基于FPGA的高精度频率测量系统设计及应用

Design and Application of High-Precision Frequency Measurement System Based on FPGA

针对石英晶体微天平(QCM)传感器应用于气体检测需要高精度频率测量,设计了一种基于FPGA的高精度频率测量系统;提出了一种基于锁相环的等精度频率测量方法,降低了频率测量的理论相对误差;设计了频率测量系统整体架构,根据整体架构完成了基于FPGA的高精度频率测量系统硬件电路,设计了一种包括频率测量、通讯、程序固化等模块的嵌入式软件,实现了基于FPGA的高精度频率测量系统的集成,并将其应用于基于QCM的二氧化碳气体浓度检测;实验结果表明,频率系统测量绝对误差不超过0.35 Hz,误差平均值为0.268 Hz,最大相对误差为3.5×10^(-8),频率测量分辨率可以达到0.1 Hz,该系统测量误差较小,稳定性较好,在基于QCM的二氧化碳气体浓度检测中具有较好的应用前景。

Aimed at the need that quartz crystal microbalance(QCM)sensors are used to measure high-precision frequency in gas detection,a high-precision frequency measurement system based on field programmable gate array(FPGA)is designed.An equal-precision frequency measurement method based on phase-locked loop is proposed to reduce the theoretical relative error of frequency measurement,and design the overall architecture of the frequency measurement system.According to this architecture,the hardware circuit of the high-precision frequency measurement system based on FPGA is completed.The embedded software is also designed,which includes the modules of frequency measurement,communication,and firmware programming.The integration of the high-precision frequency measurement system based on FPGA is achieved,which is applied in the QCM-based carbon dioxide gas concentration detection.Experimental results show that the absolute error of the frequency system measurement does not exceed 0.35 Hz,with an average error of 0.268 Hz and a maximum relative error of 3.5×10^(-8).The frequency measurement resolution can reach 0.1 Hz.The system has the advantages of low measurement error,good stability,and better application prospect in the QCM-based carbon dioxide concentration detection.