Ultrasonic Transit Time Measurement Based on Frequency Doubling Technique

Ultrasonic gas flowmeters are widely adopted in industrial applications due to their advantageous features, such as zero pressure loss and easy installation. However, the conventional threshold detection method, despite its real-time performance, suffers from degraded accuracy caused by circuit and pipeline noise, which introduces fluctuations in echo signal amplitude and phase. This paper theoretically demonstrates that doubling the ultrasonic signal frequency steepens the rising edge slope of the echo signal, reducing the time interval during which random noise affects comparator output. Experimental results validate that the proposed technique achieves a 29.23% reduction in the mean measurement error of transit time compared to traditional methods, particularly showing pronounced improvements in low-flow scenarios.