Flight time measuring method and system of ring buzzing method ultrasonic flowmeter

The invention discloses a flight time measuring method and system of a ring buzzing method ultrasonic flowmeter. The method comprises the following steps: firstly, determining an amplification factor of an echo circuit and a first threshold voltage; secondly, comparing the number of pulses after echo processing to determine whether the pulse signal can be used as an excitation signal measured by a ring singing method or not; after the number of times of cyclic measurement of the ring singing method is reached, comparing an echo signal obtained by final amplification and filtering with a first threshold voltage and a second threshold voltage, and determining three time points; and finally, judging the relation of the three time points, if a rule is met, obtaining the flight time through a time measuring circuit, otherwise, re-measuring. According to the invention, by changing the amplification factor of the echo circuit in real time, the consistency adjustment of the peak value of the echo signal is realized,