The Study On The Technology Of Microbial Sensor Based On Quartz Crystal Resonator

Quartz crystal resonator is a kind of new type sensor based on quartz crystal basement which was formed by different angle cutting.And this technology has become the source of vibration by using the inverse piezoelectric effect that the crystal having itselfly.When the crystal was connected to the solution forming the resonant circuit with the other reactance elements,the growth state of the solution microorganism was detected by the frequency response of the crystal to the concentration of the electrolyte caused by the microbial metabolism in the solution,thus forming a kind of new biological electrochemical sensor.Firstly,this thesis introduces the current development of quartz crystal standard of thermostat tic crystal at home and abroad.The thesis also introduces the advantages and disadvantages of several common types of cutting quartz crystal.Based on the selected cutting type,the thesis introduces and analyzes the parallel resonance circuit,and discusses the oscillating balance of requirements detaily.In this thesis,quartz crystal resonators are used to detect changes based on the principle that it has a sensitive frequency response to parameters of electrolyte solution in medium.In this thesis,the tandem piezoelectric sensor model is used to complete the overall design of the resonator.In the design of the oscillating stage circuit and the matching impedance network of the resonator,it is necessary to take reasonable account of the influence factors of the quartz crystal itself to ensure the stability of resonator operation.Theory of resonator's noise is discussed in detail.This thesis firstly analyzes the general noise amplifier model.Nextly,the noise of the general-purpose configuration transistor amplifying circuit which used in this paper is analyzed and equivalent to the corresponding transistor En-In model.On this basis,the equivalent circuit of quartz crystal is connected to the En-In model of the amplifier circuit to discuss the noise.Then,discussing the applicability of the strongest interest noise model detailly,by analysing the main factors(noise)caused by the short-term stability of the resonator,the design principle of the low-noise crystal resonator and the theoretical guidance for the design of the resonator with high stability are summarized in this thesis.Next,based on the discussion of design principles,this paper completes the design of the vibration level cole peet's circuit,amplifier stage circuit and the feedback loop,and designs a stable and controllable constant temperature box according to the strict requirements of quartz crystal resonators to external environment,finally got a good quartz crystal resonance sensor which has short-term frequency stability.Through testing the stability of the resonator,aftering the stage of amplifier circuit,the resonator displays a sine wave which's frequency is 9 MHz and standard amplitude is 1.8V on the oscilloscope.In the case of the external environment remains unchanged,short-term frequency stability can be stabilized at ±3Hz,and completing the stability of the verification.Finally,the influence factors of quartz crystal resonator are studied continuely through experiments,and the expected influencing factors are set to a single variable for experimentation.Resonant parameters of quartz resonator is not only related to microbe solution of electric parameters,but also the excitation signal,temperature,loop electric parameters et;all of thses will have an influence on the resonator,especially the temperature parameter for the quartz crystal parameters are typically sensitive to it.Excitation signal must be given as a stable DC signal,and ensure the stability of the external environment in which the sensor is located,at the same time,It is necessary to design feedback circuit with the resonator in the need for compensation to ensure the stability of the resonator.