石英谐振式露点传感器的理论与实验研究

The project is aimed to explore dew point measurement which is based on quartz crystal resonance. It applies the quartz crystal micro balances (QCM) technique with semiconductor refrigeration. Through the active temperature control, condensation is produced on the surface of OCM and then an obvious mutation appears in its added mass. Thus the quality - frequency effect will produce obvious changes in natural frequency of the quartz crystal, thereby identifying and measuring the dew point. The project will use vibration theory of the quartz crystal to carry out research in physical properties of the humidity sensitive unit formed by combination of the quartz crystal and semiconductor refrigerator. The research methods include the theoretical modeling and numerical simulation calculation, as well as experimental verification. Intensive study will be conducted in investigating mechanical properties, electrical properties and thermal characteristics of the unit and revealing its internal change mechanism and signal conversion regularity triggered by electricity, heat, wet and etc., thereby developing design methods for optimizing its structure. Furthermore, through observations of rapid changes in the resonance frequency generated under the temperature when the dew point is forming and multi-parameter coupling characteristics of the humidity sensitive unit, this project will use time-frequency analysis, decoupling control theory and experimental research to find ways of estimating the instantaneous frequency and quick dew point recognition. Double closed loop control ways of tracking the resonance frequency under the double incentives of electricity and heat and testing dew point temperature of quartz crystals will be also developed. Ultimately, our study will provide theoretical and experimental basis for the design of quartz resonant dew point sensors.

探索基于石英晶体谐振敏感激励的露点测量方法,将石英晶体微天平(QCM)技术与半导体制冷技术结合，通过主动温控在QCM表面产生凝露，使得QCM表面附加质量明显突变，由QCM的质量-频率效应导致石英晶体固有频率的明显变化,由此测量露点。本项目将结合石英晶体振动理论对石英晶体与半导体制冷器粘贴组合后所形成的湿敏元件的物理特性进行研究,通过理论建模、数值仿真计算与实验验证相结合的方式，深入研究该湿敏元件的机械特性、电特性和热特性，揭示其在电、热、湿等激励下的内在变化机理与信号转换规律，给出其结构优化设计方法；针对露点温度附近谐振频率快速变化和该湿敏元件多参数耦合的特点，结合时频分析、解耦控制理论和实验研究，寻求瞬时频率估计和露点频率快速识别方法，探索电、热双激励下的谐振频率跟踪和石英晶体表面露点温度跟踪的双闭环控制方法。通过本项目的研究将为石英谐振式露点传感器的的设计提供理论依据与实验基础。

项目研究了基于QCM的露点测量方法，将石英晶体微天平技术与半导体制冷技术相结合，采用主动控温的方式获取结露现象，并通过检测QCM频率突变时刻的温度实现露点测量，获得了较高的测量精度。项目结合QCM振动理论对QCM与半导体制冷器组成的湿敏单元的物理特性进行了研究，建立了湿敏单元的有限元模型，对其在电、热激励下内在的变化机理与信号转换规律进行了分析，并在此基础上设计了电极传热型和对称固定型QCM露点传感器结构，有效提高了传感器的热传导效率和稳定性，为露点的快速稳定测量提供了良好的条件；将QCM露点测量原理与其测量系统相结合，分析了测量过程中QCM温频特性对露点识别的影响，设计了双通道露点传感器结构，去除了温度变化对测量结果的影响，提高了露点识别的精度；研究了QCM驱动方法和露点识别方法，在此基础上设计了既能维持QCM稳定振荡又能实现QCM温度跟踪的双闭环控制方法，实现了露点测量的智能化，为QCM露点传感器的广泛应用奠定了良好的基础。