1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Collection and processing of data for determination of uncertainties in flow measurementICS 17.120.
2、20Hydrometry Velocity-area methods using current-meters BRITISH STANDARDBS ISO 1088:2007BS ISO 1088:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2007 BSI 2007ISBN 978 0 580 55460 5Amendments issued since publicationAmd. No. Dat
3、e CommentsThis 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 legal obligations.National forewordThis British Standard is the UK implementation of ISO
4、 1088:2007. It supersedes BS 3680-3F:1986*ISO 1088:1985 which is withdrawn.The UK participation in its preparation was entrusted by Technical Committee CPI/113, Hydrometry, to Subcommittee CPI/113/5, Measuring instruments and equipment.A list of organizations represented on this committee can be obt
5、ained on request to its secretary.Reference numberISO 1088:2007(E)INTERNATIONAL STANDARD ISO1088Third edition2007-07-01Hydrometry Velocity-area methods using current-meters Collection and processing of data for determination of uncertainties in flow measurement Hydromtrie Mthodes dexploration du cha
6、mp des vitesses laide de moulinets Recueil et traitement des donnes pour la dtermination des incertitudes de mesurage du dbit BS ISO 1088:2007ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Symbols and abbreviated terms . 2 4 Types of errors and procedure for
7、estimating the uncertainties in flow measurement 3 4.1 Principle. 3 4.2 Occurrence of error 4 4.3 Sources of error 5 4.4 Determination of the individual components of the uncertainty . 6 4.5 Total uncertainty in discharge. 7 5 Collection and processing of data for the investigation of component unce
8、rtainties type A evaluation of uncertainties. 8 5.1 Data on the local point velocity. 8 5.2 Data on the average velocity . 9 5.3 Data on the velocity-area method . 10 5.4 Integration method . 11 5.5 Calibration curves. 11 5.6 Distance measurements 11 5.7 Depth measurements . 12 6 Data processing 12
9、6.1 General. 12 6.2 Error-type i. 13 6.3 Error-type ii Approximation of mean velocity in the vertical. 15 6.4 Error-type iii Limited number of verticals17 Annex A (informative) Characteristics of rivers from which data were collected . 21 Annex B (normative) Effect of increasing measuring time on un
10、certainty 26 Annex C (normative) Local point velocity measurements - Report form. 27 Annex D (normative) Average velocity measurements Report form . 31 Annex E (normative) Velocity-area method Report form 34 Annex F (informative) Examination of Error Types i, ii, and iii 38 Annex G (informative) Unc
11、ertainties in velocity-area measurement components 41 Annex H (informative) Calculation of the uncertainty in a current-meter gauging 45 Bibliography . 48 BS ISO 1088:2007iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
12、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
13、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
14、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
15、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 1088 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommitt
16、ee SC 5, Instruments, equipment and data management. This third edition cancels and replaces the second edition (ISO 1088:1985), which has been revised to incorporate ISO/TR 7178 (based on ISO/DATA No. 2) and edited in accordance with ISO/IEC Guide 98:1995, Guide to the expression of uncertainty in
17、measurement (GUM). This third edition of ISO 1088 also cancels and replaces ISO/TR 7178, all provisions of which have been incorporated into this edition. BS ISO 1088:2007vIntroduction All measurements of physical quantities are subject to uncertainties, which can be due to biases (systematic errors
18、) introduced in the manufacture, calibration, and maintenance of measurement instruments, or to random scatter caused by a lack of sensitivity of the instruments, and to other sources of error. During the preparation of the first edition of ISO 748, much discussion was given to the question of the m
19、agnitude of errors in measurements, and it was concluded that recommendations could only be formulated on the basis of an analysis of sufficient data. Moreover, it was recognized that to be able to analyze such data statistically, it was essential that the data be collected and recorded on a standar
20、dized basis and in a systematic manner, and this recognition led to the preparation of ISO 1088 and ISO/TR 7178. On the basis of the procedures given in the first editions of ISO 748 (1968) and ISO 1088 (1973), data were subsequently collected and processed from the following rivers (see Annex A for
21、 the characteristics of these rivers) and ISO/TR 7178 was accordingly published: a) Rivers Ganga, Jalangi, Yamuna, and Visvesvaraya Canal, in India; b) River IJssel, in the Netherlands; c) Rivers Derwent, Eden, Lambourne, Ouse, Tyne, and Usk in the United Kingdom; d) Rivers Columbia and Mississippi,
22、 in the United States. Further data obtained on the Rivers Ganga and Krishna, in India, and the Spey,Tay, Tweed, Tyne, Gala Water, Yarrow Water, Ettrick Water, and the Clyde, in the United Kingdom, were received later, but could not be included in the processing. The procedures for estimating the co
23、mponent uncertainties and the uncertainty in discharge in this International Standard conform to the ISO/IEC Guide 98, Guide to the expression of uncertainty in measurement (GUM). BS ISO 1088:2007blank1Hydrometry Velocity-area methods using current-meters Collection and processing of data for determ
24、ination of uncertainties in flow measurement 1 Scope This International Standard provides a standard basis for the collection and processing of data for the determination of the uncertainties in measurements of discharge in open channels by velocity-area methods using current-meters. To determine th
25、e discharge in open channels by the velocity-area method, components of the flow (velocity, depth and breadth) need to be measured. The component measurements are combined to compute the total discharge. The total uncertainty in the computed discharge is a combination of the uncertainties in the mea
26、sured components. Clause 4 of this International Standard deals with the types of errors and uncertainties involved. Clauses 5 and 6 present a standard procedure to estimate the component uncertainties by the collection and processing of the necessary data. This International Standard is intended to
27、 be applied to velocity-area methods that involve measurement of point velocities at a relatively small number of discrete depths and transverse positions in the flow cross-section, as described in ISO 748. This International Standard is not intended to be applied to measurements made by Acoustic Do
28、ppler Velocity Profilers (ADVP) or other instruments that produce essentially continuous velocity profiles of the flow field. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For un
29、dated references, the latest edition of the referenced document (including any amendments) applies. ISO 748, Measurement of liquid flow in open channels Velocity-area methods ISO 4363, Measurement of liquid flow in open channels Methods for measurement of characteristics of suspended sediment ISO 43
30、64, Measurement of liquid flow in open channels Bed material sampling BS ISO 1088:20072 3 Symbols and abbreviated terms a coefficient of linear regression, slope of trend line bibreadth (width) of segment i didepth at vertical in segment i L number of sets of measurements (error type ii) J number of
31、 measurements per set (error types ii and iii) k time displacement in autocorrelation function (of time interval, etc.) k coverage factor for expanded uncertainty (taken as 2, corresponding to a level of confidence of approximately 95 %) m number of verticals or sections per measurement cross-sectio
32、n n multiple of basic exposure-time for velocity measurement (error type i) ninumber of depths in vertical i at which velocity measurements are made Q discharge Qjdischarge of measurement j in a set of measurements (error type iii) Srelstandard deviation of the relative mean velocities (error type i
33、i) SFmean standard deviation of all measurement sets together due to velocity fluctuations (error type ii) SF,istandard deviation of sampling error in measurement set i (error type ii) Ssstandard deviation of the sampling error due to the computation rule (error type ii) Sistochastic sampling error
34、of mean velocity in vertical i (error type ii) ,viS unobservable random sampling error of mean velocity in vertical i (error type ii) Ss,hd(m) standard deviation of relative error when m verticals are applied (error type iii) tiinstant of time of observation i (error type i) t0initial measuring time
35、 (basic time interval) t mean of observation times tiin a linear trend segment (error type i) uistandard relative (percentage) uncertainty in uncertainty component i u standard relative (percentage) combined uncertainty of measurement U expanded relative (percentage) uncertainty with coverage factor
36、 k ucstandard relative (percentage) uncertainty due to responsiveness of current-meter ubstandard relative (percentage) uncertainty in width measurement udstandard relative (percentage) uncertainty in depth measurement BS ISO 1088:20073uestandard relative (percentage) uncertainty due to velocity flu
37、ctuations umstandard relative (percentage) uncertainty due to limited number of verticals upstandard relative (percentage) uncertainty due to limited number of depths at which velocity is measured usstandard relative (percentage) uncertainty due to instrument calibration errors vivelocity at time ti
38、or in vertical i Viactual velocity at time tior in vertical i iv corrected velocity from which trend has been removed (error type i) ()vt trend-line velocity (error type i) iv mean velocity in vertical i or at point i; relV mean of the relative mean velocities (error type ii) rel, jV mean relative v
39、elocity in the jthprofile (error type ii) s mean sampling error for the entire series of measurement sets (error type ii) s,i mean sampling error in measurement set i (error type ii) ()m mean relative error when m verticals are applied (error type iii) Fstandard deviation of velocity fluctuations (e
40、rror type i) Additional symbols are defined in the text. Due to the statistical nature of this International Standard, it is necessary to have symbols representing observed values and true values of variables. The symbols therefore might not conform to ISO 772. 4 Types of errors and procedure for es
41、timating the uncertainties in flow measurement 4.1 Principle The principle of the velocity-area method consists in determining from measurements the distribution of the flow velocity in the cross-section and the area of the cross-section, and using these observations for the computation of the disch
42、arge. The measurements of the velocity are made in a number of verticals. In each vertical the mean velocity is determined from measurements at a selected number of points. The discharge per unit width can be found by multiplying the mean velocity by the depth in the vertical considered. Each vertic
43、al is assumed to be representative of a segment of the cross-sectional area. The selection of the number and location of the verticals determines the width of these segments. Recommendations on the number of verticals required are given in 4.4.3 c). Assuming that the discharge has remained constant
44、during the measurements, summation of the discharge in the various segments gives the total discharge through the section. BS ISO 1088:20074 4.2 Occurrence of error In general, the result of a measurement is only an estimate of the true value of the quantity subjected to measurement. The discrepancy
45、 between the true and measured values is the measurement error. The measurement error, which cannot be known, causes an uncertainty about the correctness of the measurement result. The measurement error is a combination of component errors, which arise during the performance of various elementary op
46、erations during the measurement process. For measurements of composite quantities, which depend on several component quantities, the total error of the measurement is a combination of the errors in all component quantities. Determination of measurement uncertainty involves identification and charact
47、erization of all components of error, and the quantification and combination of the corresponding uncertainties. ISO/IEC Guide 98 treats measurement uncertainty using concepts and formulas for probability distributions, expected values, standard deviations, and correlations of random variables. The
48、standard deviation of the measurement error is taken as the quantitative measure of uncertainty. ISO/IEC Guide 98 does not make use of the traditional categorization of errors as random and systematic. That categorization can be difficult to apply in practice. For example, an error that is systemati
49、c in one measurement process might become random in a different process. The essential characteristic of systematic errors is that they are not reduced by averaging of replicate measurements. The guide makes it clear that accurate description of the measurement process and correct mathematical formulation of the uncertainty equations are sufficient to account for the fact that some uncertainty sources are not reduced by averaging of replicate measurements whereas others are reduced, without reliance on th
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