Research And Realization Of Key Technology Of Measuring System Of Living Cell Concentration And Conductivity

The concentration of living cells is an important physiological parameter related to the growth,metabolism and productivity of living cells.If you want to observe and record the growth process of living organisms,you must have a more in-depth understanding of the changes in parameters of living cells during the growth cycle,such as number and volume,concentration,conductivity,etc.The measurement system of living cell concentration and conductivity can help researchers measure the conductivity of living cell solutions,estimate the concentration of living cells in the solution,observe and record the reproduction process of living cells,which plays an important role in researching applications in the fields of food,medicine,microbes,fermentation engineering,etc.This dissertation first introduces the research background of the subject,outlines the research significance of the subject,and introduces the development history of measuring the concentration and conductivity of living cells at home and abroad.On this basis,physical and mathematical model of the polarization of living cells are established.By analyzing the advantages and disadvantages of the existing measurement methods,the measurement structure adopted by the system is determined.The overall system measurement plan mainly includes system hardware design,control logic design and host computer software design.The hardware design part mainly includes the hardware composition of the excitation signal source,the signal conditioning circuit design and the acquisition and transmission circuit design.The control logic design part mainly includes the excitation signal source working mode configuration,acquisition and transmission logic design,focusing on the following three key technologies,namely the variable voltage design and resistance division method in the excitation signal source,the implementation method of the excitation signal source frequency sweeping and fixed frequency working mode,conditioning the realization method of the four-level conditioning circuit in the circuit is differential receiving,synchronous demodulation,low-pass filtering,low-frequency gain adjustable amplification and so on.On this basis,by building a system test environment to verify whether the three key technologies in the measurement program and the overall system function can be achieved.Tests show that the two signal output modes of single constant frequency mode and sweep mode of the excitation signal source can output stably in the frequency range of 100 kHz ~ 20MHz;Multisim simulation and actual measurement results show that the four-level conditioning circuit can achieve corresponding functions.Through the analysis of the relationship between the measured value and the dielectric constant,the concentration of living cells,and the electrical conductivity,the measurement range of the system’s dielectric constant can reach 400 pF / cm,and the conductivity measurement range can reach 40 mS / cm.The test results show that each module of the measurement system can run stably and meet the design requirements.