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NOVEMBER 2020 I PCB007 MAGAZINE 71 parts are available online [3] . Surely, if high- school students can build and use these spec- trophotometers, a PWB facility can. IR and UV/VIS spectrophotometers were all designed with a white tungsten light, a fine- ruled grating, and a single photodetector. In 1980, Hewlett-Packard (HP) developed a total- ly new IR/UV/VIS spectrophotometer with no moving parts. They used a fixed holographic grating and fine 2000-pixel diode array detec- tor (DAS). This allowed a spectral scan in less than one millisecond. This fast scan allowed programmable wavelength concentration cal- culations, baseline suppression on reaction-ki- netics to be performed. The first-generation DAS, HP 8450A, had five sample cells, a beam director, and software to automate data collection and analysis. The second generation, 8452A, was 38% less ex- pensive and used color displays. The third gen- eration, Agilent 8453E, is only 68% the cost of the original DAS but 25% larger wavelength sensitivity (Figure 7). The Agilent DAS is an ideal piece of instrumentation to have in your PCB chemical laboratory. It allows easy exper- imentation of wavelengths, concentration cali- bration, and automation of chemical analysis. Some of the automatic analyses performed at the HP Sunnyvale PCB shop were: • Saccharin additives • Ni component 67 additive • Nickel concentration • Impurities • Boric acid • Chloride One Agilent DAS allowed the replacement of manual titrations and an expensive atomic ab- sorption spectrophotometer (AA) for analysis of tin, nickel, gold, copper, palladium, micro- Figure 8: DIY spectrophotometers are quite common now on the internet and are being built by middle school and high school students. The simple colorimeters can be built using specific wavelength LEDs or a grating made from any CD. The detector can be a common cellphone camera or specific cameras purchased for the Raspberry Pi or Arduino. Illustrated here is the popular Lego spectrophotometer.