A Design Of And Research On The Spectral Liquid Signature Analyzing System

The detection and analysis of liquid are significant in the fields such as environmental protection, medicine, food and safety inspection etc. With the improvement of living conditions, the consciousness of environmental protection is becoming stronger than ever. There are higher and higher requirements to the pollution control and quality detection of food, drink, medicine and industrial fluid. The research on practical and effective analytical methods and instruments based on advanced technology is an urgent demand. The spectral liquid signature analyzer introduces spectral analysis method into liquid analysis technology and studies the liquid sample synthetically. The physical and chemical property information of the liquid is acquired by monitoring the drop formation process under a certain measuring condition, and thus the qualitative and quantitative measurements and discrimination of liquids are realized.Through the merging of spectral analysis method and liquid analysis technology, the spectral liquid signature analyzer combines the fiber, capacitive drop analysis method with miniature spectrometer. The relationship between the sample liquid drop's profile information at different time with the electrical and optical information of the liquid drop can be gained, as well as the spectral information of the liquid sample in the set waveband of miniature spectrometer. And after data merging the three-dimensional liquid fingerprints determined by the physical, chemical and mechanical properties of the liquid sample are available. As the fiber and capacitive liquid drop analysis are not suitable for some liquids and the application range is limited, the spectral method may be utilized to gain the character information of liquid in this condition. And in the application of liquid identification, for the liquid samples that can't be distinguished with the set waveband miniature spectrometer, the discrimination function can be realized with the fingerprint data of the liquid drop. Moreover, for different liquids with similar fingerprint information, the discrimination ability can be also enhanced by spectrum information of liquids. The quantitative analysis of the specific component in liquid sample can be approached with the infrared spectrum analysis method, with the waveband of the miniature spectrometer be setted in the wavelength range in which the liquid sample has absorption phenomenon. The spectral liquid signature analysis method integrates the high speed, convenience of the spectrum analysis with the multifunction characteristics of liquid drop analysis. The application of spectral analysis makes it possible for research on the chemical composition of the liquid sample, which broadens the application fields of the liquid drop analysis technology.For the profile features of different liquid drops are different due to their physical and chemical characteristic differences, the image drop analysis method is also studied. With capacitance drop analysis method the drop volume obtained will be influced by the dielectric constant of the liquid. With the image drop analysis method this problem can be avoided, and more importantly this method can be used to analysis the liquid drop's profile feature and to study the mechanical characteristics of the liquid. The image drop analysis method can be utilized solely and the profile characteristic fingerprints of the liquid drop are obtained. Moreover, the image drop analysis method can be as replenishment to other drop analysis methods.The dissertation covers the following aspects concerning the main work and creative researches.1. The spectral analysis theory is introduced to the liquid drop analysis technology and an integrated measuring instrument is developed through the technique merging. The near infrared miniature fiber spectrometer is applied in the system to acquire the spectrum of the liquid sample. Based on the consideration of structure coupling and the development of on-line analytical instrument, the mechanical and optical structures as well as signal processing circuit of the spectral liquid signature analyzer are designed.2. A flowing cuvette is introduced to the spectrum measuring part so as to solve the problem of consistency of the measurement condition for different liquid samples. During the drop formation process, the optical path changes with the growth of the drop. If the spectrum of the liquid sample were measured directly through the growing drop, it would be difficult to assure the same optical path length for different liquid samples, which would bring difficulty to quantitative analysis of liquid. The structure of the liquid drop analysis makes it impossible to measure the absorption spectrum directly through the liquid drop. Thus a flowing cuvette is utilized in the spectrum measurement, and the spectrum measurement of different liquid samples can be carried out with the fixed optical path length under the same conditions. 3. With the spectral liquid signature analyzer, the fiber, capacitive signal and the spectrum of the liquid sample can be captured simultaneously. The three-dimensional liquid fingerprints reflecting physical, chemical and mechanical properties of liquid are obtained after data processing. The fine discrimination between different liquid samples may be done with the integrated characteristics embodied in the three-dimensional fingerprints.4. The growing process of the liquid drop is recorded by a CCD camera, and the analysis of the liquid drop images is realized. The profile characteristic parameters of the liquid drop are extracted and can be used to discriminate different liquids.5. Experiments have been conducted with the spectral liquid signature analyzer, and a liquid database is established by using the liquid property data from the experiments. Data inquiry and other management operations to the database can be done with the application program, and the qualitative discrimination of liquid is realizable with the database.6. Chemometrics is applied to preprocess the spectroscopic data and to establish the quantitative analysis model. The feasibility of this method has been proved through the modeling the multi-component liquids.