Aiming at problem that using ultrasonic wave Doppler method to measure flow

at small flow velocity frequency difference is not easy to obtain

and signal processing algorithm is complex

an improved ultrasonic wave flow detection method is presented.The driven voltage improved adopts ultrasonic wave driven circuit using medium frequency transformer as core.In ultrasonic wave receiving circuit design

received small signal is processed with frequency selection

amplification and filtering

impedance matching

linear converts sion between frequency difference and DC control voltage is realized by phase-locked loop.Aiming at electromagnetic compatibility problems of the instrument

power Conducted interference which influences the instrument work correctly is tested

EMC rectification method is given.Test result shows that because it uses the AC power source filter

maximum relative error of flow is controlled within 6 %.