Design Of Data Acquisition Circuit Of Quadrupole Mass Spectrometer

In the early days, people usually record the mass spectrometry data through the photography when using the mass spectrometry. With the development of the computer technology, the computer has been widely used in the mass spectrometry analysis. The mass spectrometry data acquisition circuit has become an important part of the mass spectrometer. The purpose of this thesis is to research and design a kind of data acquisition circuit.According to the request of the thesis a data acquisition circuit of a quadrupole mass spectrometer has been designed and the mass spectrometric analysis software along with control program is also been developed. The Mass spectrometry data acquisition circuit can be divided into the following several parts, namely:the scanning control circuit, Ⅳ conversion circuit, filter circuit, data acquisition and control circuit, transmission and power supply circuit. A low noise and high precision 16 bits ADC chip had been used In the design of the scanning control circuit which provides a low noise and linear scanning voltage for the mass spectrometer and the fast scanning speed can reach lms/amu. The IV conversion circuit includes three feedback resistances and an operational amplifier. The data acquisition system at last can receive the signal range of 7 orders of magnitude by changing the feedback resistance in the circuit. Through the mass spectrometry analysis of software and control software, the thesis have realized the map drawing, mass data processing and storage, IT curve drawing and other functions.The design of Quadrupole mass spectrometer data acquisition circuit in this thesis has the characteristics of fast speed, low noise and wide dynamic range of input signal. When the feedback resistance used in cross IV switching circuit is 108Ω, the peak to peak value of noise can be controlled at about 30μV. The design creates a good condition for the trace substances Analysis.