Time difference determination method and device based on ultrasonic sensor

The invention belongs to the technical field of ultrasonic gas flow detection, and particularly relates to a time difference determination method and device based on an ultrasonic sensor. The method comprises the following steps: firstly, transmitting a phase modulation signal for driving a transmitting transducer; sampling an output signal of a receiving transducer, and performing envelope extraction to obtain a downstream envelope and a countercurrent envelope; all minimum values in the downstream envelope line and the countercurrent envelope line are found, real extreme values caused by phase modulation on the downstream envelope line and the countercurrent envelope line are found, and the real extreme values comprise the real minimum value and/or the real maximum value; and finally, according to the real extreme values of the downstream envelope and the countercurrent envelope, the ultrasonic signal time difference is determined. According to the method, the corresponding time information is obtained by u