1、Designation: E824 10Standard 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 year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONAccurate and precise measurements of total solar and solar ultraviolet irradiance are required in: (1)the determination of the e
3、nergy 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 ascertain the energy available to solar collection devices such as flat-platecollectors, and (3) the assessment
4、 of the irradiance and radiant exposure in various wavelength bandsfor meteorological, climatic and earth energy-budget purposes. The solar components of principalinterest include total solar radiant exposure (all wavelengths) and various ultraviolet components ofnatural sunlight that may be of inte
5、rest, including both total and narrow-band ultraviolet radiantexposure.This test method for transferring calibration from reference to field instruments is only applicableto pyranometers and radiometers whose field angles closely approach 180 . instruments whichtherefore may be said to measure hemis
6、pherical 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 irradiance refers only to hemispherical irradiance on a horizontal surface such thatthe field of view includes all
7、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 to thetransfer of calibration from reference to field radiometers to beused for measuring and monitoring outdoo
8、r 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 limited toradiometers having approximately 180 (2p Steradian), fieldangles.1.3 The calibration covered by this test m
9、ethod 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 essential requirement is that the reference radiometer shallhave been calibrated at essentially the same tilt from ho
10、rizontalas 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 tocalibration or intercomparisons.NOTE 1At a laboratory where calibrations are performed regularly itis advisable to m
11、aintain 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 instrument.1.6 Reference standard instruments shall be stored in amanner as to not degrade their calibration.1.7 The
12、 method of calibration specified for total solarpyranometers shall be traceable to the World RadiometricReference (WRR) through the calibration methods of thereference standard instruments (Test Methods G167 and E816),and the method of calibration specified for narrow- andbroad-band ultraviolet radi
13、ometers shall be traceable to theNational Institute of Standards and Technology (NIST), orother internationally recognized national standards laboratories(Test Method G138).1This test method is under the jurisdiction of ASTM Committee G03 onWeathering and Durability and is the direct responsibility
14、of Subcommittee G03.09on Radiometry.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1994. Last previous edition approved in 2005 as E824 05. DOI:10.1520/E0824-10.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
15、 United States.1.8 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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
16、2. Referenced Documents2.1 ASTM Standards:2E772 Terminology Relating to Solar Energy ConversionE816 Test Method for Calibration of Pyrheliometers byComparison to Reference PyrheliometersG113 Terminology Relating to Natural andArtificial Weath-ering Tests of Nonmetallic MaterialsG138 Test Method for
17、Calibration of a SpectroradiometerUsing a Standard Source of IrradianceG167 Test Method for Calibration of a Pyranometer Usinga Pyrheliometer2.2 Other Standard:ISO 9847 Solar EnergyCalibration of Field Pyranometersby Comparison to a Reference Pyranometer33. Terminology3.1 Definitions:3.1.1 See Termi
18、nologies E772 and G113 for terminologyrelating to this test method.4. Summary of Test Method4.1 Mount the reference radiometer, or pyranometer, and thefield (or test) radiometers, or pyranometers, on a commoncalibration table for horizontal calibration (Type A), on a tiltedplatform for calibration a
19、t tilt (Type B), or on an altazimuth orsun-pointing mount for normal-incidence calibration (Type C).Adjust the height of the photoreceptor, or radiation receptor, ofall instruments to a common elevation.4.2 Ensure that the pyranometers, or radiometers, azimuthreference marks point in a common direct
20、ion.NOTE 2Current convention is to use the electrical connector as theazimuth reference and to point it towards the equator and downward. Thereasons are (1) this convention diminishes the possibility of moistureintrusion into the connector, and (2) it ensures that instruments withdisparities in the
21、hemispherical domes, or with domes not properlycentered over the receptor, are not operated in such a manner that theyamplify deviations from 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 referenc
22、e instrument must have a calibration at thedesired tilt angle; both instruments must be oriented at the tiltangle and facing the equator.4.4 The analog voltage signal from each radiometer ismeasured, digitized, and stored using a calibrated data-acquisition instrument, or system.Aminimum of fifteen
23、10 minmeasurement sequences are obtained, each sequence compris-ing a minimum of 21 instantaneous readings. It is preferablethat a 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 3
24、Transfer of calibration to both total and narrow-band ultra-violet radiometers may require a larger number of measurement sequencesin 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 Th
25、e data are mathematically ratioed, employing theinstrument constant of the reference instrument to determinethe instrument constant of the radiometer being calibrated. Themean value and the standard deviation are determined.5. Significance and Use5.1 The methods described represent the preferable me
26、ansfor calibration of field radiometers employing standard refer-ence radiometers. Other methods involve the employment ofan optical bench and essentially a point source of artificiallight. While these methods are useful for cosine and azimuthcorrection analyses, they suffer from foreground view fac
27、torand directionality problems. Transfer of calibration indoorsusing artificial sources is not covered by this test method.5.2 Traceability of calibration of global pyranometers isaccomplished when employing the method using a referenceglobal pyranometer that has been calibrated, and is traceable to
28、the World Radiometric Reference (WRR). For the purposes ofthis test method, traceability shall have been established if aparent instrument in the calibration chain participated in anInternational Pyrheliometric Comparison (IPC) conducted atthe World Radiation Center (WRC) in Davos, Switzerland.Trace
29、ability of calibration of narrow- and broad-band radiom-eters is accomplished when employing the method using areference ultraviolet radiometer that has been calibrated and istraceable to the National Institute of Standards and Technology(NIST), or other national standards organizations. See Zerlaut
30、4for a discussion of the WRR, the IPCs and their results.5.2.1 The reference global pyranometer (for example, onemeasuring hemispherical 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
31、absolute cavity pyrheliometer that participated ina WMO sanctioned IPCs (and therefore possesses a WRRreduction factor),5.2.1.2 An 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
32、.5.2.1.3 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 MeteorologicalOrganization (WMO) First Class pyranometer that was cali-brated by the sh
33、ading-disk method against an absolute cavitypyrheliometer possessing a WRR reduction factor, or by direct2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standar
34、ds 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 SolarResources, The MIT Press, Cambridge, MA, 1989, pp. 173308.E
35、824 102transfer from a WMO Standard Pyranometer (see WMOsGuide WMONo. 85for a discussion of the classification ofsolar radiometers).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
36、intercomparisons, shall be consid-ered suitable as the primary reference instrument.5.2.3 The reference ultraviolet radiometer, 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 h
37、ave been calibrated byone of the following:5.2.3.1 By comparison to a standard source of spectralirradiance that is traceable to NIST or to the appropriatenational standards organizations of other countries (usingappropriate filter correction factors),65.2.3.2 By comparison to the integrated spectra
38、l irradiancein the appropriate wavelength band of a spectroradiometer thathas itself been calibrated against such a standard source ofspectral irradiance, and5.2.3.3 By comparison to a spectroradiometer that hasparticipated in a regional or national Intercomparison ofSpectroradiometers, the results
39、of which are of referencequality.NOTE 5The calibration of reference ultraviolet radiometers using aspectroradiometer, or by 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 calibratio
40、n method employed assumes that theaccuracy of the values obtained are independent of time of yearwithin the constraints imposed 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 i
41、nstruments light receptor.5.4 The principal advantage of outdoor calibration of radi-ometers is that all types of radiometers 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 tha
42、t the naturalenvironment is not subject to control (but the calibrationstherefore include all of the instrumental characteristics of boththe reference and test radiometers that are influenced simulta-neously by the environment). Environmental circumstancessuch as ground reflectance or shading, or bo
43、th, must beminimized and affect both instruments similarly.5.6 The reference radiometer must be of the same type asthe test radiometer, since any difference in spectral sensitivitybetween instruments will result in erroneous calibrations. Thereader is referred to ISO TR 96737and ISO TR 99018fordiscu
44、ssions of the types of instruments available and their use.6. Interferences6.1 In order to minimize systematic errors the reference 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
45、 as possible.6.2 Sky ConditionsThe measurements selected in deter-mining the instrument constant shall be for periods of essen-tially uniform rates of change of radiation (either cloudless orovercast conditions). Periods selected shall be for 10 to 20 minsegments. Measurements selected under varying
46、 cloudy con-ditions may result in erroneous calibrations if the reference andtest radiometers possess significantly different 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 uncertai
47、nty of 60.2 % with an input imped-ance of at least 1 MV 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 f
48、or all horizontal and fixed angle tilt tests that islevel at 0 horizontal and that is adjustable in tilt over a suitablerange of angles from the horizontal.7.3 Tracking Calibration TableA precision calibrationtable required for normal incident calibrations and capable oftracking the sun to within 60
49、.5.8. Procedure8.1 Mount reference and test radiometers on a commoncalibration table in sunlight. Adjust both instruments to acommon elevation facing south for which a calibration value isavailable. Ensure that the azimuth reference marks point in acommon direction: For tilted or tracking calibrations, alsoensure that the electrical connector is pointed down (topreclude moisture intrusion), and that it is pointing to theequator (that is, south-facing in the northern hemisphere) ifused as the azimuth reference.8.2 Connect both the reference and test instrumen
