ASTM E824 - 26

1.1 This test method covers the transfer of calibration from reference to field pyranometer to be used for measuring and monitoring solar radiation. This standard is applicable to spectrally flat A, B, and C categories as defined in ISO 9060, as well as to silicon photodiode pyranometers. With respect to the overall procedure and the handling of data, this standard has been harmonized with relevant sections of ISO 9847.

1.2 This test method is applicable to radiometers regardless of the radiation receptor employed, but is limited to radiometers having approximately 180° (2π Steradian), field angles.

1.3 This method is applicable to radiometers with narrow-band spectral response functions, such as filter radiometers for measuring ultraviolet radiation, such as UV-A radiation (315 nm to 400 nm), UV-B radiation (280 nm to 315 nm), and total UV radiation (280 nm to 385 nm, or 400 nm), as well as photosynthetically active radiation (PAR, 400 nm to 700 nm) and photopic radiation (290 nm to 850 nm).

1.4 For filtered radiometers, the methods require the reference and field radiometers to be of the same type, meaning with the same or very similar passband characteristics and spectral response functions (for example, UV-A region, total solar radiation, PAR spectral region, etc.).

1.5 For filtered radiometers, the methods address transfer of calibration from reference narrow-band radiometers to field narrow band radiometers based on two approaches.

1.6 The spectral response function of the reference and field radiometers are known and available as digital/digitized or tabulated data.

1.7 The wavelength limits of the spectral response functions are known, but the spectral response functions are often not known in detail. Thus, the “cut-on” and “cut-off” wavelengths, expressed as wavelengths at which either 10 % or 50 % of the maximum spectral response function for the type of radiometer, is defined. See “passband” in Tables G177.

1.8 The calibration covered by this test method employs the use of solar radiation as the source. Calibration performed indoors using lamps as the source of irradiance is not covered in this test method.

1.9 Calibrations of field radiometers may be performed at tilt as well as horizontal (at 0° from the horizontal to the earth).

1.10 The primary reference instrument shall not be used as a field instrument and its exposure to sunlight shall be limited to calibration or intercomparisons.

1.11 Reference standard instruments shall be stored in a manner as to not degrade their calibration.

1.12 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).

1.13 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.

1.14 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.