A simple and easy-implemented time-of-flight determination method for liquid ultrasonic flow meters based on ultrasonic signal onset detection and multiple-zero-crossing technique

Determination of time-of-flight (TOF) is crucially important in liquid ultrasonic flow meters. There are some deficiencies of previous TOF detection methods in practical applications. Inspired by our last work and the knowledge of clustering algorithms, we proposed a TOF determination method based on ultrasonic signal onset (USO) detection and multiple-zero-crossing technique to solve cycle-skip problem caused by waveform change. This method categorizes the ultrasonic and the noise signal, and identifies the rough position of USO. A time value from the obtained zero-crossing time values is selected as the TOF. The main advantage of the proposed method is the high insensitivity towards waveform change, i.e., the effect of amplitude characteristics change on TOF detection is negligible. Numerical experiments were done to evaluate the performance of the proposed method and its anti-noise ability. Experimental validation on a liquid ultrasonic flow meter showed the proposed method is capable of obtaining the accurate TOF.