1、BRITISH STANDARDBS EN 60068-3-11: 2007Environmental testing Part 3-11: Supporting documentation and guidance Calculation of uncertainty of conditions in climatic test chambersThe European Standard EN 60068-3-11:2007 has the status of a British StandardICS 19.040g49g50g3g38g50g51g60g44g49g42g3g58g44g
2、55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 60068-3-11:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2
3、007 BSI 2007ISBN 978 0 580 54295 4National forewordThis British Standard is the UK implementation of EN 60068-3-11:2007. It is identical to IEC 60068-3-11:2007.The UK participation in its preparation was entrusted to Technical Committee GEL/104, Environmental conditions, classification and testing.A
4、 list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from l
5、egal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 60068-3-11 NORME EUROPENNE EUROPISCHE NORM June 2007 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische
6、 Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 60068-3-11:2007 E ICS 19.040 English version Environmental testing - Part 3-11: Supporting documentation and
7、guidance - Calculation of uncertainty of conditions in climatic test chambers (IEC 60068-3-11:2007) Essais denvironnement - Partie 3-11: Documentation daccompagnement et guide - Calcul de lincertitude des conditions en chambres dessais climatiques (CEI 60068-3-11:2007) Umgebungseinflsse - Teil 3-11:
8、 Untersttzende Dokumentation und Leitfaden - Berechnung der Messunsicherheit von Umgebungsbedingungen in Klimaprfkammern (IEC 60068-3-11:2007) This European Standard was approved by CENELEC on 2007-06-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate t
9、he 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 Central Secretariat or to any CENELEC member. This European Standard exis
10、ts 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 Central Secretariat has the same status as the official versions. CENELEC members are the national elect
11、rotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzer
12、land and the United Kingdom. EN 60068-3-11:2007 2 Foreword The text of document 104/409/FDIS, future edition 1 of IEC 60068-3-11, prepared by IEC TC 104, Environmental conditions, classification and methods of test, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 600
13、68-3-11 on 2007-06-01. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2008-03-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow
14、) 2010-06-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 60068-3-11:2007 was approved by CENELEC as a European Standard without any modification. _ 3 EN 60068-3-11:2007 CONTENTS INTRODUCTION.5 1 Scope 6 2 Normative references .6 3 Terms and def
15、initions .7 4 Concept of uncertainty10 4.1 Uncertainty, error and “true value” .10 4.2 Statements of uncertainty 11 4.3 Combining uncertainties 12 5 Tolerance.12 6 Humidity and temperature measurement .12 7 Methods for determining climatic test chamber uncertainties13 7.1 Empty chamber .15 7.2 Typic
16、al load.15 7.3 Measurement of conditions in the chamber during the test16 7.4 Conditions to measure .16 7.5 Measurements required .17 7.6 Sources of uncertainty .18 7.7 Essential contributions of uncertainty .19 8 Estimation of uncertainty components and their combination .23 9 Overall uncertainty o
17、f temperature measurement.23 9.1 General .23 9.2 Further considerations .25 10 Overall uncertainty of relative humidity measurement 25 10.1 Uncertainty of temperature measurement at each sensor point .26 10.2 Uncertainty of the relative humidity measurement.26 11 Anomalous data and presentation of r
18、esults 29 11.1 Average case analysis.29 11.2 Worst case analysis.29 Annex A (informative) Measurement data sets Loaded chamber.31 Annex ZA (normative) Normative references to international publications with their corresponding European publications34 Bibliography .33 EN 60068-3-11:2007 4 Figure 1 Ap
19、proaches to calibration method and uncertainty calculation .14 Figure 2 Illustration of the fluctuation of a temperature sensor 22 Table 1 Combination of temperature uncertainties 23 Table 2 Combination of temperature uncertainties at each point26 Table 3 Combination of humidity uncertainties27 Tabl
20、e A.1 Typical temperature measurement data set and its analysis and refs 31 Table A.2 Humidity measurements analysis based on Table A.1 temperatures 32 5 EN 60068-3-11:2007 INTRODUCTION This part of IEC 60068 provides guidance for analysing uncertainties of temperature and humidity in climatic test
21、chambers. It has been written for technicians, engineers and managers in environmental testing, and for anyone who needs to understand the results of environmental tests. The performance of climatic test chambers is a key concern in environmental test engineer-ing. To comply with any test specificat
22、ion, the performance of the chamber needs to be characterized to decide whether the generated conditions fall within the specified limits. This characterization can be a difficult task, and the analysis of uncertainties in chamber performance is often surrounded by confusion. This publication is int
23、ended to ease that process. In what follows, the concept of uncertainty of measurement is introduced first and then the significance of tolerance discussed. Aspects of humidity and temperature measurement are considered, followed by methods for determining and combining uncertainties. The cases of b
24、oth calibrating an empty chamber and of measuring conditions in a loaded chamber are considered. Finally, detailed guidance and worked examples are given for analysing results to give estimates of uncertainty in the measured performance. EN 60068-3-11:2007 6 ENVIRONMENTAL TESTING Part 3-11: Supporti
25、ng documentation and guidance Calculation of uncertainty of conditions in climatic test chambers 1 Scope This part of IEC 60068 demonstrates how to estimate the uncertainty of steady-state temperature and humidity conditions in temperature and humidity chambers. Since this is inextricably linked to
26、the methods of measurement, these are also described. This standard is equally applicable to all environmental enclosures, including rooms or laboratories. The methods used apply both to temperature chambers and combined temperature and humidity chambers. This standard is meant to help everyone usin
27、g climatic test chambers. Those already familiar with uncertainty of measurement will find it useful for guidance on typical sources of uncertainty and how they should be quantified and combined. It is also intended to assist the first-time or occasional user who has little or no knowledge of the su
28、bject. To discuss uncertainty, it is important first to understand what is being measured or characterized. The calibration or characterization of the performance of a chamber is concerned with the humidity and temperature of the air in the chamber, as experienced by the item under test, at a given
29、set point. This should not be confused with characterizing or calibrating the chamber sensor, which is a separate matter. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undate
30、d references, the latest edition of the referenced document (including any amendments) applies. IEC 60068-3-5: Environmental testing Part 3-5: Supporting documentation and guidance Confirmation of the performance of temperature chambers IEC 60068-3-6: Environmental testing Part 3-6: Supporting docum
31、entation and guidance Confirmation of the performance of temperature/humidity chambersISO 3534-1:2006, Statistics Vocabulary and symbols Part 1: General statistical terms and terms used in probability ISO 3534-2:2006, Statistics Vocabulary and symbols Part 2:Applied statisticsInternational Vocabular
32、y of basic and general standard terms in metrology. ISO, Geneva, Switzerland 1993 (ISBN 92-67-10175-1) VIM 7 EN 60068-3-11:2007 Guide to the expression of uncertainty in measurement. ISO, Geneva, Switzerland 1993. (ISBN 92-67-10188-9) GUM 3 Terms and definitions For the purposes of this document, th
33、e following terms and definitions apply. 3.1 calibration authority laboratory or other organization that performs calibrations and is itself accredited by the appropriate national accreditation body 3.2 climatic test chamber enclosure chamber or enclosed space where the internal temperature or tempe
34、rature and humidity can be controlled within specified limits 3.3 combined standard uncertainty standard uncertainty of the result of a measurement when that result is obtained from the values of a number of other quantities, equal to the positive square root of a sum of terms, the terms being the v
35、ariances or covariances of these other quantities weighted according to how the measurement result varies with changes in these quantities See also GUM. 3.4 correction value added algebraically to the result of a measurement to compensate determinable systematic error See also VIM. 3.5 confidence le
36、vel value of probability associated with a confidence interval NOTE The confidence level is the likelihood that the “true value” lies within the stated range of uncertainty usually expressed as a percentage, e.g. 95 %. See also ISO 3534-1. 3.6 coverage factor numerical factor to multiply the combine
37、d standard uncertainty to obtain an expanded uncertainty NOTE A coverage factor of k=2 corresponds to a confidence level of approximately 95 % if normally distributed and if the number of degrees of freedom is sufficiently large. See also GUM. EN 60068-3-11:2007 8 3.7 dew point temperature at which
38、the partial pressure of the water vapour is equal to the saturation vapour pressure over water or ice NOTE The temperature to which the air would have to cool (at constant pressure and constant water vapour content) in order to reach saturation. A state of saturation exists when the air is holding t
39、he maximum amount of water vapour possible at the existing temperature and pressure. 3.8 dispersion spread of repeated measurements of a quantity 3.9 drift change in the indication of a measuring system not related to a change in the quantity being measured See also VIM. NOTE The drift since the las
40、t calibration can be estimated and a correction applied to measured values. 3.10 error difference between result of a measurement and the true value 3.11 expanded uncertainty quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the dis
41、tribution of values that could reasonably be attributed to the measurand See also VIM. 3.12 fluctuation change (from the mean) in the temperature or humidity after stabilization from time to time at a point in space NOTE It may be measured by standard deviation or maximum deviation. 3.13 gradient ma
42、ximum difference in mean value, after stabilization, at any moment in time between two separate points in the working space 3.14 incident air conditioned airstream which flows into the working space 3.15 partial vapour pressure contribution of water vapour in a given volume of air at a constant pres
43、sure and temperature of the atmosphere 3.16 reference instrument previously calibrated instrument used to measure the conditions within the enclosure 9 EN 60068-3-11:2007 3.17 relative humidity ratio of actual partial vapour pressure to the saturation vapour pressure at any given temperature and pre
44、ssure, expressed as a percentage (% RH) 3.18 repeatability closeness of agreement between independent results obtained in the normal and correct operation of the same method on identical test material, in a short space of time, and under the same test conditions (such as the same operator, same appa
45、ratus, same laboratory) 3.19 resolution smallest changes between indications of the chamber controller display that can be meaningfully distinguished 3.20 saturation vapour pressure when a given volume of air, at a constant temperature, has water vapour present and is incapable of holding more water
46、 vapour it is said to be saturated 3.21 stabilization achievement of the state of temperature/humidity in the chamber when all mean values in the working space are constant and have maintained temperature/humidity within a given tolerance 3.22 standard deviation measure of the dispersion of a set of
47、 measurements NOTE The standard deviation, s, is the best estimate of sigma (the population standard deviation). See also GUM and/or VIM. 3.23 standard uncertainty uncertainty of the result of a measurement expressed as a standard deviation See also GUM. 3.24 tolerance acceptance limit specified or
48、chosen for a process or product See also ISO 3534-2. 3.25 traceability property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons, all having stated uncertain
49、ties NOTE The unbroken chain of comparisons is called a traceability chain. See also ISO 3534-1 and VIM. EN 60068-3-11:2007 10 3.26 true value value which characterizes a quantity, perfectly defined in the conditions which exist when that quantity is considered NOTE The true value of a quantity is a theoretical concept and, in general, cannot be known exactly but is estimated by measurement. See also ISO 3534-1. 3.27 uncertainty parameter, associated with the result of a measur
