EKO INSTRUMENTS CO., LTD. - Pyranometers MS-802/802F/402/402F/602 - Instruction Manual Ver.13
Table A-1. Definitions of Terms
Hemispheric Solar Irradiance
Cosine-weighted solar irradiance received over a solid angle of
2πsr on a plane surface, expressed in units of W/m
2
or kW/m
2
.
Global Solar Irradiance, Global
Horizontal Irradiance (GHI)
Hemispherical solar irradiance received on a horizontal plane
surface, expressed in units of W/m
2
or kW/m
2
.
Direct Solar Irradiance, Direct
Normal Irradiance (DNI)
Normal-incidence solar irradiance received over a small solid angle
which includes the circum solar irradiance, expressed in units of
W/m
2
or kW/m
2
.
Diffused Solar Irradiance, Diffused
Horizontal Irradiance (DHI)
Hemispherical solar irradiance without the direct solar irradiance,
i.e. indirect irradiance of the scattered solar radiation (by air
molecules, aerosol particles, clouds, etc.), expressed in units of
W/m
2
or kW/m
2
.
A radiometer designed to measure the hemispheric solar irradiance
over the wavelength range of about 300 to 3,000nm.
A radiometer which measures the direct solar irradiance over a
certain solid angle including the circumsolar irradiance.
World Radiation Reference
(WRR)
Radiometric reference instrument system which has an uncertainty
of less than +/-0.3%, expressed in SI units.
This reference is maintained by the World Meteorological
Organization (WMO), and it has been issued since January 1, 1980
An ISO norm (International Standard). The first edition was
published in 1990, then the second edition was revised in 2018.
Based on the performance of each characteristic, Pyranometer is
classified into three classes A, B, and C, and specifications of
"Spectrally flat radiometer" and "Fast response radiometer" are set
as sub-categories.
Pyrheliometer is classified into 4 classes of AA, A, B and C based
on the performance of each characteristic, and specifications of
"spectrally flat radiometer" and "Fast response radiometer" are set
as sub-categories.
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