中文摘要：

根据谐振腔的谐振频率随腔内空气介电常数变化发生偏移这一特性，研制了基于微波谐振腔的汽轮机蒸汽湿度测量系统。设计了自动频率跟踪模块，利用单片机来控制压控振荡器VCO的输出频率。保证了VCO的输出频率与谐振腔的谐振频率一致，减小了频率跟踪的时延，从而提高了整个测湿系统的测量精度。在频率测量模块中，采用多周期同步测量与量化延迟法相结合的高精度频率测量方法，使测量分辨率达到了0．1Hz，满足系统的要求。利用此系统对湿空气环境进行了测量，分析了测量结果和理论结果间的误差，二者表现出较好的一致性．

英文摘要：

According to the characteristic that the resonant frequency of the resonant cavity shifted with the change of air permittivity, this paper introduces a steam turbine humidity measurement system based on microwave cavity. It discusses an automatic frequency-tracing module, which using MCU to control the output frequency of VCO to minimize the delay of frequency tracking so as to improve the measurement accuracy of the system. In frequency measurement module, a method of high accuracy frequency measurement is introduced combining multi-cycle synchronization and quantization delay, and the resolution can reach 0.1 Hz satisfying the system requirement. A measurement on moist environment has been made using this system and the experimental data and theoretical value are compared and analyzed. It shows that the measured results are basically identical with the theoretical results.