Feature Wave Recognition-Based Signal Processing Method for Transit-Time Ultrasonic Flowmeter

In order to improve the measuring precision and stability of transit-time ultrasonic flowmeter as well as the locating accuracy of datum point for ultrasonic received signal, a feature wave recognition-based signal processing method is proposed in this study, which derives from analyzing the cause of errors in conventional threshold approach. By introducing a phase-shifted pulse into the ultrasonic excitation one, a feature wave with different period and phase is consequently produced in the ultrasonic received signal and recognized using a high-precision TDC chip according to the period of the received signal at first. Then the datum point of the received signal is accurately located with regard to the relationship between the position of feature wave and the initial position of the received signal so that the transit time of ultrasonic signal is finally measured. The following experiments focusing on a real-world problem demonstrate that the proposed method can effectively reduce the measurement errors caused by the amplitude change of the received signal. Such an approach is greatly beneficial for improving the precision of measurement along with the stability of the ultrasonic flowmeter.