A hybrid TOF Measurement Method for Ultrasonic Gas Flowmetry Based on Triple Zero-crossing Detection and Cross Correlation

Abstract

In transit-time ultrasonic gas flowmeters, the measurement accuracy of gas flow relies heavily on the precise determination of the time of flight (TOF). Traditional TOF measurement methods, such as the threshold method, cross-correlation method (CC), and model-based approach, each have limitations: the threshold method is sensitive to waveform distortion and noise, the CC method suffers from limited temporal resolution due to sampling frequency constraints, and model-based method requires excessive computational effort. To address these challenges, this study proposes a novel hybrid TOF measurement method that combines triple zero-crossing detection (T-ZCD) with cross-correlation. T-ZCD technique enhances temporal resolution and noise immunity at low flow rates through triple sampling and averaging, while the CC method improves robustness at high flow rates. A six-channel experimental test rig was constructed to validate the proposed hybrid TOF measurement method. Experimental results demonstrate that the proposed method achieves superior accuracy and repeatability in TOF estimation compared to conventional approaches, leading to significant improvements in flow measurement precision.