Editing Pyranometer (section)

== Explanation ==
[[File:Solar Spectrum and Spectral-Response.png|454x454px|right|Spectrum and spectral response]]
The solar radiation [[spectrum]] that reaches Earth's surface extends its wavelength approximately from 300&nbsp;nm to 2800&nbsp;nm.
Depending on the type of pyranometer used, irradiance measurements with different degrees of spectral sensitivity will be obtained.

To make a measurement of [[irradiance]], it is required by definition that the response to "beam" radiation varies with the [[cosine]] of the angle of incidence. This ensures a full response when the solar radiation hits the sensor perpendicularly (normal to the surface, sun at zenith, 0° angle of incidence), zero response when the sun is at the horizon (90° angle of incidence, 90° zenith angle), and 0.5 at a 60° angle of incidence. It follows that a pyranometer should have a so-called "directional response" or "cosine response" that is as close as possible to the ideal cosine characteristic.