为精准测量信号频率等参数,设计了一种以STC89C52RC单片机为控制核心、由三极管3DG120、施密特触发器74HC14和分频器74HC4040等构成信号处理电路,可以测量信号频率、周期、脉冲宽度等参数的多功能数字频率计.该频率计通过RS232串口将单片机测量的数据传送至上位机,利用上位机软件集中显示所测信号的频率、周期、脉宽、占空比等各参数测量值并描绘出所测信号波形,给出了单元模块设计电路和配套的软件设计,并提出小信号测量时抗干扰的一些办法.实验表明,系统结构简单,是对电子计数器多功能和多用途的扩展型设计和研究,频率测量误差低于0.1％,达到设计技术指标,具有良好的人机交互性,其中信号频率测量范围为1～50 MHz,可测小信号,幅值低于0.5 mV,能满足实际测量要求.%To achieve the purpose of precision measuring signal frequency, we design a simple multi-function digital frequency meter with the fuction of measuring signal frequency, cycle, pulse width and duty ratio, using STC89C52 single-chip computer as the core controller, triode 3DG120, 74HC14 chip and 74HC4040 chip as the signal processing circuit, and present the unit module circuit and matching software. We put forward some anti-interference measures for the small-signal measurement. Experiments show that the system has achieved the design object, including its frequency measurement range for 1 ~ 50 MHz. The measuring error is less than 0. 1 % and the measuring small signal amplitude can be lower than 0. 5 mV. It meets the testing requirements.
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