多功能数字频率计的设计与研究

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1~50MHz，可测小信号,幅值低于0.5 mV，能满足实际测量要求。

Design and Research of Multifunctional Digital Frequency-Counter

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.