ASTM E824-2010(2018)e1 6875 Standard Test Method for Transfer of Calibration From Reference to Field Radiometers.pdf

1、Designation: E824 10 (Reapproved 2018)1Standard Test Method forTransfer of Calibration From Reference to FieldRadiometers1This standard is issued under the fixed designation E824; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the

2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial changes made to subsections 4.4 and 10.1.1 and the organization of Section 8.INTRODUCTIONAccurate and prec

3、ise measurements of total solar and solar ultraviolet irradiance are required in: (1)the determination of the energy incident on surfaces and specimens during exposure outdoors tovarious climatic factors that characterize a test site, (2) the determination of solar irradiance andradiant exposure to

4、ascertain the energy available to solar collection devices such as flat-platecollectors, and (3) the assessment of the irradiance and radiant exposure in various wavelength bandsfor meteorological, climatic and earth energy-budget purposes. The solar components of principalinterest include total sol

5、ar radiant exposure (all wavelengths) and various ultraviolet components ofnatural sunlight that may be of interest, including both total and narrow-band ultraviolet radiantexposure.This test method for transferring calibration from reference to field instruments is only applicableto pyranometers an

6、d radiometers whose field angles closely approach 180 . instruments whichtherefore may be said to measure hemispherical radiation, or all radiation incident on a flat surface.Hemispherical radiation includes both the direct and sky (diffuse) geometrical components of sunlight,while global solar irra

7、diance refers only to hemispherical irradiance on a horizontal surface such thatthe field of view includes all of the hemispherical sky dome.For the purposes of this test method, the terms pyranometer and radiometer are used interchange-ably.1. Scope1.1 The method described in this standard applies

8、to thetransfer of calibration from reference to field radiometers to beused for measuring and monitoring outdoor radiant exposurelevels. This standard has been harmonized with ISO 9847.1.2 This test method is applicable to field radiometersregardless of the radiation receptor employed, but is limite

9、d toradiometers having approximately 180 (2 Steradian), fieldangles.1.3 The calibration covered by this test method employs theuse of natural sunshine as the source.1.4 Calibrations of field radiometers may be performed attilt as well as horizontal (at 0 from the horizontal to the earth).The essenti

10、al requirement is that the reference radiometer shallhave been calibrated at essentially the same tilt from horizontalas the tilt employed in the transfer of calibration.1.5 The primary reference instrument shall not be used as afield instrument and its exposure to sunlight shall be limited tocalibr

11、ation or intercomparisons.NOTE 1At a laboratory where calibrations are performed regularly itis advisable to maintain a group of two or three reference radiometers thatare included in every calibration. These serve as controls to detect anyinstability or irregularity in the standard reference instru

12、ment.1.6 Reference standard instruments shall be stored in amanner as to not degrade their calibration.1.7 The method of calibration specified for total solarpyranometers shall be traceable to the World RadiometricReference (WRR) through the calibration methods of thereference standard instruments (

13、Test Methods G167 and E816),and the method of calibration specified for narrow- andbroad-band ultraviolet radiometers shall be traceable to theNational Institute of Standards and Technology (NIST), orother internationally recognized national standards laboratories(Test Method G138).1This test method

14、 is under the jurisdiction of ASTM Committee G03 onWeathering and Durability and is the direct responsibility of Subcommittee G03.09on Radiometry.Current edition approved April 15, 2018. Published June 2018. Originallyapproved in 1994. Last previous edition approved in 2010 as E824 10. DOI:10.1520/E

15、0824-10R18E01.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelo

16、pment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.11.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this stand

17、ard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on

18、 Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E772 Terminology of Solar Energy ConversionE816 Test Method for Calibration of Pyrheliom

19、eters byComparison to Reference PyrheliometersG113 Terminology Relating to Natural and Artificial Weath-ering Tests of Nonmetallic MaterialsG138 Test Method for Calibration of a SpectroradiometerUsing a Standard Source of IrradianceG167 Test Method for Calibration of a Pyranometer Using aPyrheliomet

20、er2.2 Other Standard:ISO 9847 Solar EnergyCalibration of Field Pyranometersby Comparison to a Reference Pyranometer33. Terminology3.1 Definitions:3.1.1 See Terminologies E772 and G113 for terminologyrelating to this test method.4. Summary of Test Method4.1 Mount the reference radiometer, or pyranome

21、ter, and thefield (or test) radiometers, or pyranometers, on a commoncalibration table for horizontal calibration (Type A), on a tiltedplatform for calibration at tilt (Type B), or on an altazimuth orsun-pointing mount for normal-incidence calibration (Type C).Adjust the height of the photoreceptor,

22、 or radiation receptor, ofall instruments to a common elevation.4.2 Ensure that the pyranometers, or radiometers, azimuthreference marks point in a common direction.NOTE 2Current convention is to use the electrical connector as theazimuth reference and to point it towards the equator and downward. T

23、hereasons are (1) this convention diminishes the possibility of moistureintrusion into the connector, and (2) it ensures that instruments withdisparities in the hemispherical domes, or with domes not properlycentered over the receptor, are not operated in such a manner that theyamplify deviations fr

24、om the cosine law.4.3 For a transfer of calibration to a field instrument thatwill be used in a tilted position the following conditions mustbe met: The reference instrument must have a calibration at thedesired tilt angle; both instruments must be oriented at the tiltangle and facing the equator.4.

25、4 The analog voltage signal reading from each radiometeris measured, digitized, and stored using a calibrated data-acquisition instrument, or system.Aminimum of fifteen 10 minmeasurement sequences are obtained, each sequence compris-ing a minimum of 21 instantaneous readings. It is preferablethat a

26、larger number of measurement sequences be performedover several days duration and that data be taken in earlymorning or late afternoon, as well as near solar noon.NOTE 3Transfer of calibration to both total and narrow-band ultra-violet radiometers may require a larger number of measurement sequences

27、in order to account for spectral changes due to changing air mass bothearly and late in the day, and to the loss of north-sky ultraviolet whencalibrating at tilts.4.5 The data are mathematically ratioed, employing theinstrument constant of the reference instrument to determinethe instrument constant

28、 of the radiometer being calibrated. Themean value and the standard deviation are determined.5. Significance and Use5.1 The methods described represent the preferable meansfor calibration of field radiometers employing standard refer-ence radiometers. Other methods involve the employment ofan optica

29、l bench and essentially a point source of artificiallight. While these methods are useful for cosine and azimuthcorrection analyses, they suffer from foreground view factorand directionality problems. Transfer of calibration indoorsusing artificial sources is not covered by this test method.5.2 Trac

30、eability of calibration of global pyranometers isaccomplished when employing the method using a referenceglobal pyranometer that has been calibrated, and is traceable tothe World Radiometric Reference (WRR). For the purposes ofthis test method, traceability shall have been established if aparent ins

31、trument in the calibration chain participated in anInternational Pyrheliometric Comparison (IPC) conducted atthe World Radiation Center (WRC) in Davos, Switzerland.Traceability of calibration of narrow- and broad-band radiom-eters is accomplished when employing the method using areference ultraviole

32、t radiometer that has been calibrated and istraceable to the National Institute of Standards and Technology(NIST), or other national standards organizations. See Zerlaut4for a discussion of the WRR, the IPCs and their results.5.2.1 The reference global pyranometer (for example, onemeasuring hemisphe

33、rical solar radiation at all wavelengths)shall have been calibrated by the shading-disk or componentsummation method against one of the following instruments:5.2.1.1 An absolute cavity pyrheliometer that participated ina WMO sanctioned IPCs (and therefore possesses a WRRreduction factor),5.2.1.2 An

34、absolute cavity radiometer that has been inter-compared (in a local or regional comparison) with an absolutecavity pyrheliometer meeting the requirements given in5.2.1.1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annu

35、al Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Zerlaut, G. A., “Solar Radiation Instrumentation,” Chapter 5 in

36、 SolarResources, The MIT Press, Cambridge, MA, 1989, pp. 173308.E824 10 (2018)125.2.1.3 A WMO First Class pyrheliometer that was cali-brated by direct transfer from such an absolute cavity.5.2.2 Alternatively, the reference pyranometer may havebeen calibrated by direct transfer from a World Meteorol

37、ogicalOrganization (WMO) First Class pyranometer that was cali-brated by the shading-disk method against an absolute cavitypyrheliometer possessing a WRR reduction factor, or by directtransfer from a WMO Standard Pyranometer (see WMOsGuide WMONo. 85for a discussion of the classification ofsolar radi

38、ometers).NOTE 4Any of the absolute radiometers participating in the aboveintercomparisons and being within 60.5 % of the mean of all similarinstruments compared in any of those intercomparisons, shall be consid-ered suitable as the primary reference instrument.5.2.3 The reference ultraviolet radiome

39、ter, regardless ofwhether it measures total ultraviolet solar radiation, or narrow-band UV-A or UV-B radiation, or a defined narrow bandsegment of ultraviolet radiation, shall have been calibrated byone of the following:5.2.3.1 By comparison to a standard source of spectralirradiance that is traceab

40、le to NIST or to the appropriatenational standards organizations of other countries (usingappropriate filter correction factors),65.2.3.2 By comparison to the integrated spectral irradiancein the appropriate wavelength band of a spectroradiometer thathas itself been calibrated against such a standar

41、d source ofspectral irradiance, and5.2.3.3 By comparison to a spectroradiometer that hasparticipated in a regional or national Intercomparison ofSpectroradiometers, the results of which are of referencequality.NOTE 5The calibration of reference ultraviolet radiometers using aspectroradiometer, or by

42、 direct calibration against standard sources ofspectral irradiance (for example, deuterium or 1000 W tungsten-halogenlamps) is the subject of Test Method G138.5.3 The calibration method employed assumes that theaccuracy of the values obtained are independent of time of yearwithin the constraints imp

43、osed by the test instruments tem-perature compensation (neglecting cosine errors). The methodpermits the determination of possible tilt effects on the sensi-tivity of the test instruments light receptor.5.4 The principal advantage of outdoor calibration of radi-ometers is that all types of radiomete

44、rs are related to a singlereference under realistic irradiance conditions.5.5 The principal disadvantages of the outdoor calibrationmethod are the time required and the fact that the naturalenvironment is not subject to control (but the calibrationstherefore include all of the instrumental character

45、istics of boththe reference and test radiometers that are influenced simulta-neously by the environment). Environmental circumstancessuch as ground reflectance or shading, or both, must beminimized and affect both instruments similarly.5.6 The reference radiometer must be of the same type asthe test

46、 radiometer, since any difference in spectral sensitivitybetween instruments will result in erroneous calibrations. Thereader is referred to ISO TR 96737and ISO TR 99018fordiscussions of the types of instruments available and their use.6. Interferences6.1 In order to minimize systematic errors the r

47、eference andtest radiometers must be as nearly alike in all respects aspossible.6.1.1 The spectral response of both the reference and testradiometers must be as nearly identical as possible.6.2 Sky ConditionsThe measurements selected in deter-mining the instrument constant shall be for periods of es

48、sen-tially uniform rates of change of radiation (either cloudless orovercast conditions). Periods selected shall be for 10 to 20 minsegments. Measurements selected under varying cloudy con-ditions may result in erroneous calibrations if the reference andtest radiometers possess significantly differe

49、nt response times(see also 5.6).7. Apparatus7.1 Data Acquisition InstrumentA digital voltmeter ordata logger capable of repeatability to 0.1 % of averagereading, and an uncertainty of 60.2 % with an input imped-ance of at least 1 M may be employed. Data loggers havingprintout must be capable of a measurement frequency of atleast two per minute. A data logger having three-channelcapacity may be useful.7.2 Fixed-Angle Calibration TableA precision calibrationtable required for all horizontal and fixed angle tilt tests that islevel at 0 horizontal and that i