Signal Processing Circuit Design and Analysis of an Optical Ozone Detector
| Autor: | Hung-Chi Lin, 林弘麒 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 The purpose of this study is to design an apparatus with an ultraviolet (UV) light beam of λ=253.7 nm and a reaction chamber for ozone and UV light, based on Beer-Lambert law. The chamber products the voltage signal of reference (VR) and the voltage signal of detection (VD) generated by photodiode sensing. The chamber uses the same light source. After the injection of ozone, because the voltage change is too small, according to Beer-Lambert law, the logarithmic process is applied to the reference signal (VR) and the detection signal (VD), and the output signal is amplified through the amplifier circuit. The noise signal is filtered by a second-order low-pass filter circuit, and the cut-off frequency of 3 Hz has the best filtering effect. The light intensity is mainly affected by high voltage ceramic capacitors and the length of the chamber. The light source intensity is found more stable when the high voltage ceramic capacitor is equal to 5 pF. The sensitivity is more excellent when the chamber length is designed as 200 mm. In conclusion, the best system sensitivity is 1.6 mV/ppb when the chamber length is 200 mm and magnified 2,000 times. In addition, the output voltage can anti-speculate ozone concentrations. The voltage obtained is approximately linear relationship with the ozone concentration. The future of the system circuit may be integrated on the chip, and toward the development of portable ozone detector. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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