1、Designation: G207 11Standard Test Method forIndoor Transfer of Calibration from Reference to FieldPyranometers1This standard is issued under the fixed designation G207; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. 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
3、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 ascertain the energy available to solar collection devices such as flat-platecollectors, and (3) the a
4、ssessment 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 b
5、e of interest, including both total and narrow-band ultraviolet radiantexposure.This test method for indoor transfer of calibration from reference to field instruments is onlyapplicable to pyranometers and radiometers whose field angles closely approach 180 . instrumentswhich therefore may be said t
6、o measure hemispherical radiation, or all radiation incident on a flatsurface. Hemispherical radiation includes both the direct and sky (diffuse) geometrical components ofsunlight, while global solar irradiance refers only to hemispherical irradiance on a horizontal surfacesuch that the field of vie
7、w includes the entire hemispherical sky dome.For the purposes of this test method, the terms pyranometer and radiometer are used interchangeably.1. Scope1.1 The method described in this standard applies to theindoor transfer of calibration from reference to field radiom-eters to be used for measurin
8、g and monitoring outdoor radiantexposure levels.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 method employs theuse of ar
9、tificial light sources (lamps).1.4 Calibrations of field radiometers are performed withsensors horizontal (at 0 tilt from the horizontal to the earth).The essential requirement is that the reference radiometer shallhave been calibrated at horizontal tilt as employed in thetransfer of calibration.1.5
10、 The primary reference instrument shall not be used as afield instrument and its exposure to sunlight shall be limited tooutdoor calibration or intercomparisons.NOTE 1At a laboratory where calibrations are performed regularly itis advisable to maintain a group of two or three reference radiometers t
11、hatare 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 method of calibration specified for total solarpyranom
12、eters shall be traceable to the World RadiometricReference (WRR) through the calibration methods of thereference standard instruments (Method G167 and Test MethodE816), and the method of calibration specified for narrow- andbroad-band ultraviolet radiometers shall be traceable to theNational Institu
13、te of Standards and Technology (NIST), orother internationally recognized national standards laboratories(Standard G138).1This test method is under the jurisdiction of ASTM Committee G03 onWeathering and Durability and is the direct responsibility of Subcommittee G03.09on Radiometry.Current edition
14、approved July 1, 2011. Published August 2011. DOI: 10.1520/G0207111Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresp
15、onsibility 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.2. Referenced Documents2.1 ASTM Standards:2E772 Terminology Relating to Solar Energy ConversionE816 Test Method for Calibration of Pyr
16、heliometers byComparison to Reference PyrheliometersE824 Test Method for Transfer of Calibration From Refer-ence to Field RadiometersG113 Terminology Relating to Natural andArtificial Weath-ering Tests of Nonmetallic MaterialsG138 Test Method for Calibration of a SpectroradiometerUsing a Standard So
17、urce of IrradianceG167 Test Method for Calibration of a Pyranometer Usinga Pyrheliometer2.2 Other Standards:3ISO 9847 Solar Energy Calibration of Field Pyranometersby Comparison to a Reference Pyranometer3. Terminology3.1 Definitions:3.1.1 See Terminology E772 and G113 for terminologyrelating to thi
18、s test method.4. Summary of Test Method4.1 Mount the reference pyranometer, and the field (or test)radiometers, or pyranometers, on a common calibration tablefor horizontal calibration. Adjust the height of the radiationreceptor of all instruments to a common elevation.4.2 Connect the signal cables
19、from the reference and testsensors to a data acquisition system.4.3 Adjust the data acquisition system to record data at theselected data collection interval.NOTE 2Data collection interval should be function of the timeconstant of the sensor. Sensor time constant is the period of time requiredfor a
20、sensor to reach 1 1/e = 63% of the maximum minus the minimumamplitude of a step change in input stimulus. (e is base of naturallogarithms, 2.718282.). Often, “one over e” (1/e) time constants arereported for radiation sensors, for example “1/e response time = 3seconds”. This represents the time for
21、the sensor signal to reach 37% ofthe full range step change representing the step change in the stimulus.Four times the 1/e time constant can be considered the time for the sensorto fully respond to a step change in stimulus.4.4 Energize the source to be used for the transfer ofcalibration.NOTE 3It
22、is mandatory that the spectral distribution of the source beknown or well characterized. Indoor calibration transfers between narrowband radiometers such as Ultraviolet and Photopic detectors shall beaccomplished using sources with spectral irradiance distributions assimilar as possible to the spect
23、ral distribution of the sources to bemonitored. This will reduce spectral mismatch errors arising fromdifferences in the spectral response of sensors and dissimilar calibrationand test source spectral distributions. In the special case of pyranometersfor solar radiation measurements, as long as the
24、reference radiometer hasa relatively flat and broad (greater than 700 nm passband) spectralresponse (for example, black thermopile), or has been calibrated outdoors,the difference between calibration and source spectral distributions is lessimportant, however should be taken into consideration.4.5 M
25、onitor the output signal of the reference radiometer atthe selected data collection interval.4.6 Ensure the temporal stability of the source, as indicatedby the reference radiometer output, has stabilized at reasonableamplitude. Recommended source amplitude for broadbandsolar radiometers is in the r
26、ange 500 Wm-2to 1000 Wm-2. Fornarrowband radiometers, a source amplitude (spectral irradi-ance distribution integrated over with respect to wavelengthover the pass band of the radiometers) of 50% to 125% of thepeak amplitude to be expected in the source monitored by thetest instruments is recommende
27、d.4.7 The analog voltage signal from each radiometer ismeasured, digitized, and stored using a calibrated data-acquisition instrument, or system. A minimum of 30 datareadings is required.4.8 The test data are divided by the reference radiometerdata, employing the instrument constant of the reference
28、instrument to determine the instrument constant of the radiom-eter being calibrated. The mean value, the standard deviation,and coefficient of variation are determined.5. Significance and Use5.1 The methods described represent a means for calibrationof field radiometers employing standard reference
29、radiometersindoors. Other methods involve the natural sunlight outdoorsunder clear skies, and various combinations of referenceradiometers. Outdoor these methods are useful for cosine andazimuth correction analyses, but may suffer from a lack ofavailable clear skies, foreground view factor and direc
30、tionalityproblems. Outdoor transfer of calibrations is covered bystandards G167, E816, and E824.5.2 Several configurations of artificial sources are possible,including:5.2.1 Point sources (lamps) at a distance, to which thesensors are exposed5.2.2 Extended sources (banks of lamps, or lamp(s) behindd
31、iffusing or “homogenizing” screens) to which the sensors areexposed5.2.3 Various configurations of enclosures (usually spheri-cal or hemispherical) with the interior walls illuminatedindirectly with lamps. The sensors are exposed to the radiationemanating from the enclosure walls.5.3 Traceability of
32、 calibration for pyranometers is accom-plished when employing the method using a reference globalpyranometer that has been calibrated, and is traceable to theWorld Radiometric Reference (WRR)4. For the purposes of2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu
33、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Available from International Standards Organization (ISO), 1Rue De Varembre, Geneva, Switzerland CH-1211 204WMONo. 8, “Guide to Mete
34、orological Instruments and Methods of Obser-vation,” Fifth Ed., World Meteorological Organization, Geneva, Switzerland, 1983G207 112this test method, traceability shall have been established if aparent instrument in the calibration chain can be traced to areference pyrheliometer which has participat
35、ed in an Interna-tional Pyrheliometric Comparison (IPC) conducted at theWorld Radiation Center, (WRC), Davos, Switzerland.5.3.1 The reference global pyranometer (for example, onemeasuring hemispherical solar radiation at all wavelengths)shall have been calibrated by the shading-disk, componentsummat
36、ion, or outdoor comparison method against one of thefollowing instruments:5.3.1.1 An absolute cavity pyrheliometer that participated ina World Meteorological Organization (WMO) sanctionedIPCs (and therefore possesses a WRR reduction factor).5.3.1.2 An absolute cavity radiometer that has been inter-c
37、ompared (in a local or regional comparison) with an absolutecavity pyrheliometer meeting 5.3.1.1.5.3.1.3 Alternatively, the reference pyranometer may havebeen calibrated by direct transfer from a World MeteorologicalOrganization (WMO) First Class pyranometer that was cali-brated by the shading-disk
38、method against an absolute cavitypyrheliometer possessing a WRR reduction factor, or by directtransfer from a WMO Standard Pyranometer (see WMOsGuide WMONo. 8 for a discussion of the classification ofsolar radiometers). See Zerlaut5for a discussion of the WRR,the IPCs and their results.NOTE 4Any of
39、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.5.4 Traceability of calibration of narrow band (for example,U
40、ltraviolet) radiometers is accomplished when employing themethod using a reference narrow band radiometer that has beencalibrated and is traceable to the National Institute of Standardsand Technology (NIST), or other national standards organiza-tions.5.4.1 The reference narrow band radiometer, regar
41、dless 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:5.4.1.1 By comparison to a standard source of spectralirradiance that is traceable to NIST
42、 or to the appropriatenational standards organizations of other countries using ap-propriate filters and filter correction factors for example,Drummond6.5.4.1.2 By comparison of the radiometer output to theintegrated spectral irradiance in the appropriate wavelengthband of a spectroradiometer that h
43、as itself been calibratedagainst such a standard source of spectral irradiance,5.4.1.3 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
44、 radiometers using aspectroradiometer, or by direct calibration against standard sources ofspectral irradiance (for example, deuterium or 1000 W tungsten-halogenlamps) is the subject of Standard G138.5.5 The calibration method employed assumes that theaccuracy of the values obtained with respect to
45、the calibrationsource used are applicable to the deployed environment, withadditional sources of uncertainty due to logging equipment andenvironmental effects above and beyond the calibration uncer-tainty.5.6 The principal advantages of indoor calibration of radi-ometers are user convenience, lack o
46、f dependence on weather,and user control of test conditions.5.7 The principal disadvantages of the indoor calibrationsare the possible differences between natural environmentalinfluences and the laboratory calibration conditions with re-spect to the spectral and spatial distribution of the sourcerad
47、iation (sun and sky versus lamps or enclosure walls).5.8 It is recommended that the reference radiometer be ofthe same type as the test radiometer, since any difference inspectral sensitivity between instruments will result in errone-ous calibrations. However, The calibration of sufficientlybroadban
48、d detectors (approximately 700 nm or more), such asilicon photodiode detectors with respect to extremely broad-band (more than 2000 nm) thermopile radiometers is accept-able, as long as the additional increased uncertainty in the fieldmeasurements, due to spectral response and spectral mismatchlimit
49、ations, is acceptable. The reader is referred to ISO TR96737and ISO TR 99018for discussions of the types ofinstruments 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 should be as nearly identical as possible.6.1.2 The spectral content (spectral power distribution) ofthe calibration source and the source to be monitored in thefield experiment should be matched to greatest extent
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