1、Designation: E 816 05Standard Test Method forCalibration of Pyrheliometers by Comparison to ReferencePyrheliometers1This standard is issued under the fixed designation E 816; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A 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 measurement of the direct (beam) radiation component of sunlight are requiredin (1) the cali
3、bration of reference pyranometers by the shading disk or optical occluding methods, (2)determination of the energy collected by concentrating solar collectors, including exposure levelsachieved in use of Practice G90dealing with Fresnel-reflecting concentrator test machines, and (3)the assessment of
4、 the direct beam for energy budget analyses, geographic mapping of solar energy, andas an aid in the determination of the concentration of aerosol and particulate pollution, and water vaporeffects.This test method requires calibration to theWorld Radiometric Reference (WRR), maintained by theWorld M
5、eteorological Organization (WMO), Geneva. The Intercomparison of Absolute CavityPyrheliometers, also called Absolute Cavity Radiometers, on which the WRR depends, is covered byprocedures adopted by WMO and by various U.S. Organizations who occasionally convene suchintercomparisons for the purpose of
6、 transferring the WRR to the United States, and to maintaining theWRR in the United States. These procedures are not covered by this test method.1. Scope1.1 This test method has been harmonized with, and istechnically equivalent to, ISO 9059.1.2 Two types of calibrations are covered by this testmeth
7、od. One is the calibration of a secondary referencepyrheliometer using an absolute cavity pyrheliometer as theprimary standard pyrheliometer, and the other is the transfer ofcalibration from a secondary reference to one or more fieldpyrheliometers. This test method proscribes the calibrationprocedur
8、es and the calibration hierarchy, or traceability, fortransfer of the calibrations.NOTE 1It is not uncommon, and is indeed desirable, for both thereference and field pyrheliometers to be of the same manufacturer andmodel designation.1.3 This test method is relevant primarily for the calibrationof re
9、ference pyrheliometers with field angles of 5 to 6, usingas the primary reference instrument a self-calibrating absolutecavity pyrheliometer having field angles of about 5. Pyrheli-ometers with field angles greater than 6.5 shall not bedesignated as reference pyrheliometers.1.4 When this test method
10、 is used to transfer calibration tofield pyrheliometers having field angles both less than 5 orgreater than 6.5, it will be necessary to employ the proceduredefined by Angstrom and Rodhe.21.5 This test method requires that the spectral response ofthe absolute cavity chosen as the primary standard py
11、rheliom-eter be nonselective over the range from 0.3 to 10-mwavelength. Both reference and field pyrheliometers coveredby this test method shall be nonselective over a range from 0.3to 4-m wavelength.1.6 The primary and secondary reference pyrheliometersshall not be field instruments and their expos
12、ure to sunlightshall be limited to calibration or intercomparisons. Thesereference instruments shall be stored in an isolated cabinet orroom equipped with standard laboratory temperature andhumidity control.NOTE 2At a laboratory where calibrations are performed regularly, itis advisable to maintain
13、a group of two or three secondary referencepyrheliometers that are included in every calibration. These serve ascontrols to detect any instability or irregularity in the standard referencepyrheliometer.1.7 This test method is applicable to calibration proceduresusing natural sunshine only.1This test
14、 method is 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 1981. Last previous edition approved in 2002 as E 816 95 (200
15、2).2Angstrom, A., and Rodhe, B., “Pyrheliometric Measurements with SpecialRegard to the Circumsolar Sky Radiation,” Tellus, Vol 18, 1966, pp. 2533.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2. Referenced Documents2.1 ASTM Standa
16、rds:3E 772 Terminology Relating to Solar Energy ConversionE 824 Test Method for Transfer of Calibration from Refer-ence to Field RadiometersG90 Practice for Performing Accelerated Outdoor Weath-ering of Nonmetallic Materials Using Concentrated Natu-ral SunlightG 167 Test Method for Calibration of a
17、Pyranometer Usinga Pyrheliometer2.2 ISO Standards:ISO 9059 Calibration of Field Pyrheliometers by Compari-son to a Reference Pyrheliometer4ISO 9060 Specification and Classification of Instrumentsfor Measuring Hemispherical Solar and Direct SolarRadiation4ISO TR 9673 The Instrumental Measurement of S
18、unlightfor Determining Exposure Levels4ISO 9846 Calibration of a Pyranometer Using a Pyrheliom-eter42.3 WMO Standard:Guide to Meteorological Instruments and Methods of Ob-servation, Fifth ed., WMO-No. 853. Terminology3.1 Definitions:3.1.1 The relevant definitions of Terminology E 772 applyto the cal
19、ibration method described in this test method.3.1.2 absolute cavity pyrheliometersee self-calibratingabsolute cavity pyrheliometer.3.1.3 direct radiation, direct solar radiation, and direct(beam) radiationradiation received from a small solid anglecentered on the suns disk, on a given plane (see ISO
20、 9060).That component of sunlight is the beam between an observer,or instrument, and the sun within a solid conical angle centeredon the suns disk and having a total included planar field angleof, for the purposes of this test method, 5 to 6.3.1.4 field pyrheliometerpyrheliometers that are designeda
21、nd used for long-term field measurements of direct solarradiation. These pyrheliometers are weatherproof and thereforepossess windows, usually quartz, at the field aperture that passall solar radiation in the range from 0.3 to 4-m wavelength.3.1.5 opening anglewith radius of field aperture denotedby
22、 R and the distance between the field and receiver aperturesdenoted by l, the opening angle is defined for right circularcones by the equation:Zo5 tan21R/l (1)The field angle is double the opening angle.3.1.6 primary standard pyrheliometerspyrheliometers,selected from the group of absolute pyrheliom
23、eters (see self-calibrating absolute cavity pyrheliometer).3.1.7 reference pyrheliometerpyrheliometers of any cat-egory serving as a reference in calibration transfer procedures.They are selected and well-tested instruments (see Table 2 ofISO 9060), that have a low rate of yearly change in responsiv
24、-ity. The reference pyrheliometer may be of the same type,class, and manufacturer as the field radiometers in which caseit is specially chosen for calibration transfer purposes and istermed a secondary standard pyrheliometer (see ISO 9060), orit may be of the self-calibrating cavity type (see self-c
25、alibrating absolute cavity pyrheliometer).3.1.8 secondary standard pyrheliometerpyrheliometers ofhigh precision and stability whose calibration factors arederived from primary standard pyrheliometers. This groupcomprises absolute cavity pyrheliometers that do not fulfill therequirements of a primary
26、 standard pyrheliometer as describedin 3.1.6.3.1.9 self-calibrating absolute cavity pyrheliometera ra-diometer consisting of either a single- or dual-conical heatedcavity that, during the self-calibration mode, displays thepower required to produce a thermopile reference signal that isidentical to t
27、he sampling signal obtained when viewing the sunwith an open aperture. The reference signal is produced by thethermopile in response to the cavity irradiance resulting fromheat supplied by a cavity heater with the aperture closed.3.2 Acronyms:3.2.1 ACRAbsolute Cavity Radiometer3.2.2 ANSIAmerican Nat
28、ional Standards Institute3.2.3 ARMAtmospheric RadiationMeasurement Program3.2.4 DOEDepartment of Energy3.2.5 GUM(ISO) Guide to Uncertainty in Measurements3.2.6 IPCInternational Pyrheliometer comparison3.2.7 ISOInternational Standards Organization3.2.8 NCSLNational Council of Standards Laboratories3.
29、2.9 NISTNational Institute of Standards and Technol-ogy3.2.10 NRELNational Renewable Energy Laboratory3.2.11 PMODPhysical Meteorological Observatory Da-vos3.2.12 SACSingapore Accreditation Council3.2.13 SINGLASSingapore Laboratory Accreditation Ser-vice3.2.14 UKASUnited Kingdom Accrediation Service3
30、.2.15 WRCWorld Radiation Center3.2.16 WRRWorld Radiometric Reference3.2.17 WMOWorld Meteorological Organization4. Significance and Use4.1 Though the sun trackers employed, the number ofinstantaneous readings, and the data acquisition equipmentused will vary from instrument to instrument and from lab
31、o-ratory to laboratory, this test method provides for the minimumacceptable conditions, procedures, and techniques required.4.2 While the greatest accuracy will be obtained whencalibrating pyrheliometers with a self-calibrating absolutecavity pyrheliometer that has been demonstrated by intercom-pari
32、son to be within 60.5 % of the mean irradiance of a familyof similar absolute instruments, acceptable accuracy can beachieved by careful attention to the requirements of this test3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
33、 For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.5Available from World Meterological Organization, Geneva, Switzerland.E8160
34、52method when transferring calibration from a secondary refer-ence to a field pyrheliometer.4.3 By meeting the requirements of this test method, trace-ability of calibration to the World Radiometric Reference(WRR) can be achieved through one or more of the followingrecognized intercomparisons:4.3.1
35、International Pyrheliometric Comparison (IPC) VII,Davos, Switzerland, held in 1990, and every five years there-after, and the PMO-2 absolute cavity pyrheliometer that is theprimary reference instrument of WMO.64.3.2 Any WMO-sanctioned intercomparison of self-calibrating absolute cavity pyrheliometer
36、s held in WMO Re-gion IV (North and Central America).4.3.3 Any sanctioned or non-sanctioned intercomparisonheld in the United States the purpose of which is to transfer theWRR from the primary reference absolute cavity pyrheliom-eter maintained as the primary reference standard of the UnitedStates b
37、y the National Oceanic and Atmospheric Administra-tions Solar Radiation Facility in Boulder, CO.74.3.4 Any future intercomparisons of comparable referencequality in which at least one self-calibrating absolute cavitypyrheliometer is present that participated in IPC VII or asubsequent IPC, and in whi
38、ch that pyrheliometer is treated asthe intercomparisons reference instrument.4.3.5 Any of the absolute radiometers participating in theabove intercomparisons and being within 60.5 % of the meanof all similar instruments compared in any of those intercom-parisons.4.4 The calibration transfer method e
39、mployed assumes thatthe accuracy of the values obtained are independent of time ofyear and, within the constraints imposed, time of day ofmeasurements. With respect to time of year, the requirementfor normal incidence dictates a tile angle from the horizontalthat is dependent on the suns zenith angl
40、e and, thus, the airmass limits for that time of year and time of day.5. Interferences5.1 Radiation SourceTransfer of calibration from refer-ence to secondary standard or field pyrheliometers is accom-plished by exposing the two instruments to the same radiationfield and comparing their correspondin
41、g measurands. Thedirect irradiance should not be less than 300 Wm2, butirradiance values exceeding 700 Wm2is preferred.5.2 Sky ConditionsThe measurements made in determin-ing the instrument constant shall be performed only underconditions when the sun is unobstructed by clouds for anincremental data
42、-taking period. The most acceptable sky con-ditions should be such that the direct irradiance is not less than80 % of the hemispherical irradiance measured with a pyra-nometer aligned with its axis vertical and calibrated in accor-dance with Test Method G 167. Also, no cloud formation maybe within 1
43、5 of the sun during the period data are taken forrecord when either transferring calibration to a secondarystandard pyrheliometer (to be used as a reference pyrheliom-eter) from an absolute cavity pyrheliometer, or when transfer-ring calibration from a secondary reference pyrheliometer tofield pyrhe
44、liometers. Generally, good calibration conditionsexist when the cloud cover is less than 12.5 %.NOTE 3Contrails of airplanes that are within 15 of the sun can betolerated providing the ratio of so affected measurements to unaffectedmeasurements is small in any series.NOTE 4Atmospheric water vapor in
45、 the pre-condensation phaseoccasionally causes variable atmospheric transmission. Generally, thescattering of measuring data that is produced by these clusters isacceptable.5.2.1 The atmospheric turbidity during transfer of calibra-tion should be close to values typical for the field measuringcondit
46、ions. Generally, the turbidity should be confined toconditions with Linke turbidity factors lower than six (seeISO 9059 and ISO 9060).5.2.2 The circumsolar radiation (aureole) originates fromforward scattering of direct solar radiation. It decreases fromthe limb of the sun to an angular distance of
47、about 15 byseveral orders of magnitude, depending on the type andconcentration of the aerosol.2,8,9The typical amount of circum-solar radiation within an angular distance of 5 of the sunrepresents only a few percent of the direct solar radiation. Ifstandard and field pyrheliometers have different fi
48、eld-of-viewangles, the aerosol may strongly influence the accuracy of thetransfer of calibration. Calculated percentages of circumsolarcontained in direct solar radiation, for different aerosol typesand solar elevation angles, are given for information inAppendix X1.5.3 Differences in GeometryIf the
49、 pyrheliometers beingcompared do not have similar opening angles, atmosphericturbidity will introduce errors into the calibration.25.4 Wind ConditionsWind conditions are known to affectinstruments differently, particularly some self-calibrating abso-lute cavity pyrheliometers, particularly when the wind isblowing from the direction of the suns azimuth (630).Measurements affected by wind conditions should be rejected.A tolerable maximum wind speed for unprotected measure-ment conditions cannot be specified.NOTE 5Pyrheliometers
