1、February 2008DEUTSCHE NORM English price group 19No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 17.120.20!$L)V“141065
2、1www.din.deDDIN EN ISO 748Hydrometry Measurement of liquid flow in open channels using current-meters orfloats (ISO 748:2007)English version of DIN EN ISO 748:2008-02Hydrometrie Durchflussmessung in offenen Gerinnen mittels Fliegeschwindigkeitsmessgerten oderSchwimmern (ISO 748:2007)Englische Fassun
3、g DIN EN ISO 748:2008-02SupersedesDIN EN ISO 748:2000-03www.beuth.deDocument comprises 52 pagesDIN EN ISO 748:2008-02 2 National foreword This standard has been prepared by Technical Committee CEN/TC 318 “Hydrometry” (Secretariat: BSI, United Kingdom). The responsible German body involved in its pre
4、paration was the Normenausschuss Wasserwesen (Water Practice Standards Committee), Technical Committee NA 119-06-10 AA Hydrometrie. National standards organizations are bound to implement this European Standard without any modification. The DIN Standards corresponding to the International Standards
5、referred to in the EN are as follows: ISO 772 DIN EN ISO 772 ISO 4375 DIN EN ISO 4375 Amendments This standard differs from DIN EN ISO 748:2000-03 as follows: a) The methods of calculation and evaluation used to determine the velocity have been revised. b) New parameters and equations have been spec
6、ified for the determination of uncertainties in measurement. c) More examples of measuring methods are given in the annexes. Previous editions DIN EN ISO 748: 2000-03 National Annex NA (informative) Bibliography DIN EN ISO 772, Hydrometric determinations Vocabulary and symbols DIN EN ISO 4375, Hydro
7、metric determinations Cableway systems for stream gauging EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 748October 2007ICS 17.120.20 Supersedes EN ISO 748:2000 English VersionHydrometry - Measurement of liquid flow in open channels usingcurrent-meters or floats (ISO 748:2007)Hydromtrie - Mes
8、urage du dbit des liquides dans lescanaux dcouverts au moyen de dbitmtres ou deflotteurs (ISO 748:2007)Hydrometrie - Durchflussmessung in offenen Gerinnenmittels Fliegeschwindigkeitsmessgerten oderSchwimmern (ISO 748:2007)This European Standard was approved by CEN on 21 September 2007.CEN members ar
9、e bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to th
10、e CEN 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same st
11、atus as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania,
12、Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwid
13、e for CEN national Members.Ref. No. EN ISO 748:2007: E2 EN ISO 748:2007 (E) Contents Page Foreword .4 1 Scope .5 2 Normative references .5 3 Terms and definitions 5 4 Principle of the methods of measurements .5 5 Selection and demarcation of site 6 5.1 Selection of site 6 5.2 Demarcation of site 7 6
14、 Measurement of cross-sectional area 7 6.1 General .7 6.2 Measurement of width 7 6.3 Measurement of depth .8 7 Measurement of velocity 9 7.1 Measurement of velocity using current-meters .9 7.1.1 Rotating-element current-meters 9 7.1.2 Electromagnetic current-meters .9 7.1.3 Measurement procedure 9 7
15、.1.4 Oblique flow . 10 7.1.5 Determination of the mean velocity in a vertical 11 7.1.6 Errors and limitations 14 7.2 Measurement of velocity using floats . 15 7.2.1 General 15 7.2.2 Selection of site . 15 7.2.3 Measuring procedure 15 7.2.4 Types of float 15 7.2.5 Determination of velocity 16 7.2.6 M
16、ain sources of error 17 8 Computation of discharge 17 8.1 General 17 8.2 Graphical method 17 8.2.1 Depth-velocity-integration 17 8.2.2 Velocity-area Integration method (velocity-contour method) . 18 8.3 Arithmetic methods . 20 8.3.1 Mean-section method 20 8.3.2 Mid-section method . 20 8.4 Independen
17、t vertical method 21 8.5 Mean-section method Horizontal planes 24 8.6 Determination of discharge from surface-float velocity measurements . 24 8.7 Determination of discharge for variations of water level 26 8.7.1 General 26 8.7.2 Computation of discharge 26 8.7.3 Computation of mean water level 26 9
18、 Uncertainties in flow measurement . 27 9.1 General 27 9.2 Definition of uncertainty . 27 9.3 Method of calculating the uncertainty in discharge by measurement of velocity by current-meter . 28 9.3.1 General 28 DIN EN ISO 748:2008-02 3 EN ISO 748:2007 (E) 9.3.2 Contributory uncertainties 28 9.3.3 Ex
19、ample .30 9.3.4 Combined uncertainty 30 9.4 Method of calculating the uncertainty in discharge by measurement of velocity using floats 31 9.4.1 General 31 9.4.2 Contributory uncertainties 31 9.4.3 Combined uncertainty in discharge .32 9.4.4 Example .32 Annex A (informative) Correction for sag, pull,
20、 slope and temperature in measurement of cross-section width by tape or wire 34 Annex B (informative) Distance measurement across the cross-section .37 Annex C (informative) Corrections for wetted length of wire when measuring depths with wire not normal to surface .40 Annex D (informative) Correcti
21、on for drift .43 Annex E (informative) Uncertainties in the velocity-area measurement 44 Annex F (informative) Determination of mean velocity from float measurements .48 Bibliography .50 DIN EN ISO 748:2008-02 Foreword 4 This document (EN ISO 748:2007) has been prepared by Technical Committee ISO/TC
22、 113 “Hydrometric determinations“ in collaboration with Technical Committee CEN/TC 318 “Hydrometry” the secretariat of which is held by BSI. 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 April 2
23、008, and conflicting national standards shall be withdrawn at the latest by April 2008. This document supersedes EN ISO 748:2000. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria,
24、 Belgium, Bulgaria, 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 n
25、otice The text of ISO 748:2007 has been approved by CEN as a EN ISO 748:2007 without any modification. EN ISO 748:2007 (E) DIN EN ISO 748:2008-02 1 Scope This International Standard specifies methods for determining the velocity and cross-sectional area of water flowing in open channels without ice
26、cover, and for computing the discharge therefrom. It covers methods of employing current-meters or floats to measure the velocities. It should be noted that although, in some cases, these measurements are intended to determine the stage-discharge relation of a gauging station, this International Sta
27、ndard deals only with single measurements of the discharge; the continuous recording of discharges over a period of time is covered in ISO 1100-1 and ISO 1100-2. NOTE The methods for determining the velocity and cross-sectional area of water flowing in open channels with ice cover are specified in I
28、SO 9196. 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 772, Hydromet
29、ric determinations Vocabulary and symbols ISO 1088, Hydrometry Velocity-area methods using current-meters Collection and processing of data for determination of uncertainties in flow measurement ISO 2537, Hydrometry Rotating-element current-meters ISO 3455, Hydrometry Calibration of current-meters i
30、n straight open tanks ISO/TS 15768, Measurement of liquid velocity in open channels Design, selection and use of electromagnetic current meters 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 772 apply. 4 Principle of the methods of measurements 4.1
31、The principle of these methods consists of determining velocity and cross-sectional area. A measuring site is chosen conforming to the specified requirements (see Clause 5); the width, depending on its magnitude, is measured either by means of steel tape or by some other surveying method, and the de
32、pth is measured at a number of points (known as verticals) across the width, sufficient to determine the shape and area of the cross-section (see Clause 6). 5 EN ISO 748:2007 (E) DIN EN ISO 748:2008-02 Velocity observations using current-meters are made at each vertical preferably at the same time a
33、s measurement of depth, especially in the case of unstable beds (see 7.1.5). Velocity observations can also be made using surface floats or velocity-rods (see 7.2). 4.2 The discharge is computed either arithmetically or graphically by summing the products of the velocity and corresponding area for a
34、 series of observations in a cross-section. If unit width discharge is required, it is generally computed from the individual observations at each measurement vertical. 5 Selection and demarcation of site 5.1 Selection of site The site selected should comply as far as possible with the following req
35、uirements. a) The channel at the measuring site should be straight and of uniform cross-section and slope in order to minimize abnormal velocity distribution. When the length of the channel is restricted, it is recommended for current-meter measurements that the straight length upstream should be at
36、 least twice that downstream. b) Flow directions for all points on any vertical across the width should be parallel to one another and at right angles to the measurement section. c) The bed and margins of the channels should be stable and well defined at all stages of flow in order to facilitate acc
37、urate measurement of the cross-section and ensure uniformity of conditions during and between discharge measurements. d) The curves of the distribution of velocities should be regular in the vertical and horizontal planes of measurement. e) Conditions at the section and in its vicinity should also b
38、e such as to preclude changes taking place in the velocity distribution during the period of measurement. f) Sites displaying vortices, reverse flow or dead water should be avoided. g) The measurement section should be clearly visible across its width and unobstructed by trees, aquatic growth or oth
39、er obstacles. h) Measurement of flow from bridges can be a convenient and sometimes safer way of sampling width, depth and velocity. When gauging from a bridge with divide piers, each section of the channel should be measured separately. Particular care should be taken in determining the velocity di
40、stribution when bridge apertures are surcharged or obstructed. i) The depth of water at the section should be sufficient at all stages to provide for the effective immersion of the current-meter or float, whichever is to be used. j) If the site is to be established as a permanent station, it should
41、be easily accessible at all times with all necessary measurement equipment. k) The section should be sited away from pumps, sluices and outfalls, if their operation during a measurement is likely to create unsteady flow conditions. l) Sites where there is converging or diverging flow should be avoid
42、ed. m) In those instances where it is necessary to make measurements in the vicinity of a bridge, it is preferable that the measuring site be upstream of the bridge. However, in certain cases and where accumulation of ice, logs or debris is liable to occur, it is acceptable that the measuring site b
43、e downstream of the bridge. 6 EN ISO 748:2007 (E) DIN EN ISO 748:2008-02 n) The measurement of flow under ice cover is dealt with in ISO 9196. For streams subject to formation of ice cover, the requirements of measurement specified in this International Standard can be used during the free water sea
44、son. o) It may, under certain conditions of river flow or level, prove necessary to carry out current-meter measurements on sections other than the original chosen location. This is quite acceptable if there are no substantial unmeasured losses or gains to the river in the intervening reach and so l
45、ong as all flow measurements can be related to any stage value recorded at the principal reference section. 5.2 Demarcation of site 5.2.1 If the site is to be established as a permanent station or likely to be used frequently for future measurement, it should be provided with means for demarcation o
46、f the cross-section and for determination of stage. Where the site is used only once, or infrequently, and there are no means of determining stage values on site, care should be taken to ensure that the water level and/or flow do not change significantly during the measurement period. 5.2.2 The posi
47、tion of each cross-section, normal to the mean direction of flow, shall be defined on the two banks by clearly visible and readily identifiable markers. Where a site is subject to considerable snow cover, the section line-markers may be referenced to other objects such as rock cairns. 5.2.3 The stag
48、e shall be read from a gauge at intervals throughout the period of measurement and the gauge datum shall be related by precise levelling to a standard datum. 5.2.4 An auxiliary gauge on the opposite bank shall be installed where there is likelihood of a difference in the level of water surface betwe
49、en the two banks. This is particularly important in the case of very wide rivers. The mean of the measurements taken from the two gauges shall be used as the mean level of the water surface and as a base for the cross-sectional profile of the stream. 6 Measurement of cross-sectional area 6.1 General The cross-sectional profile of the open channel at the gauging-site shall be determined at a sufficient number of points to establish the shape of the bed. The location of each point is determined by measuring its horizontal distance to a fixed reference p
