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Fluorescence detection system developed sampled integrator

Author: ChenFang
Tutor: LiuGuangDa
School: Jilin University
Course: Measuring Technology and Instruments
Keywords: Sampling integrator Fluorescence Weak signal PMT Fixed-point formula
CLC: TH744.1
Type: Master's thesis
Year: 2007
Downloads: 323
Quote: 2
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Abstract


Fluorescence analysis in food hygiene , biology, life sciences and other fields has wide application , by fluorescence quantitative analysis , can provide excitation spectra , fluorescence spectra, fluorescence intensity , and other important parameters. However , given the existence of matter itself or the fluorescence generated by the excitation , generally have low fluorescence or fluorescence intensity of the fluorescence lifetime is short, and the efficiency is not high defects, so the development of the fluorescence detection system , in order to effectively extract the fluorescence from the noise signal design and practical reasonably low noise, high signal to noise ratio weak fluorescence detection circuit to improve system performance has an important role . Currently popular weak signal detection methods are lock-in amplifier and sampling points, lock-in amplifier is used to detect a minor slowly varying DC signal or signals, fluorescence detection , the lock-in amplifier is powerless, because the fluorescence signal was drowned in the noise of the pulse signal , rising and falling pulse waveform contains a wealth of high harmonics . If the lock-in amplifier , the output stage of the low-pass filter will filter out the high frequency components , resulting in distortion of the waveform . For this type of signal detection , the use of sampling integral method is a good choice . In view of this topic a lot of relevant literature , based on the proposed sample fluorescence detection system integrator development program. This topic uses a fixed sampling points detection technology, for a fixed periodic signal phase point , every one cycle of the sampling point , and the average cumulative time , be able to get an accurate amplitude information of the point , largely unaffected by noise affected. By a photomultiplier tube (PMT) for the fluorescence signal through low-noise pre- amplifier circuit and sent to the sampling integration process and to take appropriate measures after filtering fluorescence interference signal into a digital signal , and outputs into the microcontroller display . In the actual test , not only for sampling integrator input and output characteristics were tested also applied to fluorescence detection system to detect objects as aflatoxin , the whole system performance test , and the results proved that the fluorescence spectral detection system feasibility sampled integrator .

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CLC: > Industrial Technology > Machinery and Instrument Industry > Instruments, meters > Optical instruments > Physical optical instruments > Spectrometers
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