The measurement of uric acid based on the optical absorption at visible light spectrum is investigated and tested. Sensing in the visible region was conducted for determination of suitable wavelength that produces high sensitivity and accuracy performance based on the Beer-Lambert law calculation. In this work, the uric acid is detected by detecting sodium urate as a product of chemical reaction between uric acid with sodium hydroxide buffer. The setup has been tested for uric acid concentration ranging from 15 mg/dL to 85 mg/dL. Three wavelengths have been analyzed which are 460 nm, 525 nm and 630 nm. Measured data at 460nm wavelength exhibits the highest sensitivity, which is 0.0012 (mg/dL)-with 86.51% accuracy. Detection of uric acid at visible light spectrum offers a low-cost sensor based on visible LEDs and photodiode is possible to be realized.
A plastic optical fiber (POF) temperature sensor with high sensitivity is experimentally demonstrated in this work. The temperature sensor is realized by a combination of macrobending and an unclad region in the fabrication of its sensor head. The POF sensor is bent into a balloon-like structure in order to introduce the effect of macrobending. For the optimization of the sensor performance, the bending radius of the balloon-like structure is varied. Experimental results suggest that the performance is optimized when the bending radius is fixed at 55 mm. With this amount of bending radius, temperature sensitivity of up to
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can be achieved in the range from 40°C to 80°C, with linearity of 0.99 and resolution of 0.45°C. This technique is found to improve the POF temperature sensitivity in comparison to previous developments.
Optimization of light source wavelength for ammonia detection in surface water is presented in this work. For the ammonia detection, the surface water sample is mixed with sodium chloride and nessler reagent, whereas the sensor head consists of unclad plastic optical fiber. The unclad region has a length of 1 cm and the cladding is removed by immersing it in acetone solution. Experimental results indicate that the output light intensity of the sensor has linear relationship with the ammonia concentration. At the wavelength of 510 nm, the output light increases linearly as the ammonia concentration varies from 0.07 mg/L to 8.97 mg/L. At the same wavelength, the proposed sensor achieves the sensitivity of 0.0139 (mg/L) -1 , accuracy of 99.59% and resolution of 0.72 µg/L. The analysis of light source wavelength reveals that a wavelength range from 450 nm to 580 nm produces the optimized performances. Within this wavelength range, the proposed sensor achieves sensitivity of higher than 0.01 (mg/L) -1 , accuracy of higher than 99% and resolution of less than 1 µg/L.
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