16-02-2019, 22:12
Might be of interest re using a lux meter to measure solar irradiance.
Measuring solar energy is complicated stuff. A lux meter measures the spectrum visible to the human eye and is biased to the green spectrum, PAR meters bias to the red and blue spectrum(400-700nm) with a built in reduction in response to the green spectrum as plants use blue and red: pyranometers, try to get a fairly flat response between 300 and 2800nm, nett radiometers can be thermopiles measuring low frequency energy reflected back from the earths surface etc.
The lux is one lumen per square metre (lm/m2), and the corresponding radiometric unit, which measures irradiance, is the watt per square metre (W/m2). There is no single conversion factor between lx and W/m2; there is a different conversion factor for every wavelength, and it is not possible to make a conversion unless one knows the spectral composition of the light. ( https://en.m.wikipedia.org/wiki/Lux )
Good book on this is Alex Ryer, Light Management Handbook.
http://www.google.co.uk/url?sa=t&source=...pOwhkP99cV
Measuring solar energy is complicated stuff. A lux meter measures the spectrum visible to the human eye and is biased to the green spectrum, PAR meters bias to the red and blue spectrum(400-700nm) with a built in reduction in response to the green spectrum as plants use blue and red: pyranometers, try to get a fairly flat response between 300 and 2800nm, nett radiometers can be thermopiles measuring low frequency energy reflected back from the earths surface etc.
The lux is one lumen per square metre (lm/m2), and the corresponding radiometric unit, which measures irradiance, is the watt per square metre (W/m2). There is no single conversion factor between lx and W/m2; there is a different conversion factor for every wavelength, and it is not possible to make a conversion unless one knows the spectral composition of the light. ( https://en.m.wikipedia.org/wiki/Lux )
Good book on this is Alex Ryer, Light Management Handbook.
http://www.google.co.uk/url?sa=t&source=...pOwhkP99cV