1、Designation: G 167 05Standard Test Method forCalibration of a Pyranometer Using a Pyrheliometer1This standard is issued under the fixed designation G 167; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、 number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONAccurate and precise measurements of total global (hemispherical) solar irradiance are required inthe assessment of irradiance and ra
3、diant exposure in the testing of exposed materials, determinationof the energy available to solar collection devices, and assessment of global and hemispherical solarradiation for meteorological purposes.This test method requires calibrations traceable to the World Radiometric Reference (WRR), which
4、represents the SI units of irradiance. The WRR is determined by a group of selected absolutepyrheliometers maintained by the World Meteorological Organization (WMO) in Davos, Switzerland.Realization of the WRR in the United States, and other countries, is accomplished by theintercomparison of absolu
5、te pyrheliometers with the World Radiometric Group (WRG) through aseries of intercomparisons that include the International Pyrheliometric Conferences held every fiveyears in Davos. The intercomparison of absolute pyrheliometers is covered by procedures adopted byWMO and is not covered by this test
6、method.It should be emphasized that “calibration of a pyranometer” essentially means the transfer of theWRR scale from a pyrheliometer to a pyranometer under specific experimental procedures.1. Scope1.1 This test method covers an integration of previous TestMethod E 913 dealing with the calibration
7、of pyranometerswith axis vertical and previous Test Method E 941 on calibra-tion of pyranometers with axis tilted. This amalgamation of thetwo methods essentially harmonizes the methodology with ISO9846.1.2 This test method is applicable to all pyranometersregardless of the radiation receptor employ
8、ed, and is applicableto pyranometers in horizontal as well as tilted positions.1.3 This test method is mandatory for the calibration of allsecondary standard pyranometers as defined by the WorldMeteorological Organization (WMO) and ISO 9060, and forany pyranometer used as a reference pyranometer in
9、thetransfer of calibration using Test Method E 842.1.4 Two types of calibrations are covered: Type I calibra-tions employ a self-calibrating, absolute pyrheliometer, andType II calibrations employ a secondary reference pyrheliom-eter as the reference standard (secondary reference pyrheliom-eters are
10、 defined by WMO and ISO 9060).1.5 Calibrations of reference pyranometers may be per-formed by a method that makes use of either an altazimuth orequatorial tracking mount in which the axis of the radiometersradiation receptor is aligned with the sun during the shadingdisk test.1.6 The determination o
11、f the dependence of the calibrationfactor (calibration function) on variable parameters is calledcharacterization. The characterization of pyranometers is notspecifically covered by this method.1.7 This test method is applicable only to calibration pro-cedures using the sun as the light source.1.8 T
12、his 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.2. Referenced Docume
13、nts2.1 ASTM Standards:2E 772 Terminology Relating to Solar Energy ConversionE 824 Test Method for Transfer of Calibration from Refer-ence to Field Radiometers2.2 WMO Document:World Meteorological Organization (WMO), “Measure-ment of Radiation” Guide to Meteorological Instruments1This test method is
14、under the jurisdiction of ASTM Committee G03 onWeathering and Durability and is the direct responsibility of Subcommittee G03.09on Radiometry.Current edition approved Oct. 1, 2005. Published November 2005. Originallyapproved in 2000. Last previous edition approved in 2000 as G 167 00.2For referenced
15、 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 standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
16、hohocken, PA 19428-2959, United States.and Methods of Observation, fifth ed., WMO-No. 8,Geneva32.3 ISO Standards:ISO 9060:1990 Solar EnergySpecification and Classifica-tion of Instruments for Measuring Hemispherical Solarand Direct Solar Radiation3ISO 9846:1993 Solar EnergyCalibration of a Pyranom-e
17、ter Using a Pyrheliometer33. Terminology3.1 Definitions:3.1.1 See Terminology E 772.3.2 Definitions of Terms Specific to This Standard:3.2.1 altazimuth mount, na tracking mount capable ofrotation about orthogonal altitude and azimuth axes; trackingmay be manual or by a follow-the-sun servomechanism.
18、3.2.2 calibration of a radiometer, vdetermination of theresponsivity (or the calibration factor, the reciprocal of theresponsivity) of a radiometer under well-defined measurementconditions.3.2.3 direct solar radiation, nthat component of solarradiation within a specified solid angle (usually 5.0 or
19、5.7)subtended at the observer by the suns solar disk, including aportion of the circumsolar radiation.3.2.4 diffuse solar radiation, nthat component of solarradiation scattered by the air molecules, aerosol particles, cloudand other particles in the hemisphere defined by the sky dome.3.2.5 equatoria
20、l mount, nsee Terminology E 772.3.2.6 field of view angle of a pyrheliometer, nfull angle ofthe cone which is defined by the center of the receiver surface(see ISO 9060, 5.1) and the border of the limiting aperture, ifthe latter are circular and concentric to the receiver surface; ifnot, effective a
21、ngles may be calculated (1, 2).43.2.7 global solar radiation, ncombined direct and dif-fuse solar radiation falling on a horizontal surface; solarradiation incident on a horizontal surface from the hemispheri-cal sky dome, or from 2p Steradian (Sr).3.2.8 hemispherical radiation, ncombined direct and
22、 dif-fuse solar radiation incident from a virtual hemisphere, or from2p Sr, on any inclined surface.3.2.8.1 DiscussionThe case of a horizontal surface isdenoted global solar radiation (3.2.7).3.2.9 pyranometer, nsee Terminology E 772.3.2.10 pyranometer, field, na pyranometer meeting WMOSecond Class
23、or better (that is, First Class) appropriate to fielduse and typically exposed continuously.3.2.11 pyranometer, reference, na pyranometer (see alsoISO 9060), used as a reference to calibrate other pyranometers,which is well-maintained and carefully selected to possessrelatively high stability and ha
24、s been calibrated using apyrheliometer.3.2.12 pyrheliometer, nsee Terminology E 772 and ISO9060.3.2.13 pyrheliometer, absolute (self-calibrating), na solarradiometer with a limited field of view configuration. The fieldof view should be approximately 5.0 and have a slope angle offrom 0.75 to 0.8, wi
25、th a blackened conical cavity receiver forabsorption of the incident radiation. The measured electricalpower to a heater wound around the cavity receiver constitutesthe method of self-calibration from first principles and trace-ability to absolute SI units. The self-calibration principlerelates to t
26、he sensing of the temperature rise of the receivingcavity by an associated thermopile when first the sun isincident upon the receiver and subsequently when the samethermopile signal is induced by applying precisely measuredpower to the heater with the pyrheliometer shuttered from thesun.3.2.14 shadi
27、ng-disk device, na device which allowsmovement of a disk in such a way that the receiver of thepyranometer to which it is affixed, or associated, is shadedfrom the sun. The cone formed between the origin of thereceiver and the disk subtends an angle that closely matches thefield of view of the pyrhe
28、liometer against which it is compared.Alternatively, and increasingly preferred, a sphere rather than adisk eliminates the need to continuously ensure the properalignment of the disk normal to the sun. See Appendix X1.3.2.15 slope angle, nthe angle defined by the difference inradii of the view limit
29、ing aperture (radius = R) and the receiverradius (= r) in a pyrheliometer. The slope angle, s,isthearctangent of R minus r divided by the distance between thelimiting aperture and the receiver surface, denoted by L:s =Tan-1(R r)/L. See Ref (1).3.2.16 thermal offset, na non-zero signal generated by a
30、radiometer when blocked from all sources of radiation. Be-lieved to be the result of infrared (thermal) radiation exchangesbetween elements of the radiometer and the environment.3.3 Acronyms:3.3.1 ACRAbsolute Cavity Radiometer3.3.2 ANSIAmerican National Standards Institute3.3.3 ARMAtmospheric Radiat
31、ionMeasurement Program3.3.4 DOEDepartment of Energy3.3.5 GUM(ISO) Guide to Uncertainty in Measurements3.3.6 IPCInternational Pyrheliometer comparison3.3.7 ISOInternational Standards Organization3.3.8 NCSLNational Council of Standards Laboratories3.3.9 NISTNational Institute of Standards and Technol-
32、ogy3.3.10 NRELNational Renewable Energy Laboratory3.3.11 PMODPhysical Meteorological Observatory Da-vos3.3.12 SACSingapore Accreditation Council3.3.13 SINGLASSingapore Laboratory Accreditation Ser-vice3.3.14 UKASUnited Kingdom Accrediation Service3.3.15 WRCWorld Radiation Center3.3.16 WRRWorld Radio
33、metric Reference3.3.17 WMOWorld Meteorological Organization4. Significance and Use4.1 The pyranometer is a radiometer designed to measurethe sum of directly solar radiation and sky radiation in suchproportions as solar altitude, atmospheric conditions and cloud3Available from American National Stand
34、ards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.G167052cover may produce. When tilted to the equator, by an angle b,pyranometers measure only hemispherical radiation falling inthe plan
35、e of the radiation receptor.4.2 This test method represents the only practical means forcalibration of a reference pyranometer. While the sun-trackers,the shading disk, the number of instantaneous readings, and theelectronic display equipment used will vary from laboratory tolaboratory, the method p
36、rovides for the minimum acceptableconditions, procedures and techniques required.4.3 While, in theory, the choice of tilt angle (b) is unlimited,in practice, satisfactory precision is achieved over a range oftilt angles close to the zenith angles used in the field.4.4 The at-tilt calibration as perf
37、ormed in the tilted positionrelates to a specific tilted position and in this position requiresno tilt correction. However, a tilt correction may be required torelate the calibration to other orientations, including axisvertical.NOTE 1WMO Fist Class pyranometers, or better, generally exhibit tilterr
38、ors of less than 1 % to tilts of 50 from the horizontal.4.5 Traceability of calibrations to the World RadiometricReference (WRR) is achieved through comparison to a refer-ence absolute pyrheliometer that is itself traceable to the WRRthrough one of the following:4.5.1 One of the International Pyrhel
39、iometric Comparisons(IPC) held in Davos, Switzerland since 1980 (IPC IV). SeeRefs (3-7).4.5.2 Any like intercomparison held in the United States,Canada or Mexico and sanctioned by the World MeteorologicalOrganization as a Regional Intercomparison of Absolute Cav-ity Pyrheliometers.4.5.3 Intercompari
40、son with any absolute cavity pyrheliom-eter that has participated in either and IPC or a WMO-sanctioned intercomparison within the past five years andwhich was found to be within 60.4 % of the mean of allabsolute pyrheliometers participating therein.4.6 The calibration method employed in this test m
41、ethodassumes that the accuracy of the values obtained are indepen-dent of time of year, with the constraints imposed and by thetest instruments temperature compensation circuit (neglectingcosine errors).5. Selection of Shade Method5.1 Alternating Shade Method:5.1.1 The alternating shade method is re
42、quired for a primarycalibration of the reference pyranometer used in the Continu-ous, Component-Summation Shade Method described in 5.2.5.1.2 The pyranometer under test is compared with apyrheliometer measuring direct solar irradiance (or, optionally,a continuously shaded control pyranometer; see Ap
43、pendixX3-Appendix X5). The voltage values from the pyranometerthat correspond to direct solar irradiance are derived from thedifference between the response of the pyranometer to hemi-spherical (unshaded) solar irradiance and the diffuse (shaded)solar irradiance. These response values (for example,
44、voltages)are induced periodically by means of a movable sun shadedisk. For the calculation of the responsivity, the differencebetween the unshaded and shaded irradiance signals is dividedby the direct solar irradiance (measured by the pyrheliometer)component that is normal to the receiver plane of t
45、he pyra-nometer.5.1.3 For meteorological purposes, the solid angle fromwhich the scattered radiative fluxes that represent diffuseradiation are measured shall be the total sky hemisphere,excluding a small solid angle around the suns disk.5.1.4 In addition to the basic method, modifications of thisme
46、thod that are considered to improve the accuracy of thecalibration factors, but which require more operational expe-rience, are presented in Appendix X3-Appendix X5.5.2 Continuous Sun-and-Shade Method (Component Sum-mation):5.2.1 The pyranometer is compared with two referenceradiometers, one of whic
47、h is a pyrheliometer and the other awell-calibrated reference pyranometer equipped with a track-ing shade disk or sphere to measure diffuse solar radiation. Thereference pyranometer shall be either calibrated using thealternating sun-and shade method described in 5.1, or shall becompared against suc
48、h a pyranometer in accordance with TestMethod E 824.5.2.2 Global solar irradiance (or hemispherical solar irradi-ance for inclined pyranometers) is determined by the sum ofthe direct solar irradiance measured with a pyrheliometermultiplied by the cosine of the incidence angle of the beam tothe local
49、 horizontal (or inclined plane parallel to the radiometersensor), plus the diffuse solar irradiance measured with ashaded reference pyranometer mounted in the same configu-ration (tilted or horizontal) as the unit under test.5.2.3 The smallest uncertainty realized in the calibration ofpyranometers will occur when the pyrheliometer is a self-calibrating absolute cavity pyrheliometer and when the refer-ence pyranometer has itself been calibrated over a range of airmass (zenith angle) by the component summation (continuousshade) method usin
