Radiometer
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A '''radiometer''' is a device used to measure the [[radiometry|radiant flux]] or power in [[electromagnetic radiation]]. Although the term is perhaps most generally applied to a device which measures [[infrared radiation]], it can also be applied to detectors operating any wavelength in the [[electromagnetic spectrum]]; a spectrum-measuring radiometer is also called a '''spectroradiometer'''.
Whenever describing a radiometer, the most important characteristics are:
* spectral range (what wavelengths)
* spectral sensitivity (what sensitivity versus wavelength)
* field of view (180 degrees or limited to a certain narrow field)
* directional response (typically cosine response or uni-directional response)
Radiometers can use all kinds of detectors; some are " thermal" that is absorbing energy and converting that to a signal, some sense photons ([[photodiode]]) having a constant response per quantum (light particle).
In a common application, the radiation detector within a radiometer is a [[bolometer]] which absorbs the radiation falling on it and, as a result, rises in temperature. This rise can then be measured by a thermometer of some type. This temperature rise can be related to the power in the incident radiation.
An early detector of infrared and visible radiation (light) was the [[Crookes radiometer]]. A more sensitive device, employing a different principle, is the [[Nichols radiometer]].
A [[Microwave radiometer]] operates in the [[Microwave]] region of the electromagnetic spectrum.
The term '''radiometer''' is occasionally used as shorthand for a [[Crookes_radiometer|Crookes radiometer]], a device in which a rotor with dark and light vanes in a partial vacuum spins when exposed to light.
==See also==
* [[Pyranometer]] (instrument)
* [[Photometry (optics)]] Main article - explains technical terms and units
{{physics-stub}}
[[Category:Electromagnetic radiation meters]]
[[Category:Radiometry]]
==External links==
*[http://www.radiometernewspin.com/ Use of Radiometer as an Alternative Energy Source]
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