BS-ISO-17714-2007.pdf
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1、BRITISH STANDARD BS ISO 17714:2007 Meteorology Air temperature measurements Test methods for comparing the performance of thermometer shields/screens and defining important characteristics ICS 07.060 ? Licensed Copy: London South Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT
2、+00:00 2007, Uncontrolled Copy, (c) BSI BS ISO 17714:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2007 BSI 2007 ISBN 978 0 580 54322 7 National foreword This British Standard is the UK implementation of ISO 17714:2007. The UK
3、participation in its preparation was entrusted to Technical Committee EH/2, Air quality. A 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 f
4、or its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments Licensed Copy: London South Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT+00:00 2007, Uncontrolled Copy, (c
5、) BSI Reference number ISO 17714:2007(E) INTERNATIONAL STANDARD ISO 17714 First edition 2007-07-01 Meteorology Air temperature measurements Test methods for comparing the performance of thermometer shields/screens and defining important characteristics Mtorologie Mesurage de la temprature de lair Mt
6、hodes dessai pour comparer les performances dabris/dcrans pour thermomtres et dfinir les caractristiques importantes BS ISO 17714:2007 Licensed Copy: London South Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT+00:00 2007, Uncontrolled Copy, (c) BSI ii Licensed Copy: London So
7、uth Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT+00:00 2007, Uncontrolled Copy, (c) BSI iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Terms and definitions. 1 3 Field test conditions. 2 3.1 Field test site. 2 3.2 Respective location of screens. 2 3.3 Screens 3
8、3.4 Thermometers. 3 3.5 Additional meteorological variables. 3 3.6 Data sampling . 4 3.7 Reference values 4 3.8 Quality control. 4 3.9 Long-term intercomparison. 5 3.10 Typical conditions 5 3.11 Documentation 6 4 Field test methods 6 4.1 Comparability analysis. 6 4.2 Global analysis of air temperatu
9、re 6 4.3 Analysis of extreme values 6 4.4 Statistical analysis of radiation error 7 4.5 Influence of surface albedo . 7 4.6 Selection of typical conditions 7 5 Measurement of screen characteristics. 8 5.1 Aspiration rate. 8 5.2 Internal ventilation factor. 8 5.3 Representative height and screen refe
10、rence point. 8 5.4 System response time 8 Annex A (informative) Influence factors 10 Annex B (informative) Examples of useful test-report graphs 13 Bibliography. 18 BS ISO 17714:2007 Licensed Copy: London South Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT+00:00 2007, Uncont
11、rolled Copy, (c) BSI iv Foreword ISO (the International Organization 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
12、 a subject for which a technical committee has been established 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 Commiss
13、ion (IEC) on all matters of electrotechnical standardization. International 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
14、committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies 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
15、not be held responsible for identifying any or all such patent rights. ISO 17714 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 5, Meteorology. BS ISO 17714:2007 Licensed Copy: London South Bank University, London South Bank University, Wed Aug 08 03:51:12 GMT+00:00 200
16、7, Uncontrolled Copy, (c) BSI v Introduction Commonly used air temperature sensors require protection from influences such as solar and terrestrial radiation, rain and snow. Screens (also known as shields) protect the thermometers from these influences. At present, there is no commonly accepted refe
17、rence screen design, nor are there generally accepted test methods to determine performance characteristics of screens. Screens that protect the temperature sensors from daytime heating and nighttime cooling due to radiation transfer are necessary for proper air temperature measurements. In very gen
18、eral terms, a poor design of the screen will tend to give higher daytime and lower nighttime temperatures. This International Standard was developed to define the most relevant screen characteristics and to provide the methods to determine or compare screen performances. Air temperature is a basic m
19、eteorological variable. Temperature sensors are widely used in all human activities and are well known and controlled. For the measurement of the outside air temperature, the sensor must be protected against external influence, mainly radiation and hydrometeors (e.g. precipitation, fog). The sensor
20、is usually protected by a screen, but even then, measurement errors of up to 5 K may be encountered. The general function of a screen for operational temperature measurements used in meteorological applications is given in WMO No. 8 3. The following text is an extract from this document. “Radiation
21、from the sun, clouds, the ground and other surrounding objects passes through the air without appreciably changing its temperature, but a thermometer exposed freely in the open can absorb considerable radiation. As a consequence, its temperature may differ from the true air temperature, the differen
22、ce depending on the radiation intensity and on the ratio of absorbed radiation to dissipated heat. For some thermometer elements such as the very fine wire used in an open-wire resistance thermometer, the difference may be very small or even negligible, but with the more usual operational thermomete
23、rs the temperature difference may reach 25 K under extremely unfavourable conditions. Therefore, in order to ensure that the thermometer is at true air temperature it is necessary to protect the thermometer from radiation by a screen or shield which also serves to support the thermometer. This scree
24、n also shelters it from precipitation while allowing the free circulation of air around it, and prevents accidental damage. Maintaining a free circulation may, however, be difficult to achieve under conditions of rime ice accretion. Practices for reducing observation errors under such conditions wil
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