Colorimeters and Shade Detectors

In biological alternative energy processes, in the measurement of color, and in solar energy processes, the measurement and location of shaded areas can 

Post-Oil Energy Technology After the Age of Fossil Fuels 

Color measurements use the part of the electromagnetic spectrum that is sensed by the human eye and brain. This region is approximately 400-700 nm. The colors of the rainbow are associated with specific wavelengths of visible light, as listed in Table 3.14. If colored filters such as RGB (red, green, and blue) are used, the device is called a colorimeter. If a grating or prism is used, the device is called a spectrophotometer. 

In spectrophotometric analyzers, interference filters are selected for desired wavelengths, as determined from the spectral relationship curves. Photodetectors are least sensitive in the blue end of the spectrum. This can be dealt with by using prefilters or narrow spectral ranges, which are calibrated for more sensitivity. Improvements in spectrophotometers include a flashed xenon light source with dual-beam measurement. Dual-beam machines measure the spectrum of both the light source and the reflected light for each measurement. 

Recent advances in fiber optics have allowed the light source and the photosensitive device to be remotely located from the actual sensor windows. Various cells can be installed in flow lines measuring from 0.5 to 6 in. in diameter, or in situ probes can be used. 

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