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ASTM G167-05

(Test Method)

Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer

Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer

SCOPE
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.

General Information

Status
Historical
Publication Date
30-Sep-2005
ICS
07.060 - Geology. Meteorology. Hydrology
Technical Committee
G03 - Weathering and Durability
Drafting Committee
G03.09 - Radiometry
Current Stage
Ref Project

Relations

Replaces
ASTM G167-00 - Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer
Effective Date
01-Oct-2005
Replaced By
ASTM G167-05(2010) - Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer
Effective Date
01-Dec-2010
Referred By
ASTM E772-15(2021) - Standard Terminology of Solar Energy Conversion
Effective Date
01-Oct-2005
Referred By
ASTM E2848-13(2023) - Standard Test Method for Reporting Photovoltaic Non-Concentrator System Performance
Effective Date
01-Oct-2005
Referred By
ASTM G7/G7M-21 - Standard Practice for Natural Weathering of Materials
Effective Date
01-Oct-2005
Referred By
ASTM G207-11(2019)e1 - Standard Test Method for Indoor Transfer of Calibration from Reference to Field Pyranometers
Effective Date
01-Oct-2005
Referred By
ASTM E816-15(2023) - Standard Test Method for Calibration of Pyrheliometers by Comparison to Reference Pyrheliometers
Effective Date
01-Oct-2005
Referred By
ASTM G213-17(2023) - Standard Guide for Evaluating Uncertainty in Calibration and Field Measurements of Broadband Irradiance with Pyranometers and Pyrheliometers
Effective Date
01-Oct-2005
Referred By
ASTM G90-23 - Standard Practice for Performing Accelerated Outdoor Weathering of Materials Using Concentrated Natural Sunlight
Effective Date
01-Oct-2005
Referred By
ASTM E824-10(2018)e1 - Standard Test Method for Transfer of Calibration From Reference to Field Radiometers
Effective Date
01-Oct-2005

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ASTM G167-05 - Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:G167–05
Standard Test Method for
1
Calibration of a Pyranometer Using a Pyrheliometer
This standard is issued under the fixed designation G167; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Accurate and precise measurements of total global (hemispherical) solar irradiance are required in
the assessment of irradiance and radiant exposure in the testing of exposed materials, determination
of the energy available to solar collection devices, and assessment of global and hemispherical solar
radiation for meteorological purposes.
This test method requires calibrations traceable to the World Radiometric Reference (WRR), which
represents the SI units of irradiance. The WRR is determined by a group of selected absolute
pyrheliometers maintained by theWorld Meteorological Organization (WMO) in Davos, Switzerland.
Realization of the WRR in the United States, and other countries, is accomplished by the
intercomparison of absolute pyrheliometers with the World Radiometric Group (WRG) through a
series of intercomparisons that include the International Pyrheliometric Conferences held every five
years in Davos. The intercomparison of absolute pyrheliometers is covered by procedures adopted by
WMO and is not covered by this test method.
It should be emphasized that “calibration of a pyranometer” essentially means the transfer of the
WRR scale from a pyrheliometer to a pyranometer under specific experimental procedures.
1. Scope 1.5 Calibrations of reference pyranometers may be per-
formed by a method that makes use of either an altazimuth or
1.1 This test method covers an integration of previous Test
equatorial tracking mount in which the axis of the radiometer’s
Method E913 dealing with the calibration of pyranometers
radiation receptor is aligned with the sun during the shading
with axis vertical and previous Test Method E941 on calibra-
disk test.
tion of pyranometers with axis tilted.This amalgamation of the
1.6 The determination of the dependence of the calibration
twomethodsessentiallyharmonizesthemethodologywithISO
factor (calibration function) on variable parameters is called
9846.
characterization. The characterization of pyranometers is not
1.2 This test method is applicable to all pyranometers
specifically covered by this method.
regardlessoftheradiationreceptoremployed,andisapplicable
1.7 This test method is applicable only to calibration pro-
to pyranometers in horizontal as well as tilted positions.
cedures using the sun as the light source.
1.3 This test method is mandatory for the calibration of all
1.8 This standard does not purport to address all of the
secondary standard pyranometers as defined by the World
safety concerns, if any, associated with its use. It is the
Meteorological Organization (WMO) and ISO 9060, and for
responsibility of the user of this standard to establish appro-
any pyranometer used as a reference pyranometer in the
priate safety and health practices and determine the applica-
transfer of calibration using Test Method E842.
bility of regulatory limitations prior to use.
1.4 Two types of calibrations are covered: Type I calibra-
tions employ a self-calibrating, absolute pyrheliometer, and
2. Referenced Documents
Type II calibrations employ a secondary reference pyrheliom-
2
2.1 ASTM Standards:
eter as the reference standard (secondary reference pyrheliom-
E772 Terminology Relating to Solar Energy Conversion
eters are defined by WMO and ISO 9060).
E824 Test Method for Transfer of Calibration From Refer-
ence to Field Radiometers
1
This test method is under the jurisdiction of ASTM Committee G03 on
Weathering and Durability and is the direct responsibility of Subcommittee G03.09
2
on Radiometry. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2005. Published November 2005. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2000. Last previous edition approved in 2000 as G167 – 00. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0167-05. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
G167–05
2.2 WMO Document: 3.2.12 pyrheliometer, n—see Terminology E772 and ISO
World Meteorological Organization (WMO), “Measure- 9060.
ment of Radiation” Guide to Meteorological Instruments
3.2.13 pyrheliometer, absolute (self-calibrating), n—a solar
and Methods of Observation, fifth e
...

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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).  
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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.  
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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.  
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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.  
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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.  
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Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer

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).  
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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.  
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SIGNIFICANCE AND USE
5.1 The object of this test method is to provide guidelines for the construction of a psychrometer and the techniques required for accurately measuring the humidity in the atmosphere. Only the essential features of the psychrometer are specified.
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1.1 General:  
1.1.1 This test method covers the determination of the humidity of atmospheric air by means of wet- and dry-bulb temperature readings.  
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1.1.4 Relative humidity (RH) does not denote a unit. Uncertainties in the relative humidity are expressed in the form RH ± rh %, which means that the relative humidity is expected to lie in the range (RH − rh) % to (RH  + rh) %, where RH is the observed relative humidity. All uncertainties are at the 95 % confidence level.  
1.2 Method A—Psychrometer Ventilated by Aspiration:  
1.2.1 This method incorporates the psychrometer ventilated by aspiration. The aspirated psychrometer is more accurate than the sling (whirling) psychrometer (see Method B), and it offers advantages in regard to the space which it requires, the possibility of using alternative types of thermometers (for example, electrical), easier shielding of thermometer bulbs from extraneous radiation, accidental breakage, and convenience.  
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1.3 Method B—Psychrometer Ventilated by Whirling (Sling Psychrometer):  
1.3.1 This method incorporates the psychrometer ventilated by whirling (sling psychrometer).  
1.3.2 This method is applicable within the ambient temperature range 5 °C to 50 °C, wet-bulb temperatures not lower than 1 °C and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 Warning—Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be prohibited by law.  
1.6 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. (For more specific safety precautionary statements, see 8.1 and 15.1.)  
1.7 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.

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ASTM
ASTM G213-17(2023)(Guide)
Standard Guide for Evaluating Uncertainty in Calibration and Field Measurements of Broadband Irradiance with Pyranometers and Pyrheliometers

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.

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ASTM
ASTM D4430-00(2023)(Practice)
Standard Practice for Determining the Operational Comparability of Meteorological Measurements

SIGNIFICANCE AND USE
5.1 This practice provides data needed for selection of instrument systems to measure meteorological quantities and to provide an estimate of the precision of measurements made by such systems.  
5.2 This practice is based on the assumption that the repeated measurement of a meteorological quantity by a sensor system will vary randomly about the true value plus an unknowable systematic difference. Given infinite resolution, these measurements will have a Gaussian distribution about the systematic difference as defined by the Central Limit Theorem. If it is known or demonstrated that this assumption is invalid for a particular quantity, conclusions based on the characteristics of a normal distribution must be avoided.
SCOPE
1.1 Sensor systems used for making meteorological measurements may be tested for laboratory accuracy in environmental chambers or wind tunnels, but natural exposure cannot be fully simulated. Atmospheric quantities are continuously variable in time and space; therefore, repeated measurements of the same quantities as required by Practice E177 to determine precision are not possible. This practice provides standard procedures for exposure, data sampling, and processing to be used with two measuring systems in determining their operational comparability (1,2).2  
1.2 The procedures provided produce measurement samples that can be used for statistical analysis. Comparability is defined in terms of specified statistical parameters. Other statistical parameters may be computed by methods described in other ASTM standards or statistics handbooks (3).  
1.3 Where the two measuring systems are identical, that is, same make, model, and manufacturer, the operational comparability is called functional precision.  
1.4 Meteorological determinations frequently require simultaneous measurements to establish the spatial distribution of atmospheric quantities or periodically repeated measurement to determine the time distribution, or both. In some cases, a number of identical systems may be used, but in others a mixture of instrument systems may be employed. The procedures described herein are used to determine the variability of like or unlike systems for making the same measurement.  
1.5 This standard does not purport to address 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. (See 8.1 for more specific safety precautionary information.)  
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.

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