Research And Development Of Data Acquisition System For Triple Quadrupole Mass Spectrometer

In the field of analytical instruments,triple quadrupole mass spectrometer is widely used in clinical medicine,food safety and other fields due to its wide detection range and strong qualitative and quantitative ability.However,the instrument has not been commercialized in China.The function of the triple quadrupole mass spectrometer data acquisition system is to collect and analyze the ion signals to obtain the mass spectrogram,so it is the key technology of the instrument.A data acquisition system is developed for the triple quadrupole mass spectrometerIn this paper,the characteristics of the ion signal in the triple quadrupole mass spectrometer were analyzed,and the overall scheme was developed according to the signal characteristics and instrument requirements.Zynq was selected as the main control chip,the signal conditioning circuit was designed,DDR3 memory was adopted,gigabit Ethernet was selected for communication between the upper and lower computers,and two data processing algorithms were matched.At the hardware level,Zynq is a chip integrated with FPGA structure and ARM kernel,with high integration and performance.It is a new attempt to apply it in the data acquisition system of triple quadrupole mass spectrometer.The function of the signal conditioning circuit is to amplify the weak current pulse signal,convert it to IV,convert the level and so on,so as to meet the Zynq acquisition requirements.Ethernet speeds can reach 1,000 Mbps.DDR3 data rate is 1066 Mbps.At the software level,the system is divided into 8 modules by adopting the modular design method.Among them,the counter bit width is 32 bits,sampling frequency is 400 MHz,FIFO is used as internal temporary cache,and Zynq and external DDR3 data transmission function is realized by DMA technology.The program implementation and simulation test of each module are carried out respectively according to the collaborative working characteristics of Zynq internal PL and PS.At the algorithm level,cubic spline interpolation is selected for curve fitting according to the time discretization of the collected data.According to the need of precise peak search,the algorithm based on continuous wavelet transform is selected to search the peak.MATLAB platform is used to realize the application of these two algorithms in data processing.Finally,the system is tested and verified.Simulation experiment was carried out in the test experiment.The test signal was 1k Hz～70MHz pulse signal,and the error between the experimental result and the theoretical value was less than 0.035‰.In the verification experiment,the standard tuning liquid of polypropylene glycol was injected into the sample,and the parameters(peak value and half peak width)of the mass spectrogram were all consistent with the tuning standard of the instrument.The data acquisition system designed in this paper is fast and highly integrated,which solves the difficulties in the research and development of the data acquisition system of the triple quadrupole mass spectrometer and is also an important part of the control system of the whole instrument.