1 This International Standard specifies two pre-ferred methods for the calibration of field pyrano-meters using reference pyranometers.
2 One method, the outdoor calibration or type Ⅰ, employs solar radiation as the source, while the other method, the indoor calibration or type Ⅱ, em-ploys an artificial radiation source.
2.1 The outdoor calibration of field pyranometers may be performed with the pyranometer in a hori-zontal position (i.e. zero tilt) (type Ⅰa), in a tilted position (type Ⅰb), or at normal incidence (type Ⅰc) maintaining the receiver surface perpendicular to the sun's beam component.
2.2 The indoor calibration of field pyranometers may be performed using an integrating sphere with shaded (type Ⅱa) or unshaded (type Ⅱb) lamp(s), or at normal incidence (type Ⅱc) frequently using an optical bench to present the receiver surface per-pendicular to the beam of the lamp.
Types Ⅱa and Ⅱb correspond to an outdoor cali-bration under conditions of overcast and sunny sky with large light cloud fields, respectively. Type Ⅱc is comparable with the normal incidence calibration of type Ⅰc.
3 The methods of calibration specified are traceable to the world radiometric reference (WRR); traceability to the International Pyrheliometric Scale of 1956 is not permitted.
4 This International Standard is applicable to most types of field pyranometers regardless of the type of radiation receptor employed. In general, all pyranometers used for long-term monitoring of inci-dent solar irradiance may be calibrated by using the described methods, provided that the reference pyranometer has been calibrated at essentially the same tilt from horizontal as the tilt employed in the calibration.
NOTE 1 Pyranometers used for collector tests should be calibrated using a reference pyrheliometer (see
ISO 9846).