FOR UNATTENDED NORMAL INCIDENCEDIRECT SOLAR RADIATION MEASUREMENT
Introduction
Solar radiation is the driving force behind biological and geophysical processes in meteorology, climate and our environment. The sun irradiates the top of the earth’s atmosphere at an average intensity of 1367 W/m². As the solar rays travel through our atmosphere they are absorbed and scattered. This results in different components of solar radiation reaching the earth’s surface. The direct component travels in a straight beam from the sun, whilst a diffuse component comes from all directions, due to the atmospheric scattering process. A pyrheliometer is an instrument designed specifically to measure the direct beam solar irradiance with a field of view limited to 5°. This is achieved by the shape of the collimation tube, with precision apertures, and the detector design. The front aperture is fitted with a quartz window to protect the instrument and to act as a
professional filter that passes solar radiation between 200 nm and 4000 nm in wavelength. CHP 1 includes a rain shield and integrated alignment aids.