Abstract:In order to measure the frequency of a sinusoidal signal in high precision, the article designs a digit frequency meter based on FPGA (field programmable gate array). Besides measuring frequency, the device can also measure the time interval of two square signals and the duty ratio of a pulse signal.With FPGA and MCU (micro control unit) as the kernel, the meter adopts the method called ‘Parallel MultiWays Counting Method’ to realize the high precise measurement. Specifically, signals would input FPGA after high frequency amplification module and high frequency comparing module. And then signals would be divided into multiways to decrease frequency by different times and be counted synchronously. Finally, MCU would select the mostaccurate result and get the final result after computing. After the test, the meter can measure the frequency of a sinusoidal signal from 1 Hz to 199 MHz and from 10 mVrms to 1 Vrms with the relative error not above 0.0001%; the meter can measure the time interval of two square signals from 50 mV to 1 V and from 100 Hz to 1 MHz with the relative error not above 1%; the meter can measure the duty ratio of a pulse signal from 50 mV to 1 V and from 1 Hz to 5 MHz with the relative error not above 1%. Therefore, the meter has thefeature of high precision, wide frequency range and wide amplitude.