This document specifies two preferred methods for the calibration of pyranometers using reference pyranometers; indoor (Type A) and outdoor (Type B).
Indoor or type A calibration, is performed against a lamp source, while the outdoor method B, employs natural solar radiation as the source.
Indoor calibration is performed either at normal incidence (type A1), the receiver surface perpendicular to the beam of the lamp or under exposure to a uniform diffuse lamp source using an integrating sphere (type A2).
Outdoor calibration is performed using the sun as a source, with the pyranometer in a horizontal position (type B1), in a tilted position (type B2), or at normal incidence (type B3).
Calibrations according to the specified methods will be traceable to SI, through the world radiometric reference (WRR), provided that traceable reference instruments are used.
This document is applicable to most types of pyranometers regardless of the type technology employed. The methods have been validated for pyranometers that comply with the requirements for classes A, B and C of . In general, all pyranometers may be calibrated by using the described methods, provided that a proper uncertainty evaluation is performed.
Unlike spectrally flat pyranometers, non-spectrally flat pyranometers might have a spectral response that varies strongly with the wavelength even within the spectral range from 300 to 1 500 nm, and therefore the calibration result may possibly be valid under a more limited range of conditions.
The result of a calibration is an instrument sensitivity accompanied by an uncertainty. This document offers suggestions for uncertainty evaluation in the annexes.