ASTM G183-15(2023)

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.
Designation: G183 − 15 (Reapproved 2023)
Standard Practice for
Field Use of Pyranometers, Pyrheliometers and UV
Radiometers
This standard is issued under the fixed designation G183; 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.
1. Scope G90 Practice for Performing Accelerated Outdoor Weather-
ing of Materials Using Concentrated Natural Sunlight
1.1 This practice describes deployment conditions, mainte-
G113 Terminology Relating to Natural and Artificial Weath-
nance requirements, verification procedures and calibration
ering Tests of Nonmetallic Materials
frequencies for use of pyranometers, pyrheliometers and UV
2.2 ISO Standards:
radiometers in outdoor testing environments. This practice also
ISO 877 Plastics—Methods of Exposure to Direct
discusses the conditions that dictate the level of accuracy
Weathering, Indirect Weathering Using Glass-Filtered
required for instruments of different types.
Daylight and Indirect Weathering by Daylight Using
1.2 While both pyranometers and UV radiometers may be
Fresnel Mirrors
employed indoors to measure light radiation sources, the
ISO 9060 Solar Energy—Specification and Classification of
measurement of ultraviolet and light radiation in accelerated
Instruments for Measuring Hemispherical Solar and Di-
weathering enclosures using manufactured light sources gen-
rect Solar Radiation
erally requires specialized radiometric instruments. Use of
ISO 9370 Plastics—Instrumental Determination of Radiant
radiometric instrumentation to measure laboratory light
Exposure in Weathering Tests—General Guidance
sources is covered in ISO 9370.
ISO TR 9901 Solar Energy—Field Pyranometers—
NOTE 1—An ASTM standard that is similar to ISO 9370 is under
Recommended Practice for Use
development and deals with the instrumental determination of irradiance
and radiant exposure in weathering tests. 2.3 WMO Reference:
World Meteorological Organization (WMO), 1983 “Mea-
1.3 The characterization of radiometers is outside the scope
surement of Radiation,” Guide to Meteorological Instru-
of the activities required of users of radiometers, as contem-
ments and Methods of Observation, seventh ed., WMO-
plated by this standard.
No. 8, Geneva
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3. Terminology
ization established in the Decision on Principles for the
3.1 Definitions—The definitions given in Terminologies
Development of International Standards, Guides and Recom-
E772 and G113 are applicable to this practice.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4. Radiometer Selection
2. Referenced Documents
4.1 Criteria for the Selection of Radiometers:
2.1 ASTM Standards: 4.1.1 There are several criteria that need to be considered
E772 Terminology of Solar Energy Conversion for selection of the radiometer that will be used:
G7 Practice for Natural Weathering of Materials 4.1.1.1 Function specific criteria, such as whether a
G24 Practice for Conducting Exposures to Daylight Filtered pyranometer, pyrheliometer or UV radiometer is required,
Through Glass 4.1.1.2 Task specific criteria, such as the accuracy require-
ments for the selected incident angle and temperature ranges,
and maximum response time,
This practice is under the jurisdiction of ASTM Committee G03 on Weathering
and Durability and is the direct responsibility of Subcommittee G03.09 on
4.1.1.3 Operational criteria, such as dimensions, weight,
Radiometry.
stability and maintenance, and
Current edition approved March 15, 2023. Published March 2023. Originally
approved in 2005. Last previous edition approved in 2015 as G183 – 15. DOI:
10.1520/G0183-15R23.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from International Organization for Standardization (ISO), 1, ch. de
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://www.iso.org.
Standards volume information, refer to the standard’s Document Summary page on Available from World Meterological Organization, 7 bis, avenue de la Paix, CP.
the ASTM website. 2300, CH-1211 Geneva 2, Switzerland, http://www.wmo.int.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G183 − 15 (2023)
4.1.1.4 Economic criteria, such as when networks have to be 4.3.2.3 Preferably, data on the technical characteristics and
equipped, or whether the instrument is being acquired for performance obtained from independent sources such as inde-
internal reference purposes, or for research purposes, etc. pendent testing laboratories, research institutes and govern-
ment laboratories.
4.2 Selection Related to Radiometer Type:
4.3.3 If the accuracy of the highest category of instrument is
4.2.1 Pyranometers, which measure global solar irradiance
insufficient for the application contemplated, the following
in the 300 nm to 2500 nm wavelength region, are required to
recommendations are given:
assess the hemispherical solar irradiance on surfaces of test
4.3.3.1 Hemispherical solar radiation may be measured by
specimens mounted on weathering test racks that are used by
the simultaneous deployment of a pyrheliometer and a con-
the outdoor weathering exposure community. Typically, pyra-
tinuously shaded secondary standard pyranometer to achieve
nometers are required to measure the exposure levels specified
accuracies that are greater than can be achieved by a secondary
in the applicable ASTM and/or ISO outdoor weathering
standard pyranometer alone,
standards such as those described in Practices G7, G24, G90,
4.3.3.2 Direct (beam) solar radiation may be measured
and ISO 877.
using an absolute cavity pyrheliometer employing electrical
4.2.2 Pyrheliometers, which measure direct (or, beam) solar
substitution of thermally absorbed radiation to achieve accu-
irradiance in the 300 nm to 2500 nm wavelength region, are
racies that are greater than can be achieved by a First-class
required to assess the solar irradiance reflected onto the target
pyrheliometer, and
board by the mirrors of Fresnel Reflecting Concentrators used
4.3.3.3 Specific ultraviolet wavelength bands may be deter-
in outdoor accelerated tests specified by ASTM and ISO
mined by integration of the selected wavelength bands using a
Standards described in Practice G90 and ISO 877.
scanning spectroradiometer possessing good slit function and
4.2.3 Ultraviolet radiometers are either broad band or nar-
narrow band pass characteristics to achieve accuracies that are
row band instruments covering defined wavelength regions of
greater than the most accurate narrow or broad band ultraviolet
the solar ultraviolet spectrum.
radiometers currently commercially available.
4.2.3.1 Broad-band UV radiometers usually are designed to
measure either UV-A, UV-B or some component of both UV-A
5. Practice for Use—General
and UV-B radiation.
5.1 Installation of Radiometers:
NOTE 2—Certain UV radiometers that are designated as total ultraviolet
5.1.1 When performing measurements in support of testing,
radiometers are advertised to measure over the total wavelength range
the test object and the field radiometer shall be equally exposed
from the so called UV cutoff at approximately 300 nm to 385 nm or 400
with respect to field of view, ground radiation and any stray
nm, but in fact measure mostly UV-A radiation by virtue of their very low
light that may be present. This means that the test surface and
responsivity to wavelengths below 315 nm.
the radiometer shall receive the same irradiance.
4.2.3.2 Narrow-band UV radiometers are essentially con-
5.1.2 When used to determine the irradiance accumulated
structed using interference filters that isolate narrow bands of
on solar concentrating devices such as the Fresnel reflecting
radiation having FWHM values of 20 nm, or less; their center
concentrators used in Practice G90, and other types of solar
wavelengths (CW) may reside anywhere in the UV spectrum
concentrators, it is essential that the collection system of the
from 280 nm to 400 nm wavelength—depending on the appli-
solar concentrators, such as the flat mirrors used in Practice
cation for which they are intended.
G90, do not receive direct irradiance that is unavailable to the
NOTE 3—While the World Meteorological Organization (WMO) and
optical system that connotes the pyrheliometer required.
the International Standards Organization (ISO) have established require-
5.1.3 The need for easy access to the radiometer for
ments for Secondary Standard and High, Good, and Moderate Quality
maintenance operations shall be considered in selecting the
pyranometers and pyrheliometers, specifications and required operational
installation site, mount, etc.
characteristics of different classes of ultraviolet radiometers have not been
addressed by either organization.
5.2 Electrical Installation:
NOTE 4—High Quality instruments are not necessary for all applica-
5.2.1 The electrical cable employed shall be secured firmly
tions.
to the mounting stand to minimize the possibility of breakage
4.3 Selection Related to Measuring Specifications:
or intermittent disconnection in severe weather.
4.3.1 As a first step, all possible ranges of measuring
5.2.2 Wherever possible, the electrical cable shall be pro-
parameters such as temperature, irradiance levels, angles of
tected and buried underground—particularly when recording
incidence, tilt angles, and station latitude, must be compiled.
devices, controllers, or converters are located at a distance. Use
4.3.2 Next, documentation must be compiled of available
of shielded cable is highly recommended. The cable, recorder
information about the technical characteristics, and the techni-
and other electronic devices, shall be connected by a very low
cal and physical specifications of the relevant radiometers
resistance conductor to a common ground.
given by:
5.2.3 Contact the manufacturer of the radiometer being
4.3.2.1 The WMO and ISO classification of pyranometers
installed to establish the maximum allowable cable length
given in the WMO Guide, and in ISO 9060 and ISO 9370
permissible for the instrument’s impedance so as to preclude
(which together define the specifications to be met by different
significant signal loss (see 5.4.5.2 for additional requirements).
categories of pyranometers and pyrheliometers),
5.2.4 When hard wiring electrical connections, all exposed
4.3.2.2 The data specification sheets obtained from the junctions shall be weatherproofed and protected from physical
manufacturer, and damage.
G183 − 15 (2023)
5.2.5 Establish and identify the polarity of all relevant noise for subsequent attention. Further, check the condition of
connections prior to connecting to the recording device, ventillation unit filters and clean or replace as necessary.
converters, or controllers. Make all connections in accordance 5.3.2.6 Perform a cursory check of the output data on at
with the manufacturer’s instructions. least a weekly basis to determine if data being recorded are
plausible in relation to the conditions being experienced.
5.3 Required Maintenance Activities:
5.3.3 Monthly Routine Inspection and Maintenance:
5.3.1 Inspection:
5.3.3.1 Examine the color-indicating desiccant for all instru-
5.3.1.1 Whenever possible, inspect radiometers employed
ments where the silica gel container is accessible. If moisture
in continuous operation at least once each day. Inspection and
is indicated, replace the desiccant.
maintenance activities of specific attributes described in the
NOTE 8—If desiccant is consumed rapidly, the cause might be a
following sections should be carried out daily, monthly and
defective seal of the instrument’s window, a defective electrical connec-
yearly as indicated.
tion into the instrument case, or a defective O-ring associated with the
desiccant chamber.
NOTE 5—It should be noted that the quality of data obtained using total
5.3.3.2 Attention should be paid to the transmission and
solar and solar ultraviolet radiometers depends strongly on the amount of
personal attention given during the observation program.
amplification of signals. Perform both visual and electrical
checks of the cable and amplifier (when used). These inspec-
5.3.2 Daily Routine Inspection and Maintenance:
tions shall also be performed when any component of a
5.3.2.1 The exterior glass domes and/or diffusers or
measuring system has been replaced, or after any anomalies
windows, shall be inspected daily and cleaned at least once
have been detected in the data.
each week or more often whenever dust or other deposits are
5.3.4 Quarterly Inspection and Maintenance:
visible. Cleaning shall occur by spraying with deionized water
5.3.4.1 In those radiometers where the desiccant is not
and wiping dry with non-abrasive and lint-free cloth or tissue.
visible, remove the desiccant cover and inspect the desiccant
It is recommended that this inspection and possible cleaning be
for dryness. If moisture is indicated, replace the desiccant. Care
performed early each day.
should be exercised to ensure that the desiccant container’s
5.3.2.2 If frozen snow, glazed frost, hoar frost or rime is
cover is closed completely (manufacturer’s instructions should
present, remove the deposit very gently, initially with the
be followed with respect to ensuring the tightness of the cover,
sparing use of a de-icing fluid or a warm lint-free cloth,
or cap).
appropriate for the type of glass dome, window, or diffuser,
5.3.4.2 Verify that the responsivities of all radiometers have
after which the glass dome, window, or diffuser shall be wiped
not changed to the extent that they are out of tolerance. This
clean and dry.
can be done by comparison to another radiometer that has the
5.3.2.3 After heavy dew, rain, sleet, snow or frost buildup,
same spectral response function or by determination that the
check to determine if condensation is present inside the dome,
ratio of, for example, UV-B to UV-A irradiance has remained
or on the receptor or diffuser surface. If condensation is
essentially the same (if both measurements are being
discovered inside the dome, on the receptor or diffuser surface
performed), or, as will usually be the case, if the ratio of total
of domed radiometers, the instrument’s manufacturer shall be
solar UV irradiance to total solar irradiance has remained
contacted to determine a course of action.
essentially the same for clear day solar noon conditions.
5.3.5 Semi-annual Inspection and Maintenance:
NOTE 6—The user may attempt to “dry out” the radiometer by elevating
5.3.5.1 Use an inclinometer to determine the inclination of
its temperature, either in natural sunlight or in the laboratory, to 50 °C. If
all radiometers mounted at tilts from the horizontal. Inspect the
the condensation is eliminated, the radiometer‘s calibration constant shall
be checked prior to being returned to service.
inclination angles of all pyranometers and UV-radiometers
including the spirit level of all horizontally mounted radiom-
5.3.2.4 When hard-to-remove deposits of air pollution or
eters.
local contamination is observed on a radiometer’s exterior
5.3.6 Yearly Inspection and Maintenance:
window, first apply deionized or distilled water on the surface.
5.3.6.1 When calibration schedules do not require annual re
If the use of a detergent solution is indicated, a prepare a 2 %
calibration, special attention should be paid to the possibility of
solution of a mild dish washing detergent and gently apply to
drift in the sensitivity (that is, the calibration factor) of the
the surface. Use a soft, lint-free muslin cloth to gently rub the
radiometer. This shall be accomplished by use of either a field
surface if required. In either case, thoroughly rinse the surface
re calibrator (in the case of certain UV-A and UV-B radiom-
with deionized or distilled water, after which it the window
eters) or a field reference radiometer maintained by the
shall be wiped clean and dry. Water spots should not be evident
testing/measuring facility for that purpose.
on the surface. However, care should be exercised to avoid
5.3.6.2 Inspect all radiometers for general deterioration of
scratching the surface.
the instrument—including domes and windows (to detect
NOTE 7—The user may use optics cleaning compressed air to blow
chips, cracks, or the development of any optical disparity), the
away all remaining water droplets from the surface after cleaning. Use
receiver coating (to detect discoloration, loss of material,
small, controlled puffs of air, being careful not to discharge any propellant
that may leave a residue on the window. Check for any streaking or lint
left by the cleaning materials and repeat if necessary.
This is most easily achieved by comparing with a UV radiometer of the same
5.3.2.5 When used, check the operational state of the
model.
ventilator or air blower at least weekly and note any unusual A protractor scale equipped with a rotatable spirit level.
G183 − 15 (2023)
simultaneously, or at a time interval much shorter than the rate of change
checking, or cracks), and seals (to detect severe discoloration,
of the irradiance and the response time of the radiometer.
cracking, degradation, etc.).
5.3.6.3 When either drift in sensitivity greater than the
5.4.2.4 The recommended method is to take readings with a
tolerance established by the testing/measuring facility, or
short-term integration, to apply a data check and then to
greater than permitted by the applicable standards or
perform data compression corresponding to a suitable interval.
specifications, or when any degradation of instrument compo-
NOTE 13—This is only possible with complex data acquisition systems.
nents is noted, the manufacturer should be contacted to
determine the advisability of either replacing the instrument or
5.4.3 Integration of Data:
returning the instrument for refurbishment.
5.4.3.1 There are two systems of data integration: (1)
Analog using an operational amplifier connected to the
NOTE 9—In the event that component degradation is observed, a field
sensitivity check should be performed prior to contacting the manufac- integrator, and (2) digital by sampling the voltage output from
turer.
the pyranometer.
5.3.6.4 When used, inspect the air channels of ventilators or 5.4.3.2 When using analog integration, check the precision
and linearity of the integration system on a monthly basis.
blowers and remove any dirt and debris that may have
collected.
5.4.3.3 When using digital sampling, check the precision of
the analog/digital converter, as well as the validity of the
5.4 Recording of Measured Data:
sampling frequency, at appropriate intervals (e.g. use Nyquist
5.4.1 Recording systems fall into three principal classes:
criterion). Follow the manufacturer’s instructions for sampling
5.4.1.1 Those providing a series of individual values,
frequency.
5.4.1.2 Continuous-line or intermittent-dot recorders pro-
5.4.4 Time Base:
viding autographic traces, and,
5.4.4.1 Time accuracy shall be linked to a recognized
NOTE 10—Potentiometric strip-chart recorders with integration and
universal time reference and should be better than 1 min., and
voltage time integrators are in wide use.
should be better than 1 s for users that are interested in
5.4.1.3 Automatic data acquisition systems which can de-
measuring solar irradiance with high accuracy by correcting for
liver either individual values or integrated totals over a
solar zenith angle dependence. It is therefore necessary to
specified period of time.
check the reference time at appropriate intervals.
NOTE 11—Microprocessor controlled data loggers using a variety of
NOTE 14—GPS or Reference to Radio Station WWVB, 60kHz, Ft.
support systems for data storage have become common.
Collins, CO, which is operated by the National Institute of Standards and
5.4.2 Sampling Rate:
Technology, is recommended. It is noted that inexpensive GPS or
5.4.2.1 When making instantaneous individual readings, quartz-crystal single-frequency radios set to this frequency are available
from various sources.
choose the length of the interval over which the series of
readings extends and the number of readings comprising the
5.4.4.2 When comparing solar and ultraviolet irradiance
measurement so as to ensure that the derived mean affords a
data between weathering sites, the data should be referenced to
representative value for the desired time interval. This applies
solar time to facilitate analysis. The equation-of-time may be
equally to a series of readings recorded by means of a fast
used to compute the solar time from local time.
response multi-channel automatic data logging system and to a
5.4.5 Impedance Considerations:
series of measurements recorded manually using a millivolt-
5.4.5.1 The input impedance of the amplifier, recorder, or
meter or potentiometer.
data logger, shall be at least 1000 times the value of the output
5.4.2.2 The frequency of the readings depends on the
impedance of the radiometer being used. If this is not the case,
application and the system characteristics as illustrated by the
corrections must be applied.
following questions:
5.4.5.2 The length of the cable and its cross-section must be
(a) What is the smallest time interval of interest?
such that the resistance of the cable will not be greater than the
(b) What are the response time and accuracy of the
output impedance of the radiometers in use. The total imped-
radiometer being used?
ance of the radiometer and cabling shall in any case be less
(c) Are the measurements to be instantaneous values ob-
than one-one-thousandths of the input impedance of the
tained from a sample-hold instrument or short time integrated
recording device employed.
values obtained with an integrator (that is, a voltage/frequency
5.4.5.3 To minimize any effects of impedance mismatch,
converter and a counter)?
position voltage/current converters as close as possible to the
(d) Does the data acquisition system compress data?
radiometer.
5.4.2.3 Depending on the answers to these questions, the
5.4.6 Accuracy of the Electronics:
sampling rate can range from one sample measurement per
minute to one sample per second, or faster. Generally, for the
5.4.6.1 Radiometer outputs are usually of the order of
calculation of average values over periods of between 0.1 h and
millivolts. Although electrical instrumentation is usually
1.0 h, 100 samples allow the average values to be estimated
shielded, the radiometer’s sensor, the body of the radiometer,
with sufficient accuracy.
and the cabling are nonetheless vulnerable to electromagnetic
noise, or interference (EMI), which can produce very-short-
NOTE 12—In solar energy applications, a pyranometer or pyrheliometer
term voltage changes. For this reason, it is preferable to
signal output is only one of several parameters being measured. Special
attention must be given to ensure that all measurements are made integrate the output signal electronically using an appropriate
G183 − 15 (2023)
voltage/frequency converter employing an integration time of type, is either provided by, or may be obtained from, the
at least 1 s for each reading. This can be programmed internally manufacturer. The characterized behavior is also sometimes
for digital recorders. available from national and international organizations who
5.4.6.2 The resolving power of the data acquisition system have been chartered to perform certain measurements as
shall be at least a factor of 100 (two orders magnitude) better independent organizations. In any case, these characterized
than that of the radiometer’s output signal (in terms of data are usually available as plots of instrument sensitivity for
...