G03.09 - Radiometry

SIGNIFICANCE AND USE
5.1 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight as in Test Methods E972, G130, and G207.  
5.2 The purpose of this test method is to foster greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
5.3 Changes in the optical properties of materials such as spectral reflectance, transmittance, or absorptance are often the measure of material stability or usefulness in various applications. Computation of the material responses to exposure to radiant sources mentioned above requires the integration of measured wavelength-dependent digital data, sometimes in conjunction with tabulated wavelength-dependent reference or comparison data.  
5.4 This test method specifies and describes the Modified Trapezoid Rule as a single reasonably accurate and easily implemented integration technique for computing approximations of spectral source and optical property integrals.  
5.5 The method includes a procedure for estimating the approximate absolute and relative (percent) error in the estimated spectral integrals.  
5.6 The method includes a procedure to construct data sets that match in spectral wavelength and spectral wavelength interval, which does not have to be uniform over the spectral range of interest. Uniform spectral intervals simplify some of the calculations, but are not required.
SCOPE
1.1 This test method specifies a single relatively simple method to implement, common integration technique, the Modified Trapezoid Rule, to integrate digital or tabulated spectral data. The intent is to produce greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
1.2 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight. Changes in the spectrally dependent optical properties of materials, in combination with exposure source spectral data, are often used to evaluate the effect of exposure to radiant sources, develop activation spectra (Practice G178), and classify, evaluate, or rate sources with respect to reference or exposure source spectral distributions. Another important application is the integration of the original spectrally dependent optical properties of materials in combination with exposure source spectral data to determine the total energy absorbed by a material from various exposure sources.  
1.3 The data applications described in 1.2 often require the use of tabulated reference spectral distributions, digital spectral data produced by modern instrumentation, and the integrated version of that data, or combinations (primarily multiplication) of spectrally dependent data.  
1.4 Computation of the material responses to exposure to radiant sources mentioned above require the integration of measured wavelength dependent digital data, sometimes in conjunction with tabulated wavelength dependent reference or comparison data.  
1.5 The term “integration” in the previous sections refers to the numerical approximation to the true integral of continuous functions, represented by discrete, digital data. There are numerous mathematical techniques for performing numerical integration. Each method provides different levels of complexity, accuracy, ease of implementation and computational efficiency, an...

SIGNIFICANCE AND USE
4.1 Though the sun trackers employed, the number of instantaneous readings, and the data acquisition equipment used will vary from instrument to instrument and from laboratory to laboratory, this test method provides for the minimum acceptable conditions, procedures, and techniques required.  
4.2 While the greatest accuracy will be obtained when calibrating pyrheliometers with a self-calibrating absolute cavity pyrheliometer that has been demonstrated by intercomparison to be within ±0.5 % of the mean irradiance of a family of similar absolute instruments, acceptable accuracy can be achieved by careful attention to the requirements of this test method when transferring calibration from a secondary reference to a field pyrheliometer.  
4.3 By meeting the requirements of this test method, traceability of calibration to the World Radiometric Reference (WRR) can be achieved through one or more of the following recognized intercomparisons:  
4.3.1 International Pyrheliometric Comparison (IPC) VII, Davos, Switzerland, held in 1990, and every five years thereafter, and the PMO-2 absolute cavity pyrheliometer that is the primary reference instrument of WMO.6  
4.3.2 Any WMO-sanctioned intercomparison of self-calibrating absolute cavity pyrheliometers held in WMO Region IV (North and Central America).  
4.3.3 Any sanctioned or non-sanctioned intercomparison held in the United States the purpose of which is to transfer the WRR from the primary reference absolute cavity pyrheliometer maintained as the primary reference standard of the United States by the National Oceanic and Atmospheric Administration's Solar Radiation Facility in Boulder, CO.7  
4.3.4 Any future intercomparisons of comparable reference quality in which at least one self-calibrating absolute cavity pyrheliometer is present that participated in IPC VII or a subsequent IPC, and in which that pyrheliometer is treated as the intercomparison's reference instrument.  
4.3.5 Any of the absolute radiometers p...
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1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.  
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method prescribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.
Note 1: It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.  
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5° to 6°, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5°. Pyrheliometers with field angles greater than 6.5° shall not be designated as reference pyrheliometers.  
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5° or greater than 6.5°, it will be necessary to employ the procedure defined by Angstrom and Rodhe.2  
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 μm to 10 μm wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 μm to 4 μm wavelength.  
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.
Note 2: At a laboratory where cali...

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1.1 This practice describes deployment conditions, maintenance requirements, verification procedures and calibration frequencies for use of pyranometers, pyrheliometers and UV radiometers in outdoor testing environments. This practice also discusses the conditions that dictate the level of accuracy required for instruments of different types.  
1.2 While both pyranometers and UV radiometers may be employed indoors to measure light radiation sources, the measurement of ultraviolet and light radiation in accelerated weathering enclosures using manufactured light sources generally requires specialized radiometric instruments. Use of radiometric instrumentation to measure laboratory light sources is covered in ISO 9370.
Note 1: An ASTM standard that is similar to ISO 9370 is under development and deals with the instrumental determination of irradiance and radiant exposure in weathering tests.  
1.3 The characterization of radiometers is outside the scope of the activities required of users of radiometers, as contemplated by this standard.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
4.1 The pyranometer is a radiometer designed to measure the sum of directly solar radiation and sky radiation in such proportions as solar altitude, atmospheric conditions and cloud cover may produce. When tilted to the equator, by an angle β, pyranometers measure only hemispherical radiation falling in the plane of the radiation receptor.  
4.2 This test method represents the only practical means for calibration of a reference pyranometer. While the sun-trackers, the shading disk, the number of instantaneous readings, and the electronic display equipment used will vary from laboratory to laboratory, the method provides for the minimum acceptable conditions, procedures and techniques required.  
4.3 While, in theory, the choice of tilt angle (β) is unlimited, in practice, satisfactory precision is achieved over a range of tilt angles close to the zenith angles used in the field.  
4.4 The at-tilt calibration as performed in the tilted position relates to a specific tilted position and in this position requires no tilt correction. However, a tilt correction may be required to relate the calibration to other orientations, including axis vertical.
Note 1: WMO High Quality pyranometers generally exhibit tilt errors of less than 0.5 %. Tilt error is the percentage deviation from the responsivity at 0° tilt (horizontal) due to change in tilt from 0° to 90° at 1000 W·m23.  
4.5 Traceability of calibrations to the World Radiometric Reference (WRR) is achieved through comparison to a reference absolute pyrheliometer that is itself traceable to the WRR through one of the following:  
4.5.1 One of the International Pyrheliometric Comparisons (IPC) held in Davos, Switzerland since 1980 (IPC IV). See Refs (3-7).  
4.5.2 Any like intercomparison held in the United States, Canada or Mexico and sanctioned by the World Meteorological Organization as a Regional Intercomparison of Absolute Cavity Pyrheliometers.  
4.5.3 Intercomparison with any absolute cavity pyrheliometer t...
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1.1 This test method covers an integration of previous Test Method E913 dealing with the calibration of pyranometers with axis vertical and previous Test Method E941 on calibration of pyranometers with axis tilted. This amalgamation of the two methods essentially harmonizes the methodology with ISO 9846.  
1.2 This test method is applicable to all pyranometers regardless of the radiation receptor employed, and is applicable to pyranometers in horizontal as well as tilted positions.  
1.3 This test method is mandatory for the calibration of all secondary standard pyranometers as defined by the World Meteorological Organization (WMO) and ISO 9060, and for any pyranometer used as a reference pyranometer in the transfer of calibration using Test Method E842.  
1.4 Two types of calibrations are covered: Type I calibrations employ a self-calibrating, absolute pyrheliometer, and Type II calibrations employ a secondary reference pyrheliometer as the reference standard (secondary reference pyrheliometers are defined by WMO and ISO 9060).  
1.5 Calibrations of reference pyranometers may be performed by a method that makes use of either an altazimuth or equatorial tracking mount in which the axis of the radiometer's radiation receptor is aligned with the sun during the shading disk test.  
1.6 The determination of the dependence of the calibration factor (calibration function) on variable parameters is called characterization. The characterization of pyranometers is not specifically covered by this method.  
1.7 This test method is applicable only to calibration procedures using the sun as the light source.  
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.9 This interna...

SIGNIFICANCE AND USE
5.1 The uncertainty in outdoor solar irradiance measurement has a significant impact on weathering and durability and the service lifetime of materials systems. Accurate solar irradiance measurement with known uncertainty will assist in determining the performance over time of component materials systems, including polymer encapsulants, mirrors, Photovoltaic modules, coatings, etc. Furthermore, uncertainty estimates in the radiometric data have a significant effect on the uncertainty of the expected electrical output of a solar energy installation.  
5.1.1 This influences the economic risk analysis of these systems. Solar irradiance data are widely used, and the economic importance of these data is rapidly growing. For proper risk analysis, a clear indication of measurement uncertainty should therefore be required.  
5.2 At present, the tendency is to refer to instrument datasheets only and take the instrument calibration uncertainty as the field measurement uncertainty. This leads to over-optimistic estimates. This guide provides a more realistic approach to this issue and in doing so will also assists users to make a choice as to the instrumentation that should be used and the measurement procedure that should be followed.  
5.3 The availability of the adjunct (ADJG021317)5 uncertainty spreadsheet calculator provides real world example, implementation of the GUM method, and assists to understand the contribution of each source of uncertainty to the overall uncertainty estimate. Thus, the spreadsheet assists users or manufacturers to seek methods to mitigate the uncertainty from the main uncertainty contributors to the overall uncertainty.
SCOPE
1.1 This guide provides guidance and recommended practices for evaluating uncertainties when calibrating and performing outdoor measurements with pyranometers and pyrheliometers used to measure total hemispherical- and direct solar irradiance. The approach follows the ISO procedure for evaluating uncertainty, the Guide to the Expression of Uncertainty in Measurement (GUM) JCGM 100:2008 and that of the joint ISO/ASTM standard ISO/ASTM 51707 Standard Guide for Estimating Uncertainties in Dosimetry for Radiation Processing, but provides explicit examples of calculations. It is up to the user to modify the guide described here to their specific application, based on measurement equation and known sources of uncertainties. Further, the commonly used concepts of precision and bias are not used in this document. This guide quantifies the uncertainty in measuring the total (all angles of incidence), broadband (all 52 wavelengths of light) irradiance experienced either indoors or outdoors.  
1.2 An interactive Excel spreadsheet is provided as adjunct, ADJG021317. The intent is to provide users real world examples and to illustrate the implementation of the GUM method.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Products exposed outdoors degrade due to primarily three stress factors: sunlight, temperature and moisture. The rate of property change is a function of time and stressors’ intensity.  
5.2 Whereas the UV irradiance calculated in this practice is independent of material, it is especially relevant to polymeric materials exposed outdoors as the combined action of UV radiation and oxygen is often the dominant factor leading to their degradation. Therefore, estimating UV irradiance is an important parameter to assess the service life of products.  
5.3 UV radiant dosage is often more important to determine in the correlation with the amount of degradation than total solar radiant dosage or duration of time. The comparison of UV radiant dosage from one location to another may be used to normalize degradation results.  
5.4 Measured UV irradiance data are scarce compared to total solar irradiance data. Many locations that monitor solar resource data only collect data for total solar radiation. This practice allows the user to estimate the amount of UV irradiance from the amount of total solar irradiance for any site.
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1.1 This practice describes methods to estimate the total solar ultraviolet irradiance on a horizontal surface as a function of Air Mass and geographic location.  
1.2 This practice provides a mathematical model for calculating Global Horizontal Ultraviolet irradiance (GHUV) from Global Horizontal Irradiance (GHI) data for a specific location.  
1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
4.1 This method is intended for use by laboratories performing calibration of a spectroradiometer for spectral irradiance measurements using a spectral irradiance standard with known spectral irradiance values and associated uncertainties traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance, known uncertainties and known measurement geometry.  
4.2 This method is generalized to allow for the use of different types of input optics provided that those input optics are suitable for the wavelength range and measurement geometry of the calibration.  
4.3 This method is generalized to allow for the use of different types of monochromators provided that they can be configured for a bandwidth, wavelength range, and throughput levels suitable for the calibration being performed.  
4.4 This method is generalized to allow for the use of different types of optical radiation detectors provided that the spectral response of the detector over the wavelength range of the calibration is appropriate to the signal levels produced by the monochromator.
SCOPE
1.1 This test method covers the calibration of spectroradiometers for the measurement of spectral irradiance using a standard of spectral irradiance that is traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance.  
1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input optics affects the overall uncertainty of the calibration.  
1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Parts of the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important that the choice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the method generally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers often suffer from stray light problems and have limited dynamic range. Diode array spectroradiometers are not recommended for use in the ultraviolet range unless these specific problems are addressed.  
1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectral irradiance must have known spectral irradiance values at given wavelengths for a specific input current and clearly defined measurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standard must be traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance. These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectral irradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, though other types of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200 to 4500 nm.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.2  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
4.1 This test method represents the preferable means for calibrating both narrow-band and broad-band ultraviolet radiometers. Calibration of narrow- and broad-band ultraviolet radiometers involving direct measurement of a standard source of spectral irradiance is an alternative method for calibrating ultraviolet radiometers. This approach is valid only if corrections for the spectral response of the instrument and the spectral mismatch between the calibration spectral distribution and the target spectral distribution can be computed. See Test Method E973 for a description of the spectral mismatch calculation.  
4.2 The accuracy of this calibration technique is dependent on the condition of the light source (for example, cloudy skies, polluted skies, aged lamps, defective luminaires, etc.), and on source alignment, source to receptor distance, and source power regulation.
Note 5: It is conceivable that a radiometer might be calibrated against a light source that represents an arbitrarily chosen degree of aging for its class in order to present to both the test and reference radiometers a spectrum that is most typical for the type.  
4.3 Spectroradiometric measurements performed using either an integrating sphere or a cosine receptor (such as a shaped PTFE3, or Al2O3 diffuser plate) provide a measurement of hemispherical spectral irradiance in the plane of the sphere's entrance port. As such, the aspect of the receptor plane relative to the reference light source must be defined (azimuth and tilt from the horizontal for solar measurements, normal incidence with respect to the beam component of sunlight, or normal incidence and the geometrical aspect with respect to an artificial light source, or array). It is important that the geometrical aspect between the plane of the spectroradiometer's source optics and that of the radiometer being calibrated be as nearly identical as possible.
Note 6: When measuring the hemispherical spectral energy distribution of an arra...
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1.1 This test method covers the calibration of ultraviolet light-measuring radiometers possessing either narrow- or broad-band spectral response distributions using either a scanning or a linear-diode-array spectroradiometer as the primary reference instrument. For transfer of calibration from radiometers calibrated by this test method to other instruments, Test Method E824 should be used.  
Note 1: Special precautions must be taken when a diode-array spectroradiometer is employed in the calibration of filter radiometers having spectral response distributions below 320-nm wavelength. Such precautions are described in detail in subsequent sections of this test method.  
1.2 This test method is limited to calibrations of radiometers against light sources that the radiometers will be used to measure during field use.  
Note 2: For example, an ultraviolet radiometer calibrated against natural sunlight cannot be employed to measure the total ultraviolet irradiance of a fluorescent ultraviolet lamp.  
1.3 Calibrations performed using this test method may be against natural sunlight, Xenon-arc burners, metal halide burners, tungsten and tungsten-halogen lamps, fluorescent lamps, etc.  
1.4 Radiometers that may be calibrated by this test method include narrow-, broad-, and wide-band ultraviolet radiometers, and narrow-, broad, and wide-band visible-region-only radiometers, or radiometers having wavelength response distributions that fall into both the ultraviolet and visible regions.  
Note 3: For purposes of this test method, narrow-band radiometers are those with Δλ ≤ 20 nm, broad-band radiometers are those with 20 nm ≤Δλ ≤ 70 nm, and wide-band radiometers are those with Δλ ≥ 70 nm.
Note 4: For purposes of this test method, the ultraviolet region is defined as the region from 285 to 400-nm wavelength, and the visible region is defined as the region from 400 to 750-nm wavelength. The ultraviolet region is further def...

SIGNIFICANCE AND USE
5.1 The methods described represent a means for calibration of field radiometers employing standard reference radiometers indoors. Other methods involve the natural sunlight outdoors under clear skies, and various combinations of reference radiometers. Outdoors, these methods are useful for cosine and azimuth correction analyses but may suffer from a lack of available clear skies, foreground view factor and directionality problems. Outdoor transfer of calibrations is covered by standards 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 the sensors are exposed.  
5.2.2 Extended sources (banks of lamps, or lamp(s) behind diffusing or “homogenizing” screens) to which the sensors are exposed.  
5.2.3 Various configurations of enclosures (usually spherical or hemispherical) with the interior walls illuminated indirectly with lamps. The sensors are exposed to the radiation emanating from the enclosure walls.  
5.3 Traceability of calibration for pyranometers is accomplished when employing the method using a reference global pyranometer that has been calibrated and is traceable to the World Radiometric Reference (WRR).4 For the purposes of this test method, traceability shall have been established if a parent instrument in the calibration chain can be traced to a reference pyrheliometer which has participated in an International Pyrheliometric Comparison (IPC) conducted at the World Radiation Center, (WRC), Davos, Switzerland.  
5.3.1 The reference global pyranometer (for example, one measuring hemispherical solar radiation at all wavelengths) shall have been calibrated by the shading-disk, component summation, or outdoor comparison method against one of the following instruments:
5.3.1.1 An absolute cavity pyrheliometer that participated in a World Meteorological Organization (WMO) sanctioned IPC's (and therefore possesses a WRR reduction factor).
5.3.1.2 An a...
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1.1 The method described in this standard applies to the indoor transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels.  
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed but is limited to radiometers having approximately 180° (2π Steradian), field angles.  
1.3 The calibration covered by this test method employs the use of artificial light sources (lamps).  
1.4 Calibrations of field radiometers are performed with sensors horizontal (at 0° tilt from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at horizontal tilt as employed in the transfer of calibration.  
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to outdoor calibration or intercomparisons.
Note 1: At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.  
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.  
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Method G167 and Test Method E816), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories (Standard G138).  
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibili...

SIGNIFICANCE AND USE
5.1 The methods described represent the preferable means for calibration of field radiometers employing standard reference radiometers. Other methods involve the employment of an optical bench and essentially a point source of artificial light. While these methods are useful for cosine and azimuth correction analyses, they suffer from foreground view factor and directionality problems. Transfer of calibration indoors using artificial sources is not covered by this test method.  
5.2 Traceability of calibration of global pyranometers is accomplished when employing the method using a reference global pyranometer that has been calibrated, and is traceable to the World Radiometric Reference (WRR). For the purposes of this test method, traceability shall have been established if a parent instrument in the calibration chain participated in an International Pyrheliometric Comparison (IPC) conducted at the World Radiation Center (WRC) in Davos, Switzerland. Traceability of calibration of narrow- and broad-band radiometers is accomplished when employing the method using a reference ultraviolet radiometer that has been calibrated and is traceable to the National Institute of Standards and Technology (NIST), or other national standards organizations. See Zerlaut4 for a discussion of the WRR, the IPC's and their results.  
5.2.1 The reference global pyranometer (for example, one measuring hemispherical solar radiation at all wavelengths) shall have been calibrated by the shading-disk or component summation method against one of the following instruments:
5.2.1.1 An absolute cavity pyrheliometer that participated in a WMO sanctioned IPC's (and therefore possesses a WRR reduction factor),
5.2.1.2 An absolute cavity radiometer that has been intercompared (in a local or regional comparison) with an absolute cavity pyrheliometer meeting the requirements given in 5.2.1.1.
5.2.1.3 A WMO First Class pyrheliometer that was calibrated by direct transfer from such an absolute cavi...
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1.1 The method described in this standard applies to the transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels. This standard has been harmonized with ISO 9847.  
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.  
1.3 The calibration covered by this test method employs the use of natural sunshine as the source.  
1.4 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at essentially the same tilt from horizontal as the tilt employed in the transfer of calibration.  
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.
Note 1: At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.  
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.  
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Test Methods G167 and E816), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories (Test Method G138).  
1.8 This standard does not purport to address all of the saf...

SIGNIFICANCE AND USE
5.1 The uncertainty in outdoor solar irradiance measurement has a significant impact on weathering and durability and the service lifetime of materials systems. Accurate solar irradiance measurement with known uncertainty will assist in determining the performance over time of component materials systems, including polymer encapsulants, mirrors, Photovoltaic modules, coatings, etc. Furthermore, uncertainty estimates in the radiometric data have a significant effect on the uncertainty of the expected electrical output of a solar energy installation.  
5.1.1 This influences the economic risk analysis of these systems. Solar irradiance data are widely used, and the economic importance of these data is rapidly growing. For proper risk analysis, a clear indication of measurement uncertainty should therefore be required.  
5.2 At present, the tendency is to refer to instrument datasheets only and take the instrument calibration uncertainty as the field measurement uncertainty. This leads to over-optimistic estimates. This guide provides a more realistic approach to this issue and in doing so will also assists users to make a choice as to the instrumentation that should be used and the measurement procedure that should be followed.  
5.3 The availability of the adjunct (ADJG021317)5 uncertainty spreadsheet calculator provides real world example, implementation of the GUM method, and assists to understand the contribution of each source of uncertainty to the overall uncertainty estimate. Thus, the spreadsheet assists users or manufacturers to seek methods to mitigate the uncertainty from the main uncertainty contributors to the overall uncertainty.
SCOPE
1.1 This guide provides guidance and recommended practices for evaluating uncertainties when calibrating and performing outdoor measurements with pyranometers and pyrheliometers used to measure total hemispherical- and direct solar irradiance. The approach follows the ISO procedure for evaluating uncertainty, the Guide to the Expression of Uncertainty in Measurement (GUM) JCGM 100:2008 and that of the joint ISO/ASTM standard ISO/ASTM 51707 Standard Guide for Estimating Uncertainties in Dosimetry for Radiation Processing, but provides explicit examples of calculations. It is up to the user to modify the guide described here to their specific application, based on measurement equation and known sources of uncertainties. Further, the commonly used concepts of precision and bias are not used in this document. This guide quantifies the uncertainty in measuring the total (all angles of incidence), broadband (all 52 wavelengths of light) irradiance experienced either indoors or outdoors.  
1.2 An interactive Excel spreadsheet is provided as adjunct, ADJG021317. The intent is to provide users real world examples and to illustrate the implementation of the GUM method.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight as in Test Methods E972, G130, and G207.  
5.2 The purpose of this test method is to foster greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
5.3 Changes in the optical properties of materials such as spectral reflectance, transmittance, or absorptance are often the measure of material stability or usefulness in various applications. Computation of the material responses to exposure to radiant sources mentioned above requires the integration of measured wavelength-dependent digital data, sometimes in conjunction with tabulated wavelength-dependent reference or comparison data.  
5.4 This test method specifies and describes the Modified Trapezoid Rule as a single reasonably accurate and easily implemented integration technique for computing approximations of spectral source and optical property integrals.  
5.5 The method includes a procedure for estimating the approximate absolute and relative (percent) error in the estimated spectral integrals.  
5.6 The method includes a procedure to construct data sets that match in spectral wavelength and spectral wavelength interval, which does not have to be uniform over the spectral range of interest. Uniform spectral intervals simplify some of the calculations, but are not required.
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1.1 This test method specifies a single relatively simple method to implement, common integration technique, the Modified Trapezoid Rule, to integrate digital or tabulated spectral data. The intent is to produce greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
1.2 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight. Changes in the spectrally dependent optical properties of materials, in combination with exposure source spectral data, are often used to evaluate the effect of exposure to radiant sources, develop activation spectra (Practice G178), and classify, evaluate, or rate sources with respect to reference or exposure source spectral distributions. Another important application is the integration of the original spectrally dependent optical properties of materials in combination with exposure source spectral data to determine the total energy absorbed by a material from various exposure sources.  
1.3 The data applications described in 1.2 often require the use of tabulated reference spectral distributions, digital spectral data produced by modern instrumentation, and the integrated version of that data, or combinations (primarily multiplication) of spectrally dependent data.  
1.4 Computation of the material responses to exposure to radiant sources mentioned above require the integration of measured wavelength dependent digital data, sometimes in conjunction with tabulated wavelength dependent reference or comparison data.  
1.5 The term “integration” in the previous sections refers to the numerical approximation to the true integral of continuous functions, represented by discrete, digital data. There are numerous mathematical techniques for performing numerical integration. Each method provides different levels of complexity, accuracy, ease of implementation and computational efficiency, an...

SIGNIFICANCE AND USE
5.1 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight as in Test Methods E972, G130, and G207.  
5.2 The purpose of this test method is to foster greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
5.3 Changes in the optical properties of materials such as spectral reflectance, transmittance, or absorptance are often the measure of material stability or usefulness in various applications. Computation of the material responses to exposure to radiant sources mentioned above requires the integration of measured wavelength-dependent digital data, sometimes in conjunction with tabulated wavelength-dependent reference or comparison data.  
5.4 This test method specifies and describes the Modified Trapezoid Rule as a single reasonably accurate and easily implemented integration technique for computing approximations of spectral source and optical property integrals.  
5.5 The method includes a procedure for estimating the approximate absolute and relative (percent) error in the estimated spectral integrals.  
5.6 The method includes a procedure to construct data sets that match in spectral wavelength and spectral wavelength interval, which does not have to be uniform over the spectral range of interest. Uniform spectral intervals simplify some of the calculations, but are not required.
SCOPE
1.1 This test method specifies a single relatively simple method to implement, common integration technique, the Modified Trapezoid Rule, to integrate digital or tabulated spectral data. The intent is to produce greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data.  
1.2 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight. Changes in the spectrally dependent optical properties of materials, in combination with exposure source spectral data, are often used to evaluate the effect of exposure to radiant sources, develop activation spectra (Practice G178), and classify, evaluate, or rate sources with respect to reference or exposure source spectral distributions. Another important application is the integration of the original spectrally dependent optical properties of materials in combination with exposure source spectral data to determine the total energy absorbed by a material from various exposure sources.  
1.3 The data applications described in 1.2 often require the use of tabulated reference spectral distributions, digital spectral data produced by modern instrumentation, and the integrated version of that data, or combinations (primarily multiplication) of spectrally dependent data.  
1.4 Computation of the material responses to exposure to radiant sources mentioned above require the integration of measured wavelength dependent digital data, sometimes in conjunction with tabulated wavelength dependent reference or comparison data.  
1.5 The term “integration” in the previous sections refers to the numerical approximation to the true integral of continuous functions, represented by discrete, digital data. There are numerous mathematical techniques for performing numerical integration. Each method provides different levels of complexity, accuracy, ease of implementation and computational efficiency, an...

SCOPE
1.1 This practice describes deployment conditions, maintenance requirements, verification procedures and calibration frequencies for use of pyranometers, pyrheliometers and UV radiometers in outdoor testing environments. This practice also discusses the conditions that dictate the level of accuracy required for instruments of different types.  
1.2 While both pyranometers and UV radiometers may be employed indoors to measure light radiation sources, the measurement of ultraviolet and light radiation in accelerated weathering enclosures using manufactured light sources generally requires specialized radiometric instruments. Use of radiometric instrumentation to measure laboratory light sources is covered in ISO 9370.
Note 1: An ASTM standard that is similar to ISO 9370 is under development and deals with the instrumental determination of irradiance and radiant exposure in weathering tests.  
1.3 The characterization of radiometers is outside the scope of the activities required of users of radiometers, as contemplated by this standard.

SIGNIFICANCE AND USE
4.1 The pyranometer is a radiometer designed to measure the sum of directly solar radiation and sky radiation in such proportions as solar altitude, atmospheric conditions and cloud cover may produce. When tilted to the equator, by an angle β, pyranometers measure only hemispherical radiation falling in the plane of the radiation receptor.  
4.2 This test method represents the only practical means for calibration of a reference pyranometer. While the sun-trackers, the shading disk, the number of instantaneous readings, and the electronic display equipment used will vary from laboratory to laboratory, the method provides for the minimum acceptable conditions, procedures and techniques required.  
4.3 While, in theory, the choice of tilt angle (β) is unlimited, in practice, satisfactory precision is achieved over a range of tilt angles close to the zenith angles used in the field.  
4.4 The at-tilt calibration as performed in the tilted position relates to a specific tilted position and in this position requires no tilt correction. However, a tilt correction may be required to relate the calibration to other orientations, including axis vertical.
Note 1: WMO High Quality pyranometers generally exhibit tilt errors of less than 0.5 %. Tilt error is the percentage deviation from the responsivity at 0° tilt (horizontal) due to change in tilt from 0° to 90° at 1000 W·m23.  
4.5 Traceability of calibrations to the World Radiometric Reference (WRR) is achieved through comparison to a reference absolute pyrheliometer that is itself traceable to the WRR through one of the following:  
4.5.1 One of the International Pyrheliometric Comparisons (IPC) held in Davos, Switzerland since 1980 (IPC IV). See Refs (3-7).  
4.5.2 Any like intercomparison held in the United States, Canada or Mexico and sanctioned by the World Meteorological Organization as a Regional Intercomparison of Absolute Cavity Pyrheliometers.  
4.5.3 Intercomparison with any absolute cavity pyrheliometer t...
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1.1 This test method covers an integration of previous Test Method E913 dealing with the calibration of pyranometers with axis vertical and previous Test Method E941 on calibration of pyranometers with axis tilted. This amalgamation of the two methods essentially harmonizes the methodology with ISO 9846.  
1.2 This test method is applicable to all pyranometers regardless of the radiation receptor employed, and is applicable to pyranometers in horizontal as well as tilted positions.  
1.3 This test method is mandatory for the calibration of all secondary standard pyranometers as defined by the World Meteorological Organization (WMO) and ISO 9060, and for any pyranometer used as a reference pyranometer in the transfer of calibration using Test Method E842.  
1.4 Two types of calibrations are covered: Type I calibrations employ a self-calibrating, absolute pyrheliometer, and Type II calibrations employ a secondary reference pyrheliometer as the reference standard (secondary reference pyrheliometers are defined by WMO and ISO 9060).  
1.5 Calibrations of reference pyranometers may be performed by a method that makes use of either an altazimuth or equatorial tracking mount in which the axis of the radiometer's radiation receptor is aligned with the sun during the shading disk test.  
1.6 The determination of the dependence of the calibration factor (calibration function) on variable parameters is called characterization. The characterization of pyranometers is not specifically covered by this method.  
1.7 This test method is applicable only to calibration procedures using the sun as the light source.  
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
4.1 Though the sun trackers employed, the number of instantaneous readings, and the data acquisition equipment used will vary from instrument to instrument and from laboratory to laboratory, this test method provides for the minimum acceptable conditions, procedures, and techniques required.  
4.2 While the greatest accuracy will be obtained when calibrating pyrheliometers with a self-calibrating absolute cavity pyrheliometer that has been demonstrated by intercomparison to be within ±0.5 % of the mean irradiance of a family of similar absolute instruments, acceptable accuracy can be achieved by careful attention to the requirements of this test method when transferring calibration from a secondary reference to a field pyrheliometer.  
4.3 By meeting the requirements of this test method, traceability of calibration to the World Radiometric Reference (WRR) can be achieved through one or more of the following recognized intercomparisons:  
4.3.1 International Pyrheliometric Comparison (IPC) VII, Davos, Switzerland, held in 1990, and every five years thereafter, and the PMO-2 absolute cavity pyrheliometer that is the primary reference instrument of WMO.6  
4.3.2 Any WMO-sanctioned intercomparison of self-calibrating absolute cavity pyrheliometers held in WMO Region IV (North and Central America).  
4.3.3 Any sanctioned or non-sanctioned intercomparison held in the United States the purpose of which is to transfer the WRR from the primary reference absolute cavity pyrheliometer maintained as the primary reference standard of the United States by the National Oceanic and Atmospheric Administration's Solar Radiation Facility in Boulder, CO.7  
4.3.4 Any future intercomparisons of comparable reference quality in which at least one self-calibrating absolute cavity pyrheliometer is present that participated in IPC VII or a subsequent IPC, and in which that pyrheliometer is treated as the intercomparison's reference instrument.  
4.3.5 Any of the absolute radiometers p...
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1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.  
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method prescribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.
Note 1: It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.  
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5 to 6°, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5°. Pyrheliometers with field angles greater than 6.5° shall not be designated as reference pyrheliometers.  
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5° or greater than 6.5°, it will be necessary to employ the procedure defined by Angstrom and Rodhe.2  
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 to 10 μm wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 to 4 μm wavelength.  
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.
Note 2: At a laboratory where calibration...

SIGNIFICANCE AND USE
4.1 This test method represents the preferable means for calibrating both narrow-band and broad-band ultraviolet radiometers. Calibration of narrow- and broad-band ultraviolet radiometers involving direct measurement of a standard source of spectral irradiance is an alternative method for calibrating ultraviolet radiometers. This approach is valid only if corrections for the spectral response of the instrument and the spectral mismatch between the calibration spectral distribution and the target spectral distribution can be computed. See Test Method  for a description of the spectral mismatch calculation.  
4.2 The accuracy of this calibration technique is dependent on the condition of the light source (for example, cloudy skies, polluted skies, aged lamps, defective luminaires, etc.), and on source alignment, source to receptor distance, and source power regulation.Note 5—It is conceivable that a radiometer might be calibrated against a light source that represents an arbitrarily chosen degree of aging for its class in order to present to both the test and reference radiometers a spectrum that is most typical for the type.  
4.3 Spectroradiometric measurements performed using either an integrating sphere or a cosine receptor (such as a shaped PTFE3, or Al2O3 diffuser plate) provide a measurement of hemispherical spectral irradiance in the plane of the sphere's entrance port. As such, the aspect of the receptor plane relative to the reference light source must be defined (azimuth and tilt from the horizontal for solar measurements, normal incidence with respect to the beam component of sunlight, or normal incidence and the geometrical aspect with respect to an artificial light source, or array). It is important that the geometrical aspect between the plane of the spectroradiometer's source optics and that of the radiometer being calibrated be as nearly identical as possible.Note 6—When measuring the hemispherical spectral energy distribution of an array of light s...
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1.1 This test method covers the calibration of ultraviolet light-measuring radiometers possessing either narrow- or broad-band spectral response distributions using either a scanning or a linear-diode-array spectroradiometer as the primary reference instrument. For transfer of calibration from radiometers calibrated by this test method to other instruments, Test Method E824 should be used. Note 1—Special precautions must be taken when a diode-array spectroradiometer is employed in the calibration of filter radiometers having spectral response distributions below 320-nm wavelength. Such precautions are described in detail in subsequent sections of this test method.  
1.2 This test method is limited to calibrations of radiometers against light sources that the radiometers will be used to measure during field use. Note 2—For example, an ultraviolet radiometer calibrated against natural sunlight cannot be employed to measure the total ultraviolet irradiance of a fluorescent ultraviolet lamp.  
1.3 Calibrations performed using this test method may be against natural sunlight, Xenon-arc burners, metal halide burners, tungsten and tungsten-halogen lamps, fluorescent lamps, etc.  
1.4 Radiometers that may be calibrated by this test method include narrow-, broad-, and wide-band ultraviolet radiometers, and narrow-, broad, and wide-band visible-region-only radiometers, or radiometers having wavelength response distributions that fall into both the ultraviolet and visible regions. Note 3—For purposes of this test method, narrow-band radiometers are those with Δλ ≤ 20 nm, broad-band radiometers are those with 20 nm ≤Δλ ≤ 70 nm, and wide-band radiometers are those with Δλ ≥ 70 nm.  
Note 4—For purposes of this test method, the ultraviolet region is defined as the region from 285 to 400-nm wavelength, and the visible region is defined as the region from 400 to 750-nm wavelength. The ultraviolet region is further defined as being e...

SIGNIFICANCE AND USE
4.1 This method is intended for use by laboratories performing calibration of a spectroradiometer for spectral irradiance measurements using a spectral irradiance standard with known spectral irradiance values and associated uncertainties traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance, known uncertainties and known measurement geometry.  
4.2 This method is generalized to allow for the use of different types of input optics provided that those input optics are suitable for the wavelength range and measurement geometry of the calibration.  
4.3 This method is generalized to allow for the use of different types of monochromators provided that they can be configured for a bandwidth, wavelength range, and throughput levels suitable for the calibration being performed.  
4.4 This method is generalized to allow for the use of different types of optical radiation detectors provided that the spectral response of the detector over the wavelength range of the calibration is appropriate to the signal levels produced by the monochromator.
SCOPE
1.1 This test method covers the calibration of spectroradiometers for the measurement of spectral irradiance using a standard of spectral irradiance that is traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance.  
1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input optics affects the overall uncertainty of the calibration.  
1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Parts of the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important that the choice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the method generally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers often suffer from stray light problems and have limited dynamic range. Diode array spectroradiometers are not recommended for use in the ultraviolet range unless these specific problems are addressed.  
1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectral irradiance must have known spectral irradiance values at given wavelengths for a specific input current and clearly defined measurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standard must be traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance. These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectral irradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, though other types of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200 to 4500 nm.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.2

SIGNIFICANCE AND USE
The methods described represent a means for calibration of field radiometers employing standard reference radiometers indoors. Other methods involve the natural sunlight outdoors under clear skies, and various combinations of reference radiometers. Outdoor these methods are useful for cosine and azimuth correction analyses, but may suffer from a lack of available clear skies, foreground view factor and directionality problems. Outdoor transfer of calibrations is covered by standards , , and .
Several configurations of artificial sources are possible, including:
Point sources (lamps) at a distance, to which the sensors are exposed
Extended sources (banks of lamps, or lamp(s) behind diffusing or “homogenizing” screens) to which the sensors are exposed
Various configurations of enclosures (usually spherical or hemispherical) with the interior walls illuminated indirectly with lamps. The sensors are exposed to the radiation emanating from the enclosure walls.
Traceability of calibration for pyranometers is accomplished when employing the method using a reference global pyranometer that has been calibrated, and is traceable to the World Radiometric Reference (WRR) . For the purposes of this test method, traceability shall have been established if a parent instrument in the calibration chain can be traced to a reference pyrheliometer which has participated in an International Pyrheliometric Comparison (IPC) conducted at the World Radiation Center, (WRC), Davos, Switzerland.
The reference global pyranometer (for example, one measuring hemispherical solar radiation at all wavelengths) shall have been calibrated by the shading-disk, component summation, or outdoor comparison method against one of the following instruments:
An absolute cavity pyrheliometer that participated in a World Meteorological Organization (WMO) sanctioned IPC's (and therefore possesses a WRR reduction factor).
An absolute cavity radiometer that has been intercompared (in a local or regi...
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1.1 The method described in this standard applies to the indoor transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels.
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.
1.3 The calibration covered by this test method employs the use of artificial light sources (lamps).
1.4 Calibrations of field radiometers are performed with sensors horizontal (at 0° tilt from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at horizontal tilt as employed in the transfer of calibration.
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to outdoor calibration or intercomparisons.
Note 1—At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Method and Test Method ), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories (Standard ).
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of t...

SCOPE
1.1 This practice describes deployment conditions, maintenance requirements, verification procedures and calibration frequencies for use of pyranometers, pyrheliometers and UV radiometers in outdoor testing environments. This practice also discusses the conditions that dictate the level of accuracy required for instruments of different classes.
1.2 While both pyranometers and UV radiometers may be employed indoors to measure light radiation sources, the measurement of ultraviolet and light radiation in accelerated weathering enclosures using manufactured light sources generally requires specialized radiometric instruments. Use of radiometric instrumentation to measure laboratory light sources is covered in ISO 9370.
Note 1—An ASTM standard that is similar to ISO 9370 is under development and deals with the instrumental determination of irradiance and radiant exposure in weathering tests.
1.3 The characterization of radiometers is outside the scope of the activities required of users of radiometers, as contemplated by this standard.

SIGNIFICANCE AND USE
The methods described represent the preferable means for calibration of field radiometers employing standard reference radiometers. Other methods involve the employment of an optical bench and essentially a point source of artificial light. While these methods are useful for cosine and azimuth correction analyses, they suffer from foreground view factor and directionality problems. Transfer of calibration indoors using artificial sources is not covered by this test method.
Traceability of calibration of global pyranometers is accomplished when employing the method using a reference global pyranometer that has been calibrated, and is traceable to the World Radiometric Reference (WRR). For the purposes of this test method, traceability shall have been established if a parent instrument in the calibration chain participated in an International Pyrheliometric Comparison (IPC) conducted at the World Radiation Center (WRC) in Davos, Switzerland. Traceability of calibration of narrow- and broad-band radiometers is accomplished when employing the method using a reference ultraviolet radiometer that has been calibrated and is traceable to the National Institute of Standards and Technology (NIST), or other national standards organizations. See Zerlaut for a discussion of the WRR, the IPC's and their results.
The reference global pyranometer (for example, one measuring hemispherical solar radiation at all wavelengths) shall have been calibrated by the shading-disk or component summation method against one of the following instruments:
An absolute cavity pyrheliometer that participated in a WMO sanctioned IPC's (and therefore possesses a WRR reduction factor),
An absolute cavity radiometer that has been intercompared (in a local or regional comparison) with an absolute cavity pyrheliometer meeting the requirements given in 5.2.1.1.
A WMO First Class pyrheliometer that was calibrated by direct transfer from such an absolute cavity.
Alternatively, the reference pyrano...
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1.1 The method described in this standard applies to the transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels. This standard has been harmonized with ISO 9847.
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.
1.3 The calibration covered by this test method employs the use of natural sunshine as the source.
1.4 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at essentially the same tilt from horizontal as the tilt employed in the transfer of calibration.
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.
Note 1—At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Test Methods G167 and E816), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories (Test Method G138).
1.8 This standard does not purport to address all of the safety con...

SIGNIFICANCE AND USE
The pyranometer is a radiometer designed to measure the sum of directly solar radiation and sky radiation in such proportions as solar altitude, atmospheric conditions and cloud cover may produce. When tilted to the equator, by an angle β, pyranometers measure only hemispherical radiation falling in the plane of the radiation receptor.
This test method represents the only practical means for calibration of a reference pyranometer. While the sun-trackers, the shading disk, the number of instantaneous readings, and the electronic display equipment used will vary from laboratory to laboratory, the method provides for the minimum acceptable conditions, procedures and techniques required.
While, in theory, the choice of tilt angle (β) is unlimited, in practice, satisfactory precision is achieved over a range of tilt angles close to the zenith angles used in the field.
The at-tilt calibration as performed in the tilted position relates to a specific tilted position and in this position requires no tilt correction. However, a tilt correction may be required to relate the calibration to other orientations, including axis vertical.
Note 1—WMO Fist Class pyranometers, or better, generally exhibit tilt errors of less than 1 % to tilts of 50° from the horizontal.
Traceability of calibrations to the World Radiometric Reference (WRR) is achieved through comparison to a reference absolute pyrheliometer that is itself traceable to the WRR through one of the following:
One of the International Pyrheliometric Comparisons (IPC) held in Davos, Switzerland since 1980 (IPC IV). See Refs (3-7).
Any like intercomparison held in the United States, Canada or Mexico and sanctioned by the World Meteorological Organization as a Regional Intercomparison of Absolute Cavity Pyrheliometers.
Intercomparison with any absolute cavity pyrheliometer that has participated in either and IPC or a WMO-sanctioned intercomparison within the past five years and which was found to be within ±0....
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1.1 This test method covers an integration of previous Test Method E913 dealing with the calibration of pyranometers with axis vertical and previous Test Method E941 on calibration of pyranometers with axis tilted. This amalgamation of the two methods essentially harmonizes the methodology with ISO 9846.
1.2 This test method is applicable to all pyranometers regardless of the radiation receptor employed, and is applicable to pyranometers in horizontal as well as tilted positions.
1.3 This test method is mandatory for the calibration of all secondary standard pyranometers as defined by the World Meteorological Organization (WMO) and ISO 9060, and for any pyranometer used as a reference pyranometer in the transfer of calibration using Test Method E842.
1.4 Two types of calibrations are covered: Type I calibrations employ a self-calibrating, absolute pyrheliometer, and Type II calibrations employ a secondary reference pyrheliometer as the reference standard (secondary reference pyrheliometers are defined by WMO and ISO 9060).
1.5 Calibrations of reference pyranometers may be performed by a method that makes use of either an altazimuth or equatorial tracking mount in which the axis of the radiometer's radiation receptor is aligned with the sun during the shading disk test.
1.6 The determination of the dependence of the calibration factor (calibration function) on variable parameters is called characterization. The characterization of pyranometers is not specifically covered by this method.
1.7 This test method is applicable only to calibration procedures using the sun as the light source.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
Though the sun trackers employed, the number of instantaneous readings, and the data acquisition equipment used will vary from instrument to instrument and from laboratory to laboratory, this test method provides for the minimum acceptable conditions, procedures, and techniques required.
While the greatest accuracy will be obtained when calibrating pyrheliometers with a self-calibrating absolute cavity pyrheliometer that has been demonstrated by intercomparison to be within ±0.5 % of the mean irradiance of a family of similar absolute instruments, acceptable accuracy can be achieved by careful attention to the requirements of this test method when transferring calibration from a secondary reference to a field pyrheliometer.
By meeting the requirements of this test method, traceability of calibration to the World Radiometric Reference (WRR) can be achieved through one or more of the following recognized intercomparisons:
International Pyrheliometric Comparison (IPC) VII, Davos, Switzerland, held in 1990, and every five years thereafter, and the PMO-2 absolute cavity pyrheliometer that is the primary reference instrument of WMO.  
Any WMO-sanctioned intercomparison of self-calibrating absolute cavity pyrheliometers held in WMO Region IV (North and Central America).
Any sanctioned or non-sanctioned intercomparison held in the United States the purpose of which is to transfer the WRR from the primary reference absolute cavity pyrheliometer maintained as the primary reference standard of the United States by the National Oceanic and Atmospheric Administration's Solar Radiation Facility in Boulder, CO.  
Any future intercomparisons of comparable reference quality in which at least one self-calibrating absolute cavity pyrheliometer is present that participated in IPC VII or a subsequent IPC, and in which that pyrheliometer is treated as the intercomparison's reference instrument.
Any of the absolute radiometers participating in the above intercomparisons and be...
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1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method proscribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.
Note 1—It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5 to 6°, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5°. Pyrheliometers with field angles greater than 6.5° shall not be designated as reference pyrheliometers.
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5° or greater than 6.5°, it will be necessary to employ the procedure defined by Angstrom and Rodhe.  
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 to 10 μm wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 to 4 μm wavelength.
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.
Note 2—At a laboratory where calibrations are...

SIGNIFICANCE AND USE
Absorptance, reflectance, and transmittance of solar energy are important factors in material degradation studies, solar thermal system performance, solar photovoltaic system performance, biological studies, and solar simulation activities. These optical properties are normally functions of wavelength, which require the spectral distribution of the solar flux be known before the solar-weighted property can be calculated. To compare the relative performance of competitive products, or to compare the performance of products before and after being subjected to weathering or other exposure conditions, a reference standard solar spectral distribution is desirable.
These tables provide appropriate standard spectral irradiance distributions for determining the relative optical performance of materials, solar thermal, solar photovoltaic, and other systems. The tables may be used to evaluate components and materials for the purpose of solar simulation where either the direct or the hemispherical (that is, direct beam plus diffuse sky) spectral solar irradiance is desired. However, these tables are not intended to be used as a benchmark for ultraviolet radiation used in indoor exposure testing of materials using manufactured light sources.
The total integrated irradiances for the direct and hemispherical tilted spectra are 900.1 W·m-2 and 1000.4 W·m-2, respectively. Note that, in PV applications, no amplitude adjustments are required to match standard reporting condition irradiances of 1000 W·m-2 for hemispherical irradiance.
Previously defined global hemispherical reference spectrum (G159) for a sun-facing 37°-tilted surface served well to meet the needs of the flat plate photovoltaic research, development, and industrial community. Investigation of prevailing conditions and measured spectra shows that this global hemispherical reference spectrum can be attained in practice under a variety of conditions, and that these conditions can be interpreted as representative fo...
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1.1 These tables contain terrestrial solar spectral irradiance distributions for use in terrestrial applications that require a standard reference spectral irradiance for hemispherical solar irradiance (consisting of both direct and diffuse components) incident on a sun-facing, 37° tilted surface or the direct normal spectral irradiance. The data contained in these tables reflect reference spectra with uniform wavelength interval (0.5 nanometer (nm) below 400 nm, 1 nm between 400 and 1700 nm, an intermediate wavelength at 1702 nm, and 5 nm intervals from 1705 to 4000 nm). The data tables represent reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production, as well as weathering and durability exposure applications.
1.2 The 37° slope of the sun-facing tilted surface was chosen to represent the average latitude of the 48 contiguous United States. A wide variety of orientations is possible for exposed surfaces. The availability of the SMARTS model (as an adjunct, ADJG173CD ) to this standard) used to generate the standard spectra allows users to evaluate differences relative to the surface specified here.
1.3 The air mass and atmospheric extinction parameters are chosen to provide (1) historical continuity with respect to previous standard spectra, (2) reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production or weathering and durability exposure, based upon modern broadband solar radiation data, atmospheric profiles, and improved knowledge of aerosol optical depth profiles. In nature, an extremely large range of atmospheric conditions can be encountered even under cloudless skies. Considerable departure from the reference spectra may be observed depending on time of day, geographical location, and changing atmospheric conditions. The availability of the SMARTS model (as an adjunct (ADJG173CD )to this standard) used to generate the standard spectra a...

SIGNIFICANCE AND USE
This standard does not purport to address the mean level of solar ultraviolet spectral irradiance to which materials will be subjected during their useful life. The spectral irradiance distributions have been chosen to represent a reasonable upper limit for natural solar ultraviolet radiation that ought to be considered when evaluating the behavior of materials under various exposure conditions.
Absorptance, reflectance, and transmittance of solar energy are important factors in material degradation studies. These properties are normally functions of wavelength, which require that the spectral distribution of the solar flux be known before the solar-weighted property can be calculated.
The interpretation of the behavior of materials exposed to either natural solar radiation or ultraviolet radiation from artificial light sources requires an understanding of the spectral energy distribution employed. To compare the relative performance of competitive products, or to compare the performance of products before and after being subjected to weathering or other exposure conditions, a reference standard solar spectral distribution is desirable.
A plot of the SMARTS2 model output for the reference hemispherical UV radiation on a 37° south facing tilted surface is shown in Fig. 1. The input needed by SMARTS2 to generate the spectrum for the prescribed conditions are shown in Table 2.
SMARTS2 Version 2.9.2 is required to generate AM 1.05 UV reference spectra.
The availability of the adjunct standard computer software (ADJG0173CD ) for SMARTS2 allows one to (1) reproduce the reference spectra, using the above input parameters; (2) compute test spectra to attempt to match measured data at a specified FWHM, and evaluate atmospheric conditions; and (3) compute test spectra representing specific conditions for analysis vis-à-vis any one or all of the reference spectra.
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1.1 The table provides a standard ultraviolet spectral irradiance distribution that maybe employed as a guide against which manufactured ultraviolet light sources may be judged when applied to indoor exposure testing. The table provides a reference for comparison with natural sunlight ultraviolet spectral data. The ultraviolet reference spectral irradiance is providded for the wavelength range from 280 to 400 nm. The wavelength region selected is comprised of the UV-A spectral region from 320 to 400 nm and the UV-B region from 280 to 320 nm.
1.2 The table defines a single ultraviolet solar spectral irradiance distribution:
1.2.1 Total hemispherical ultraviolet solar spectral irradiance (consisting of combined direct and diffuse components) incident on a sun-facing, 37° tilted surface in the wavelength region from 280 to 400 nm for air mass 1.05, at an elevation of 2 km (2000 m) above sea level for the United States Standard Atmosphere profile for 1976 (USSA 1976), excepting for the ozone content which is specified as 0.30 atmosphere-centimeters (atm-cm) equivalent thichkness.
1.3 The data contained in these tables were generated using the SMARTS2 Version 2.9.2 atmospheric transmission model developed by Gueymard (1,2).
1.4 The climatic, atmospheric and geometric parameters selected reflect the conditions to provide a realistic maximum ultraviolet exposure under representative clear sky conditions.
1.5 The availability of the SMARTS2 model (as an adjunct (ADJG0173CD )to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.

SIGNIFICANCE AND USE
This standard does not purport to address the mean spectral irradiance incident on tilted or vertical fenestration or building-integrated systems over a day, a season, or a year. The spectral irradiance distributions have been chosen to represent a reasonable near-upper limit for solar radiation when these systems are exposed to clear-sky conditions similar to those used to calculate solar heat loads of buildings. The diffuse spectral irradiance distributions can also be used to represent conditions when these systems are shaded from the direct sun.
Absorptance, reflectance, and transmittance of solar radiation are important factors in studies of light transmission through semi-transparent plates. These properties are normally functions of wavelength, which require that the spectral distribution of the solar flux be known before the solar-weighted property can be calculated.
To compare the relative performance of competitive products by computerized simulations, or to compare the performance of products subjected to experimental tests in laboratory conditions, a reference standard solar spectral distribution for both direct and diffuse irradiance is desirable.
The table provides appropriate standard spectral irradiance distributions for determining the relative optical performance of semi-transparent materials and other systems. The table may be used to evaluate components and materials for the purpose of solar simulation where the direct and the diffuse spectral solar irradiances are needed separately.
The selected air mass value of 1.5 for a plane-parallel atmosphere above a flat earth corresponds to a zenith angle of 48.19°. The SMARTS2 computation of air mass accounts for atmospheric curvature and the vertical density profile of molecules, which results in a solar zenith angle of 48.236°, or an equivalent plane-parallel-atmosphere air mass of 1.50136. The angle of incidence computed by SMARTS for the direct beam irradiance incident on a 20°-tilted plane ...
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1.1 This table provides terrestrial solar spectral irradiance distributions that may be employed as weighting functions to (1) calculate the broadband solar or light transmittance of fenestration from its spectral properties; or (2) evaluate the performance of building-integrated technologies such as photovoltaic electricity generators. Most of these systems are installed on vertical walls, but some are also installed on pitched roofs or on other tilted structures, such as sunspaces. Glazing transmittance calculations or measurements require information on both the direct and diffuse components of irradiance. The table provides separate information for direct and diffuse irradiance, and for two different tilt angles, 20° and 90° relative to the horizontal. All distributions are provided at 2002 wavelengths within the spectral range 280–4000 nm. The data contained in this table reflect reference spectra with uniform wavelength interval (0.5 nanometer (nm) below 400 nm, 1 nm between 400 and 1700 nm, an intermediate wavelength at 1702 nm, and 5 nm intervals from 1705 to 4000 nm). The data table represents reasonable cloudless atmospheric conditions favorable for the computerized simulation, comparative rating, or experimental testing of fenestration systems.
1.2 The data contained in this table were generated using the SMARTS version 2.9.2 atmospheric transmission model developed by Gueymard (1, 2).
1.3 The selection of the SMARTS radiative model to generate the spectral distributions is chosen for compatibility with previous standards (ASTM G 173 and G 177). The atmospheric and climatic conditions are identical to those in ASTM G 173. The environmental conditions are also identical, with only one exception (see sections 4.3 and X1.2).
1.4 The table defines four solar spectral irradiance distributions:
1.4.1 Separate direct and diffuse solar spectral irradiance incident on a sun-facing, 20° tilted surface in the wav...

SIGNIFICANCE AND USE
This method is intended for use by laboratories performing calibration of a spectroradiometer for spectral irradiance measurements using a spectral irradiance standard of known spectral irradiance values traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance, known uncertainties and known measurement geometry.
This method is generalized to allow for the use of different types of input optics provided that those input optics are suitable for the wavelength range and measurement geometry of the calibration.
This method is generalized to allow for the use of different types of monochromators provided that they can be configured for a bandwidth, wavelength range, and throughput levels suitable for the calibration being performed.
This method is generalized to allow for the use of different types of optical radiation detectors provided that the spectral response of the detector over the wavelength range of the calibration is appropriate to the signal levels produced by the monochromator.
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1.1 This test method covers the calibration of spectroradiometers for the measurement of spectral irradiance using a standard of spectral irradiance that is traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance.
1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input optics affects the overall uncertainty of the calibration.
1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Parts of the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important that the choice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the method generally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers often suffer from stray light problems and have limited dynamic range. Diode array spectroradiometers are not recommended for use in the ultraviolet range unless these specific problems are addressed.
1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectral irradiance must have known spectral irradiance values at given wavelengths for a specific input current and clearly defined measurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standard must be traceable to a national metrological laboratory that has participated in intercomparisons of standards of spectral irradiance. These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectral irradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, though other types of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200 to 4500 nm.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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1.1 This test method covers the calibration of ultraviolet light-measuring radiometers possessing either narrow- or broad-band spectral response distributions using either a scanning or a linear-diode-array spectroradiometer as the primary reference instrument. For transfer of calibration from radiometers calibrated by this test method to other instruments, Test Method E 824 should be used. Note 1 Special precautions must be taken when a diode-array spectroradiometer is employed in the calibration of filter radiometers having spectral response distributions below 320-nm wavelength. Such precautions are described in detail in subsequent sections of this test method.
1.2 This test method is limited to calibrations of radiometers against light sources that the radiometers will be used to measure during field use. Note 2 For example, an ultraviolet radiometer calibrated against natural sunlight cannot be employed to measure the total ultraviolet irradiance of a fluorescent ultraviolet lamp.
1.3 Calibrations performed using this test method may be against natural sunlight, Xenon-arc burners, metal halide burners, tungsten and tungsten-halogen lamps, fluorescent lamps, etc.
1.4 Radiometers that may be calibrated by this test method include narrow-, broad-, and wide-band ultraviolet radiometers, and narrow-, broad, and wide-band visible-region-only radiometers, or radiometers having wavelength response distributions that fall into both the ultraviolet and visible regions. Note 3 For purposes of this test method, narrow-band radiometers are those with 20 nm, broad-band radiometers are those with 20 nm 70 nm, and wide-band radiometers are those with 70 nm.
Note 4
For purposes of this test method, the ultraviolet region is defined as the region from 285 to 400-nm wavelength, and the visible region is defined as the region from 400 to 750-nm wavelength. The ultraviolet region is further defined as being either UV-A with radiation of wavelengths from 315 to 400 nm, or UV-B with radiation from 285 to 315-nm wavelength.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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1.1 This test method covers an integration of previous Test Method E 913 dealing with the calibration of pyranometers with axis vertical and previous Test Method E 941 on calibration of pyranometers with axis tilted. This amalgamation of the two methods essentially harmonizes the methodology with ISO 9846.
1.2 This test method is applicable to all pyranometers regardless of the radiation receptor employed, and is applicable to pyranometers in horizontal as well as tilted positions.
1.3 This test method is mandatory for the calibration of all secondary standard pyranometers as defined by the World Meteorological Organization (WMO) and ISO 9060, and for any pyranometer used as a reference pyranometer in the transfer of calibration using Test Method E 842.
1.4 Two types of calibrations are covered: Type I calibrations employ a self-calibrating, absolute pyrheliometer, and Type II calibrations employ a secondary reference pyrheliometer as the reference standard (secondary reference pyrheliometers are defined by WMO and ISO 9060).
1.5 Calibrations of reference pyranometers may be performed by a method that makes use of either an altazimuth or equatorial tracking mount in which the axis of the radiometer's radiation receptor is aligned with the sun during the shading disk test.
1.6 The determination of the dependence of the calibration factor (calibration function) on variable parameters is called characterization. The characterization of pyranometers is not specifically covered by this method.
1.7 This test method is applicable only to calibration procedures using the sun as the light source.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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1.1 The method described in this standard applies to the transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels. This standard has been harmonized with ISO 9847.
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.
1.3 The calibration covered by this test method employs the use of natural sunshine as the source.
1.4 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at essentially the same tilt from horizontal as the tilt employed in the transfer of calibration.
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.
Note 1—At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Method E 913 and Test Method E 941), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method proscribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.Note 1
It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5 to 6, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5. Pyrheliometers with field angles greater than 6.5 shall not be designated as reference pyrheliometers.
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5 or greater than 6.5, it will be necessary to employ the procedure defined by Angstrom and Rodhe.
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 to 10-m wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 to 4-m wavelength.
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.Note 2
At a laboratory where calibrations are performed regularly, it is advisable to maintain a group of two or three secondary reference pyrheliometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference pyrheliometer.
1.7 This test method is applicable to calibration procedures using natural sunshine only.

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1.1 This practice describes deployment conditions, maintenance requirements, verification procedures and calibration frequencies for use of pyranometers, pyrheliometers and UV radiometers in outdoor testing environments. This practice also discusses the conditions that dictate the level of accuracy required for instruments of different classes.
1.2 While both pyranometers and UV radiometers may be employed indoors to measure light radiation sources, the measurement of ultraviolet and light radiation in accelerated weathering enclosures using manufactured light sources generally requires specialized radiometric instruments. Use of radiometric instrumentation to measure laboratory light sources is covered in ISO 9370.Note 1
An ASTM standard that is similar to ISO 9370 is under development and deals with the instrumental determination of irradiance and radiant exposure in weathering tests.
1.3 The characterization of radiometers is outside the scope of the activities required of users of radiometers, as contemplated by this standard.

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1.1 The table provides a standard ultraviolet spectral irradiance distribution that maybe employed as a guide against which manufactured ultraviolet light sources may be judged when applied to indoor exposure testing. The table provides a reference for comparison with natural sunlight ultraviolet spectral data. The ultraviolet reference spectral irradiance is providded for the wavelength range from 280 to 400 nm. The wavelength region selected is comprised of the UV-A spectral region from 320 to 400 nm and the UV-B region from 280 to 320 nm.
1.2 The table defines a single ultraviolet solar spectral irradiance distribution:
1.2.1 Total hemispherical ultraviolet solar spectral irradiance (consisting of combined direct and diffuse components) incident on a sun-facing, 37 tilted surface in the wavelength region from 280 to 400 nm for air mass 1.05, at an elevation of 2 km (2000 m) above sea level for the United States Standard Atmosphere profile for 1976 (USSA 1976), excepting for the ozone content which is specified as 0.30 atmosphere-centimeters (atm-cm) equivalent thichkness.
1.3 The data contained in these tables were generated using the SMARTS2 Version 2.9.2 atmospheric transmission model developed by Gueymard (1,2).
1.4 The climatic, atmospheric and geometric parameters selected reflect the conditions to provide a realistic maximum ultraviolet exposure under representative clear sky conditions.
1.5 The availability of the SMARTS2 model (as an adjunct to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.

SCOPE
1.1 This test method covers the calibration of spectroradiometers for the measurement of spectral irradiance using a standard of spectral irradiance that is traceable to NIST.
Note 1—Although NIST is referenced throughout this standard, it should be assumed that other internationally recognized standards laboratories may be substituted.
1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input optics affects the overall uncertainty of the calibration.
1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Parts of the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important that the choice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the method generally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers often suffer from stray light problems and have limited dynamic range. Diode array spectroradiometers are not recommended for use in the ultraviolet range unless these specific problems are addressed.
1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectral irradiance must have known spectral irradiance values at given wavelengths for a specific input current and clearly defined measurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standard must be traceable to NIST. These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectral irradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, though other types of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200 to 4500 nm.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 These tables contain terrestrial solar spectral irradiance distributions for use in terrestrial applications that require a standard reference spectral irradiance for hemispherical solar irradiance (consisting of both direct and diffuse components) incident on a sun-facing, 37° tilted surface or the direct normal spectral irradiance. The data contained in these tables reflect reference spectra with uniform wavelength interval (0.5 nanometer (nm) below 400 nm, 1 nm between 400 and 1700 nm, an intermediate wavelength at 1702 nm, and 5 nm intervals from 1705 to 4000 nm). The data tables represent reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production, as well as weathering and durability exposure applications.
1.2 The 37 slope of the sun-facing tilted surface was chosen to represent the average latitude of the 48 contiguous United States. A wide variety of orientations is possible for exposed surfaces. The availability of the SMARTS model (as an adjunct to this standard) used to generate the standard spectra allows users to evaluate differences relative to the surface specified here.
1.3 The air mass and atmospheric extinction parameters are chosen to provide (1) historical continuity with respect to previous standard spectra, (2) reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production or weathering and durability exposure, based upon modern broadband solar radiation data, atmospheric profiles, and improved knowledge of aerosol optical depth profiles. In nature, an extremely large range of atmospheric conditions can be encountered even under cloudless skies. Considerable departure from the reference spectra may be observed depending on time of day, geographical location, and changing atmospheric conditions. The availability of the SMARTS model (as an adjunct to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.

SCOPE
1.1 These tables contain terrestrial solar spectral irradiance distributions for use in terrestrial applications that require a standard reference spectral irradiance for hemispherical solar irradiance (consisting of both direct and diffuse components) incident on a sun-facing, 37° tilted surface or the direct normal spectral irradiance. The data contained in these tables reflect reference spectra with uniform wavelength interval (0.5 nanometer (nm) below 400 nm, 1 nm between 400 and 1700 nm, an intermediate wavelength at 1702 nm, and 5 nm intervals from 1705 to 4000 nm). The data tables represent reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production, as well as weathering and durability exposure applications.
1.2 The 37 slope of the sun-facing tilted surface was chosen to represent the average latitude of the 48 contiguous United States. A wide variety of orientations is possible for exposed surfaces. The availability of the SMARTS model (as an adjunct to this standard) used to generate the standard spectra allows users to evaluate differences relative to the surface specified here.
1.3 The air mass and atmospheric extinction parameters are chosen to provide (1) historical continuity with respect to previous standard spectra, (2) reasonable cloudless atmospheric conditions favorable for photovoltaic (PV) energy production or weathering and durability exposure, based upon modern broadband solar radiation data, atmospheric profiles, and improved knowledge of aerosol optical depth profiles. In nature, an extremely large range of atmospheric conditions can be encountered even under cloudless skies. Considerable departure from the reference spectra may be observed depending on time of day, geographical location, and changing atmospheric conditions. The availability of the SMARTS model (as an adjunct to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.

SCOPE
1.1 This test method covers an integration of Test Method E 913 dealing with the calibration of pyranometers with axis vertical and Test Method E 941 on calibration of pyranometers with axis tilted. This amalgamation of the two methods essentially harmonizes the methodology with ISO 9846.
1.2 This test method is applicable to all pyranometers regardless of the radiation receptor employed, and is applicable to pyranometers in horizontal as well as tilted positions.
1.3 This test method is mandatory for the calibration of all secondary standard pyranometers as defined by the World Meteorological Organization (WMO) and ISO 9060, and for any pyranometer used as a reference pyranometer in the transfer of calibration using Test Method E 842.
1.4 Two types of calibrations are covered: Type I calibrations employ a self-calibrating, absolute pyrheliometer, and Type II calibrations employ a secondary reference pyrheliometer as the reference standard (secondary reference pyrheliometers are defined by WMO and ISO 9060).
1.5 Calibrations of reference pyranometers may be performed by a method that makes use of either an altazimuth or equitorial tracking mount in which the axis of the radiometer's radiation receptor is aligned with the sun during the shading disk test.
1.6 The determination of the dependence of the calibration factor (calibration function) on variable parameters is called characterization. The characterization of pyranometers is not specifically covered by this method.
1.7 This test method is applicable only to calibration procedures using the sun as the light source.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This test method covers the calibration of spectroradiometers for the measurement of spectral irradiance using a standard of special irradiance that is traceable to NIST.  
Note- Although NIST is referenced throughout this standard, it should be assumed that other internationally recognized standards laboratories may be substituted.  
1.2 This method is not limited by the input optics of the spectroradiometric system. However, choice of input optics affects the overall uncertainty of the calibration.  
1.3 This method is not limited by the type of monochromator or optical detector used in the spectroradiometer system. Parts of the method may not apply to determine which parts apply to the specific spectroradiometer being used. It is important that the choice of monochromator and detector be appropriate for the wavelength range of interest for the calibration. Though the method generally applies to photodiode array detector based systems, the user should note that these types of spectroradiometers often suffer from stray light problems and have limited dynamic range. Diode array spectroradiometers are not recommended for use in the ultraviolet range unless these specific problems are addressed.  
1.4 The calibration described in this method employs the use of a standard of spectral irradiance. The standard of spectral irradiance values at given wavelengths for a specific input current and clearly defined measurement geometry. Uncertainties must also be known for the spectral irradiance values. The values assigned to this standard must be traceable to NIST. These standards may be obtained from a number of national standards laboratories and commercial laboratories. The spectral irradiance standards consist mainly of tungsten halogen lamps with coiled filaments enclosed in a quartz envelope, though other types of lamps are used. Standards can be obtained with calibration values covering all or part of the wavelength range from 200 to 4500 nm.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method proscribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.
Note 1—It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5 to 6°, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5°. Pyrheliometers with field angles greater than 6.5° shall not be designated as reference pyrheliometers.
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5° or greater than 6.5°, it will be necessary to employ the procedure defined by Angstrom and Rodhe.
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 to 10-μm wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 to 4-μm wavelength.
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.
Note 2—At a laboratory where calibrations are performed regularly, it is advisable to maintain a group of two or three secondary reference pyrheliometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference pyrheliometer.
1.7 This test method is applicable to calibration procedures using natural sunshine only.

SCOPE
1.1 This test method covers the calibration of ultraviolet light-measuring radiometers possessing either narrow- or broad-band spectral response distributions using either a scanning or a linear-diode-array spectroradiometer as the primary reference instrument. For transfer of calibration from radiometers calibrated by this test method to other instruments, Test Method E 824 should be used.
Note 1—Special precautions must be taken when a diode-array spectroradiometer is employed in the calibration of filter radiometers having spectral response distributions below 320-nm wavelength. Such precautions are described in detail in subsequent sections of this test method.
1.2 This test method is limited to calibrations of radiometers against light sources that the radiometers will be used to measure during field use.
Note 2—For example, an ultraviolet radiometer calibrated against natural sunlight cannot be employed to measure the total ultraviolet irradiance of a fluorescent ultraviolet lamp.
1.3 Calibrations performed using this test method may be against natural sunlight, Xenon-arc burners, metal halide burners, tungsten and tungsten-halogen lamps, fluorescent lamps, etc.
1.4 Radiometers that may be calibrated by this test method include narrow-, broad-, and wide-band ultraviolet radiometers, and narrow-, broad, and wide-band visible-region-only radiometers, or radiometers having wavelength response distributions that fall into both the ultraviolet and visible regions.
Note 3—For purposes of this test method, narrow-band radiometers are those with Δλ ≤ 20 nm, broad-band radiometers are those with 20 nm ≤Δλ ≤ 70 nm, and wide-band radiometers are those with Δλ ≥ 70 nm.
Note 4—For purposes of this test method, the ultraviolet region is defined as the region from 285 to 400-nm wavelength, and the visible region is defined as the region from 400 to 750-nm wavelength. The ultraviolet region is further defined as being either UV-A with radiation of wavelengths from 315 to 400 nm, or UV-B with radiation from 285 to 315-nm wavelength.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This test method has been harmonized with, and is technically equivalent to, ISO 9059.  
1.2 Two types of calibrations are covered by this test method. One is the calibration of a secondary reference pyrheliometer using an absolute cavity pyrheliometer as the primary standard pyrheliometer, and the other is the transfer of calibration from a secondary reference to one or more field pyrheliometers. This test method proscribes the calibration procedures and the calibration hierarchy, or traceability, for transfer of the calibrations.  Note 1-It is not uncommon, and is indeed desirable, for both the reference and field pyrheliometers to be of the same manufacturer and model designation.
1.3 This test method is relevant primarily for the calibration of reference pyrheliometers with field angles of 5 to 6°, using as the primary reference instrument a self-calibrating absolute cavity pyrheliometer having field angles of about 5°. Pyrheliometers with field angles greater than 6.5° shall not be designated as reference pyrheliometers.  
1.4 When this test method is used to transfer calibration to field pyrheliometers having field angles both less than 5° or greater than 6.5°, it will be necessary to employ the procedure defined by Angstrom and Rodhe.  
1.5 This test method requires that the spectral response of the absolute cavity chosen as the primary standard pyrheliometer be nonselective over the range from 0.3 to 10-[mu]m wavelength. Both reference and field pyrheliometers covered by this test method shall be nonselective over a range from 0.3 to 4-[mu]m wavelength.  
1.6 The primary and secondary reference pyrheliometers shall not be field instruments and their exposure to sunlight shall be limited to calibration or intercomparisons. These reference instruments shall be stored in an isolated cabinet or room equipped with standard laboratory temperature and humidity control.  Note 2-At a laboratory where calibrations are performed regularly, it is advisable to maintain a group of two or three secondary reference pyrheliometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference pyrheliometer.
1.7 This test method is applicable to calibration procedures using natural sunshine only.

SCOPE
1.1 This test method covers the calibration of ultraviolet light-measuring radiometers possessing either narrow- or broad-band spectral response distributions using either a scanning or a linear-diode-array spectroradiometer as the primary reference instrument. For transfer of calibration from radiometers calibrated by this test method to other instruments, Test Method E824 should be used.  Note 1-Special precautions must be taken when a diode-array spectroradiometer is employed in the calibration of filter radiometers having spectral response distributions below 320-nm wavelength. Such precautions are described in detail in subsequent sections of this test method.
1.2 This test method is limited to calibrations of radiometers against light sources that the radiometers will be used to measure during field use.  Note 2-For example, an ultraviolet radiometer calibrated against natural sunlight cannot be employed to measure the total ultraviolet irradiance of a fluorescent ultraviolet lamp.
1.3 Calibrations performed using this test method may be against natural sunlight, Xenon-arc burners, metal halide burners, tungsten and tungsten-halogen lamps, fluorescent lamps, etc.  
1.4 Radiometers that may be calibrated by this test method include narrow-, broad-, and wide-band ultraviolet radiometers, and narrow-, broad, and wide-band visible-region-only radiometers, or radiometers having wavelength response distributions that fall into both the ultraviolet and visible regions.  Note 3-For purposes of this test method, narrow-band radiometers are those with [delta][lambda] [∧lt;=] 20 nm, broad-band radiometers are those with 20 nm [∧lt;=] [delta][lambda] [∧lt;=] 70 nm, and wide-band radiometers are those with [delta][lambda] [>=] 70 nm. Note 4-For purposes of this test method, the ultraviolet region is defined as the region from 285 to 400-nm wavelength, and the visible region is defined as the region from 400 to 750-nm wavelength. The ultraviolet region is further defined as being either UV-A with radiation of wavelengths from 315 to 400 nm, or UV-B with radiation from 285 to 315-nm wavelength.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 The method described in this standard applies to the transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels. This standard has been harmonized with ISO 9847.
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.
1.3 The calibration covered by this test method employs the use of natural sunshine as the source.
1.4 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at essentially the same tilt from horizontal as the tilt employed in the transfer of calibration.
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.
Note 1—At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Method E 913 and Test Method E 941), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 The method described in this standard applies to the transfer of calibration from reference to field radiometers to be used for measuring and monitoring outdoor radiant exposure levels. This standard has been harmonized with ISO 9847.
1.2 This test method is applicable to field radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2[pi] Steradian), field angles.
1.3 The calibration covered by this test method employs the use of natural sunshine as the source.
1.4 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth). The essential requirement is that the reference radiometer shall have been calibrated at essentially the same tilt from horizontal as the tilt employed in the transfer of calibration.
1.5 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.  Note 1-At a laboratory where calibrations are performed regularly it is advisable to maintain a group of two or three reference radiometers that are included in every calibration. These serve as controls to detect any instability or irregularity in the standard reference instrument.
1.6 Reference standard instruments shall be stored in a manner as to not degrade their calibration.
1.7 The method of calibration specified for total solar pyranometers shall be traceable to the World Radiometric Reference (WRR) through the calibration methods of the reference standard instruments (Method E913 and Test Method E941), and the method of calibration specified for narrow- and broad-band ultraviolet radiometers shall be traceable to the National Institute of Standards and Technology (NIST), or other internationally recognized national standards laboratories.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 These tables define an air mass 1.5 solar spectral irradiance distribution for use in all solar applications where a standard terrestrial spectral irradiance is required for that part of solar irradiance, diffuse, and direct, that is incident on a sun-facing, 37°-tilted surface. A similar standard for direct normal irradiance is given in Standard E891.  
1.2 These tables are modeled data that were generated using a zero air mass solar spectrum based on the revised extraterrestrial spectrum of Neckel and Labs (1), the BRITE (3, 4) Monte Carlo radiative transfer code, and the 1962 U.S. Standard Atmosphere (5) with a rural aerosol (6, 7, 8). Further details are presented in Appendix X1.  
1.3 The air mass zero (AM0) spectrum that was used to generate the terrestrial spectrum was provided by C. Frohlich and C. Wehrli (1) and is a revised and extended Neckel and Labs (2) spectrum. Neckel and Labs revised their spectrum by employing newer limb-darkening data to convert from radiance to irradiance, as reported by Frohlich (9), citing the study by Hardrop (10). Comparisons by Frohlich with calibrated sunphotometer data from Mauna Loa, Hawaii, indicate that this new extraterrestrial spectrum is the best currently available.  
1.4 The development of the terrestrial solar spectrum data is based on work reported by Bird, Hulstrom, and Lewis (11). In computing the terrestrial values using the BRITE Monte Carlo radiation transfer code, the authors cited took the iterations to 2.4500 [mu]m only. We have extended the spectrum to 4.045 [mu]m using sixteen [lambda]i values from the original Standard E892-82. Irradiance values in Standard E892-82 were computed from the extraterrestrial spectrum represented by Standard E490. The additional data points were added to account for the solar irradiance in this region that account for approximately 1.5% of the total irradiance between 0.305 and 4.045 [mu]m. The errors propagated by doing so are insignificant.  
1.5 An air mass of 1.5, a turbidity of 0.27, and a tilt of 37° were chosen for this standard because they are representative of average conditions in the 48 contiguous states of the United States.