Design Of Measurement System For Living Cell Concentration And Conductivity Based On Capacitance Method

As the basic unit of life form,observing and recording the number and morphological changes of cell growth process can enable people understand the biological growth process in more detail.The living cell concentration and conductivity measurement system based on capacitance method can detect the changes of cells in the process of growth,and is widely used in many fields,such as biopharmaceuticals,medical and health care,food fermentation and other fields.Firstly,this dissertation introduces the research background of the project,emphasizes the significance of the research,discusses the development of the measurement of living cell concentration and conductivity at home and abroad,and analyzes the advantages and disadvantages of each scheme by comparing the different measurement schemes.Combined with the existing measurement methods,an improved overall scheme is put forward,the module composition of the scheme is introduced,and the functions and relations of each part are described.Secondly,the hardware design and software design of the system are described in detail.The system includes detection module,excitation signal source module,conditioning module,acquisition and conversion module and upper computer.The hardware part describes the specific composition and functions of each module in detail,including the structure size and waterproof design of sensing module,the scheme of signal source and circuit design,differential reception,synchronous demodulation,low-pass filter,low-frequency gain circuit design of conditioning circuit,analog-to-digital conversion module,voltage conversion module and transceiver circuit design of acquisition circuit.The software part includes the selection of working mode of signal source,register configuration,register configuration of acquisition and transmission circuit,logic flow of oversampling,etc.Finally,the system test environment was built,and the software and hardware tests of the living cell concentration and conductivity measurement system were completed.Two output modes of excitation signal source,single-frequency mode and sweep mode,are tested and the output can be stable in the frequency range of 100 kHz to 20 MHz.The conditioning circuit has been debugged,and all levels of circuits can work normally.The acquisition and transmission function of the acquisition module is tested.Verify the display function of the upper computer.After analyzing the measured data,the conductivity measurement range of the system can reach 0~40mS/cm,and the dielectric constant can reach 0~400pF/cm.The test results show that each functional module of the measurement system can run stably and meet the design requirements.