PD ISO/TR 9901:2021 pdf download – Solar energy — Pyranometers — Recommended practice for use.
2 Normative references There are no normative references in this document. 3? Terms? and? definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https://www.iso.org/obp — IEC Electropedia: available at http://www.electropedia.org/ 3.1 pyranometer radiometer designed for measuring the irradiance on a plane receiver surface which results from the radiant fluxes incident from the hemisphere above within the wavelength range from approximately 0,3 µm to about 3 µm to 4 µm [SOURCE: ISO 9060:2018, 3.5, modified — Note 1 to entry was deleted.] 3.2 hemispherical radiation solar radiation received by a plane surface from a solid angle of 2π sr [SOURCE: ISO 9060:2018, 3.1, modified — Note 1 to entry was deleted.] 3.3 global horizontal irradiance GHI hemispherical radiation (3.2) received by a horizontal plane surface, also denoted as G [SOURCE: ISO 9060:2018, 3.2, modified — “GHI” was added as abbreviated term and “also denoted as G” was added at the end of the definition.]
3.11 reflected? horizontal? irradiance RHI ground-reflected irradiance incident upon a surface, oriented horizontally facing down [SOURCE: IEC 61724-1:2017] 3.12 accuracy class class of measuring instruments or measuring systems that meet stated metrological requirements that are intended to keep measurement errors or instrumental uncertainties within specified limits under specified operating conditions [SOURCE: JCGM 200:2012] 3.13 sample data acquired from a sensor or measuring device [SOURCE: IEC 61724-1:2017] 3.14 sampling interval time between samples [SOURCE: IEC 61724-1:2017] 3.15 record data recorded and stored in data log, based on acquired samples [SOURCE: IEC 61724-1:2017] 3.16 recording interval time between records [SOURCE: IEC 61724-1:2017] 3.17 clearness index k ratio of the global horizontal irradiance (3.3) to the irradiance that would be available without the earth’s atmosphere (i.e. the GHI divided by the extra-terrestrial irradiance received at the same sun incidence angle, k = G/G o ) Note 1 to entry: The extra-terrestrial irradiance at normal incidence used for calculation of the clearness index is the Solar constant (1361,1 W/m²) [ 17 ] corrected by a sinusoidal variation of amplitude 3,3 % to account for the sun-earth distance variation over the year. The clearness index may be considered as an attenuation factor of the atmosphere or the atmospheric transmittance.