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84 PCB007 MAGAZINE I APRIL 2018 IR and UV-Vis spectrophotometers were all de- signed with a white tungsten light, a fine-ruled grating and a single photo-detector. In 1980, Hewlett-Packard developed a totally new IR-UV- VIS spectrophotometer with no moving parts. They used a fixed holographic grating and fine 2000-pixel diode array detector (DAS). This al - lowed a spectral scan in less than one millisec- ond. This fast scan allowed programmable wave- length concentration calculations, baseline sup- pression on reaction-kinetics to be performed. The diagr am of the DAS is shown in Figure 9. Figure 8: DIY spectrophotometers are very common now on the Internet and are being built by middle and high school students. The simple colorimeters can be built using specific wavelength LEDs or a grating made from any CD. The de- tector can be a common cellphone camera or specific cameras purchased for the Raspberry PI or Arduino. Illustrated is the popular LEGO spectrophotometer kit. Figure 9: Schematic of how the new technology of a diode-array spectrophotometer works. (Source: HP brochure)