The Research And Implementation Of The Dissipative Factor Detection System Of The Quartz Crystal Microbalance (QCM)

Quartz Crystal Microbalance(QCM)is a resonant type mass sensor,which used the sensitive film on the surface of the crystal as the sensitive element and the AT cut quartz crystal as the energy conversion element.The development of the sensor had great significance to the fields of biology,medicine,environmental science and so on.For the purpose to research the detection of the QCM's dissipation factor,a design of the QCM's dissipation factor detection system was put forward,which took the advantage of the high speed and the ability to operate in parallel of FPGA.The work of research of this thesis mainly includes:(1)Aimed at the effects,which was caused by the shunt capacitance of the QCM,to the phase when it was working,a compensating circuit of this kind of capacitance was designed,and on this basis it was adjusted to enhance the ability of the QCM to control the circuit.(2)Aimed at the dynamic range indication and the disability of measuring equivalent impedance of the QCM,an auto-excitation amplifier circuit controlled by AGC was designed,which made the QCM oscilliate stably in gaseous phase and liquid phase,with the application of three order Butterworth LPF.(3)A circuit which can gain the signal of QCM's Dissipation parameter was designed,and the collection,saving and trasmission of the signal of parameter were realized based on FPGA technology,and the logic modules of system operation were also designed.(4)The whole board of the designed QCM's dissipation factor detection system was performed logic debugging and experimental verification,and the experiment of the detection of the dissipation factor of the QCM in different fluid was completed with combining the upper computer software.