| Dissolved Oxygen is the molecule of oxygen dissolved in water or other solutions.The measurement of dissolved oxygen concentration in water is very important for water environment monitoring,aquaculture,industrial production and scientific experiments.After studying and investigating the principle of dissolved oxygen measurement and the current research status of dissolved oxygen sensors both here and abroad,this paper designs a dissolved oxygen sensing system based on fluorescence quenching,which can maintain high-speed response and high-precision online monitoring.The specifics as follow:Firstly,the principle,advantages and disadvantages of the current main methods for detecting dissolved oxygen are compared and analyzed,and the principle of the dissolved oxygen sensor based on the fluorescence quenching method,the preparation method of the core components and the application advantages are mainly introduced.Through a large amount of literature,we understand the mechanism of fluorescence generation and quenching,then analyze the principle of Stern-Volmer equation demodulating dissolved oxygen concentration information,and study the fluorescence intensity detection method and fluorescence lifetime detection method.Then the preparation method of the dissolved oxygen sensor film was studied.By comparing the fluorescence spectra and stability of different materials,the ruthenium Ru(dpp)3CL2 was finally selected as the sensitive material,cellulose acetate(CA)as the sensor film matrix,and acetone as a solvent.During the preparation process,the ratio of sensitive material,substrate and solvent is changed,and the film forming effect and sensing performance under different ratios are compared to find the best ratio of film.Finally,a dissolved oxygen sensing system was designed and built,including the design of the sensor voltage regulator circuit,the composition of the sensor light source LED module and the sensor detection module.A filter is added to the fluorescence receiving part to reduce the influence of the light source and space light on the fluorescence,the photodiode is used to detect the fluorescence intensity,and the collimator lens is used to couple the collected fluorescence into the multi-mode optical fiber and perform the optical fiber spectrometer.Spectral analysis.Use the RS485 serial port to issue and return instructions to the dissolved oxygen sensor,and design the computer-side java program to collect and save the light intensity data of the port.After builting the whole system,we have tested and analyzed the system.Use the mature dissolved oxygen sensor on the market for auxiliary calibration,and design a variety of comparative verification experiments to test the repeatability,stability and corresponding time of the dissolved oxygen sensor system.Through optimized design,the detection sensitivity of the dissolved oxygen sensor system is improved.The sensitivity,stability and repeatability of the experimental results show that the system has achieved the expected design effect of the sensor. |
PDF Full Text Request