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This study aimed to design a simple and low-cost visible spectrophotometer for the detection of
the absorbance of colorful metallic solutions. The designed instrument has a tungsten white light
bulb source, a light dependent resistor (LDR) as a sensor, a diffraction grating for light
dispersion, a converging lens to collimate the light, filters of different wavelengths, a digital
voltmeter, and an ammeter as a detection element. To maintain a constant light intensity, a
commonly used power supply was set at 6 V for the light source bulb. The instrument was
designed to have a simple and compact size of 55 cm × 12cm × 22 cm in length, width, and
height, respectively.
The performance of a newly designed spectrophotometer has been tested on solutions of copper
sulfate (CuSO4) and chromium chloride (CrCl3) at different filter wavelengths. The results show
a linearly dependent absorbance as a function of concentration for these four filters‘ wavelengths
(blue, red, yellow, and yellow-green). The R squared values were in the order of 97 % with an
error of 3 % and 98 % with an error of 2 %, respectively. This is consistent with the theoretical
R-squared values and the commercial UV-Vis spectrophotometer, with minor differences. The
absorbance as a function of the wavelength measuring capacity of the instrument is also tested
with copper sulfate (CuSO4), chromium chloride (CrCl2.216), and nickel chloride (NiCl2)
solutions at a constant concentration. The R2
values of these graphs were in the order of 98 %
with an error of 2 %, 97.7 % with an error of 2.3 %, and 92 % with an error of 8 %, respectively.
The shapes of the graph of absorbance as a function of wavelength for these samples have a
close similarity with the absorbance graphs of the Commercial UV-Vis spectrophotometer
(DR6000) with only small differences. It is believed that this newly designed spectrophotometer
has a low cost and can be used for the detection of colorful solution samples in low-income
countries like Ethiopia. |
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