中文摘要：

以STC12C5A60S2单片机为控制核心，设计并制作一台闸门时间为1s的数字频率计，可实现信号的频率、周期、占空比和时间间隔等参数的测量。系统能够测量的正弦信号频率范围为1Hz-130MHz，被测信号电压有效值范围为10mV～1V，测量精度达0．01％。系统设计及测试中呈现出三大优势：第一，在信号前级整形时采用轨对轨高速比较器TLV3501，延迟时间为4．5ns，小信号比较效果非常好，可将微弱的交流电压转换为TTL电平。频率测量可以达到指标要求；第二，信号源输出信号经过衰减器，可以达到测量小电压的指标要求；第三，在高频干扰的滤除方面措施采取得当，方便后续分频等环节处理。系统能满足实际测量要求，结构紧凑，效果良好。

英文摘要：

This system designed and manufactured a digital frequency meter based on STC12C5A60S2 singlechip MCU whose gate time is 1 second. The measurement of the frequency, period, duty cycle, time-interval of a signal can achieved. In fact, the measured band width is from 1 Hz to 130 MHz. The measured voltage rms value is from 10 mV to 1 V. Tests show that the measurement accuracy is 0.01%. The design shows three striking advantages. Firstly, the adoption of TLV3501 chip at preliminary waveform shaping stage can achieve the delay time of 4.5 ns, which proves the desirable effects of the weak signaling. Weak alternating currents can be switched to TYL level and the frequency measurement meet the corresponding requirements. Secondly, output signal can meet the requirement of measuring small voltages through attenuator. Thridly, proper measures are taken to filter the the high frequency signals to facilitate the follow-up process such as frequency division. The system is compactly built and can meet the practical measuring needs and proves to be effective.