Study On Quartz Crystal Viscosity Sensor And Its Frequency Characteristic

Viscosity is a kind of measurement, which is used to reflect flow resistance inthe liquid. Moreover, viscosity is also an important parameter, which showscharacteristic of the liquid. Now, viscosity measurement is used widely in some field,such as petroleum industry, chemical, weave, national defence, and medicine. Forexample, in the medicine field, viscosity measurement of blood and physiology liquidis becoming an important diagnosis measure of difficult disease, such as heart,encephalon and blood vessel malady. On industry, viscosity, which has a similar totemperature, pressure, is an important parameter in general industry productionprocess. People depend on these parameters to monitor and control product line. Thisis significant, which enhances product quality, ensures production safety, mendsoperation craft, improves production condition.The traditional viscosity meters have a lot of kinds, such as tubule viscositymeter, falling viscosity meter, circumgyrate viscosity meter. But, these viscositymeters have difficulty in production and request the rigorous testing condition. Inaddition, they have high price and request long testing time.It had been found by research that the frequency response of quartz crystal andequivalent impedance had good relativity with the viscosity of liquid in the givenareas. In this paper, the contrary piezoelectricity of quartz crystal is used as theprinciple to converts viscosity signal to electric signal as output in designing the newquartz crystal viscosity sensor. Compared with the traditional measuring method, thissensor has many merits. First, it is convenient to connect with the computer, so as tocontrol automatically. Second, it can be monitored momently because its goodtime-stability. Third, the configuration of the sensor has been predigested, so it isconvenient to take, and this also debases its cost.In this paper, mechanism of quartz crystal viscosity sensor in liquid medium isdiscussed and used as the principle in designing viscosity sensor. After that, theoscillatory characteristic of quartz crystal in liquid medium is analyzed theoretically.Based on the above analyses, the sensor structure is designed. Moreover, frequencydrive circuit of quartz crystal has been finished and debugged, including SCMAT89C52, Direct Digital Frequency Synthesizer (DDS), the interface circuit ofkeyboard and Liquid Crystal Display (LCD), high frequency magnifying circuit.Finally, the sensor is tested.A series of experiments has proved that there is high sensitivity in resonancefrequency of quartz crystal between the output voltage of the sensor and the viscosityof liquid. There is good relativity between resonance frequency of quartz crystal andviscosity of liquid. It indicates that prompting response quartz crystal viscosity sensoroffers a new method in measuring liquid viscosity.