2 Symbols3 4 Principles .4 5 Evaluating standard uncertainty5 5.1 General .5 5.2 Type A evaluation of standard uncertainty.6 5.3 Type B evaluation of standard uncertainty.6 5.4 Accounting for multiple sources of error .7 6 Determ
8、ining combined standard uncertainty.7 7 Determining expanded uncertainty .8 8 Reporting uncertainty .9 9 Summary of procedure for evaluating and expressing uncertainty 10 Annex A (informative) Basic concepts of measurement uncertainty11 Annex B (informative) Uncertainty of fire test results.13 Annex
9、 C (informative) Example of estimating the uncertainty in heat release measurements in the cone calorimeter14 Bibliography23 ISO 29473:2010(E) iv ISO 2010 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
10、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, govern
11、mental 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 Di
12、rectives, 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 b
13、odies 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 29473 was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommit
14、tee SC 1, Fire initiation and growth. ISO 29473 is based, with the permission of ASTM International, on ASTM E 2536 Standard Guide for Assessment of Measurement Uncertainty in Fire Tests, copyright ASTM International. ISO 29473:2010(E) ISO 2010 All rights reserved vIntroduction Users of fire test da
15、ta often need a quantitative indication of the quality of the data presented in a test report. This quantitative indication is referred to as the “measurement uncertainty”. There are two primary reasons for estimating the uncertainty of fire test results: ISO/IEC 17025 requires that competent testin
16、g and calibration laboratories include uncertainty estimates for the results that are presented in a report. Fire safety engineers need to know the quality of the input data used in an analysis to determine the uncertainty of the outcome of the analysis. General principles for evaluating and reporti
17、ng measurement uncertainties are described in ISO/IEC Guide 98-3:2008. Application of ISO/IEC Guide 98-3:2008 to fire test data presents some unique challenges. This International Standard shows how these challenges can be overcome. INTERNATIONAL STANDARD ISO 29473:2010(E) ISO 2010 All rights reserv
18、ed 1Fire tests Uncertainty of measurements in fire tests 1 Scope This International Standard gives guidance on the evaluation and expression of uncertainty of fire test method measurements developed and maintained by ISO/TC 92, based on the approach presented in ISO/IEC Guide 98-3. Application of th
19、is International Standard is limited to tests that provide quantitative results in engineering units. This includes, for example, methods for measuring the heat release rate of burning specimens based on oxygen consumption calorimetry, as in ISO 5660-1:2002. This International Standard does not appl
20、y to tests that provide results in the form of indices or binary results (e.g. pass/fail). In some cases, additional guidance will be required to supplement this International Standard. For example, the expression and use of uncertainty at low levels may require additional guidance and uncertainties
21、 associated with sampling are not explicitly addressed. NOTE 1 The procedures described in this International Standard involve some complex mathematics. Basic concepts of measurement uncertainty are provided in Annex A. NOTE 2 The guidelines presented in this International Standard may also be used
22、to evaluate and express the uncertainty associated with fire test results. However, it is not always possible to quantify the uncertainty of fire test results as some sources of uncertainty cannot be accounted for. 2 Normative references The following referenced documents are indispensable for the a
23、pplication 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 5660-1:2002, Reaction-to-fire tests Heat release, smoke production and mass loss rate Part 1: Heat release
24、rate (cone calorimeter method) ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method ISO 13943, Fire safety Vocabulary ISO/IEC 17025:2005, General requirem
25、ents for the competence of testing and calibration laboratories ISO/IEC Guide 98-3:2008, Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) ISO/IEC Guide 99:2007, International vocabulary of metrology Basic and general concepts and associated terms (V
26、IM) ISO 29473:2010(E) 2 ISO 2010 All rights reserved3 Terms, definitions and symbols For the purposes of this document, the following terms, definitions and symbols apply. 3.1 Terms and definitions 3.1.1 measurement uncertainty uncertainty of measurement uncertainty non-negative parameter characteri
27、zing the dispersion of the quantity values being attributed to a measurand, based on the information used NOTE Adapted from ISO/IEC Guide 99:2007: the Notes are not included here. 3.1.2 standard measurement uncertainty standard uncertainty of measurement standard uncertainty measurement uncertainty
28、expressed as a standard deviation ISO/IEC Guide 99:2007, definition 2.30 3.1.3 Type A evaluation of measurement uncertainty Type A evaluation evaluation of a component of measurement uncertainty by a statistical analysis of measured quantity values obtained under defined measurement conditions NOTE
29、Adapted from ISO/IEC Guide 99:2007: the Notes are not included here. 3.1.4 Type B evaluation of measurement uncertainty Type B evaluation evaluation of a component of measurement uncertainty determined by means other than a Type A evaluation of measurement uncertainty NOTE Modified from ISO/IEC Guid
30、e 99:2007: the Example and Note are not included here. 3.1.5 combined standard measurement uncertainty combined standard uncertainty standard measurement uncertainty that is obtained using the individual standard measurement uncertainties associated with the input quantities in a measurement model I
31、SO/IEC Guide 99:2007, definition 2.31 3.1.6 expanded measurement uncertainty expanded uncertainty product of a combined standard measurement uncertainty and a coverage factor one NOTE Adapted from ISO/IEC Guide 99:2007: the Notes are not included here and the definition is slighty modified. ISO 2947
32、3:2010(E) ISO 2010 All rights reserved 33.1.7 coverage factor number larger than one by which a combined standard measurement uncertainty is multiplied to expand the coverage probability to a specified value NOTE 1 A coverage factor is usually symbolized k (see also ISO/IEC Guide 98-3:2008, 2.3.6).
33、NOTE 2 Adapted from ISO/IEC Guide 99:2007. 3.2 Symbols C cone calorimeter orifice coefficient (m 1/2 kg 1/2 K 1/2 ) c isensitivity coefficient of X if functional relationship between the measurand and the input quantities (Equation 2) k coverage factor m number of sources of error affecting the unce
34、rtainty of X i(Equation 8) N number of input quantities n number of observations or measurements Q y is the measured value of the measurand; Y is the true value of the measurand. All terms in Equation (1) have the units of the physical quantity that is measured. This equation cannot be used to deter
35、mine the error of a measurement because the true value is unknown, otherwise a measurement would not be needed. In fact, the true value of a measurand is unknown because it cannot be measured without error. However, it is possible to estimate, with some confidence, the expected limits of error. This
36、 estimate is referred to as the “uncertainty of measurement” and provides a quantitative indication of its quality. Errors of measurement may have two components, a random component and a systematic component. The former is due to a number of sources that affect a measurement in a random and uncontr
37、olled manner. Random errors cannot be eliminated, but their effect on uncertainty may be reduced by increasing the number of repeat measurements and by applying a statistical analysis to the results. Systematic errors remain unchanged when a measurement is repeated under the same conditions. Their e
38、ffect on uncertainty cannot be completely eliminated either, but it can be reduced by applying corrections to account for the error contribution due to recognized systematic effects. The residual systematic error is unknown and may be treated as a random error for the purpose of this International S
39、tandard. ISO 29473:2010(E) ISO 2010 All rights reserved 55 Evaluating standard uncertainty 5.1 General A quantitative result of a fire test Y is not normally obtained from a direct measurement, but is determined as a function (f) from N input quantities X 1 , X 2 , , X N : 12 (,) N YfXX X = L (2) wh
40、ere Y is measurand; f is the functional relationship between the measurand; X iis input quantities (i = 1 N). The input quantities may be categorized as quantities whose values and uncertainties are: directly determined from single observation, repeated observation or judgment based on experience; o
41、r brought into the measurement from external sources such as reference data obtained from handbooks. An estimate of the output, y, is obtained from Equation (2) using input estimates x 1 , x 2 , , x Nfor the values of the N input quantities: 12 (,) N yfxx x = L (3) Substituting Equations (2) and (3)
42、 into Equation (1) leads to: 12 N yY Y =+=+ L (4) where iis the contribution to the total measurement error from the error associated with the input estimate x i . A possible approach to determine the uncertainty of y involves a large number (n) of repeat measurements. The mean value of the resultin
43、g distribution () y is the best estimate of the measurand. The experimental standard deviation of the mean is the best estimate of the standard uncertainty of y, denoted by u(y): 2 2 2 1 () () () () (1 ) n k k yy sy uy s y nn n = = (5) where u is standard uncertainty; s is the experimental standard
44、deviation; n is the number of observations; y kis the k thmeasured value; y is the mean of n measurements. ISO 29473:2010(E) 6 ISO 2010 All rights reservedThe number of observations n should be large enough to ensure that y provides a reliable estimate of the expectation yof the random variable y, a
45、nd that s 2 () y provides a reliable estimate of the variance 22 () () /. yy = n NOTE If the probability distribution of y is normal, then the standard deviation of s () y relative to () y is approximately 2(n 1 ) 1/2 . Thus, for n = 10 the relative uncertainty of () s y is 24 percent, while for n =
46、 50 it is 10 percent. Additional values are given in Table E.1 in ISO/IEC Guide 98-3:2008. Unfortunately, it is often not feasible or even possible to perform a sufficiently large number of repeat measurements. In those cases, the uncertainty of the measurement can be determined by combining the sta
47、ndard uncertainties of the input estimates. The standard uncertainty of an input estimate x iis obtained from the distribution of possible values of the input quantity X i . There are two types of evaluations depending on how the distribution of possible values is obtained. 5.2 Type A evaluation of
48、standard uncertainty A Type A evaluation of standard uncertainty of x iis based on the frequency distribution, which is estimated from a series of n repeated observations x i,k(k = 1 n). The resulting equation is similar to Equation (5): 2 , 2 2 1 () () () () (1 ) n ik i ik ii xx sx ux s x nn n = =
49、(6) where x i,kis the k thmeasured value; i x is the mean of n measurements. NOTE Type A evaluations of standard uncertainty are rare in fire tests as repeated measurements are not common. 5.3 Type B evaluation of standard uncertainty A Type B evaluation of standard uncertainty of x iis not based on repeated measurements but on an a priori frequency distribution. In this case the uncertainty is determined from previous measurement data, experience or general knowledge, man
