Solar Radiation- Measurement and Data

                    Sun radiates around e+17 joules of energy per second to the earth. This can be calculated or found out using certain equipments that can measure solar energy. Some of the instruments that can measure solar energy are:
*Pyrheliometer
*Pyranometer
*Pyrgeometer
*Pyradiometer
Pyrheliometer:
                    This is an instrument used to measure the intensity of direct solar radiation at normal incidence, it can either be a primary standard instrument or a secondary instrument scaled by reference to a primary instrument. The latter have sometimes been called actinometers.
Pyranometer:
                    This is an instrument where measurement is done from the solar radiation received from the whole hemisphere. It is suitable for the measurement of the global or sky radiation usually on a horizontal surface.Sometimes the term "solarimeter" is used instead of pyranometer.If shaded from the beam radiation by a shade ring it measures diffuse radiation.
Pyrgeometer:
                    This instrument is used for the measurement of terrestrial radiation only.
Pyradiometer:
                    This is an instrument used for the measurement of both solar and terrestrial radiations i.e the net atmospheric radiation on a horizontal upward facing black surface at ambient air temperature.