Airflow rate measurement using a set of sound radiator and sound detector in a sub-pipe

We report a novel method by which to measure airflow rate. Unlike the sound velocity differential method used in most ultrasonic flow meters, the proposed method is not overly sensitive to the fluid temperature because the flow rate is evaluated based on the magnitude of sound pressure. The measurement system is composed of a main pipe and a small sub-pipe connected to the main pipe. A dog whistle, used as a sound radiator, generates ultrasonic waves, the sound pressure of which is detected by a microphone. The dog whistle has been supersensitized by bias airflow. A data-acquisition and processing system controlled by a PC was used in the experiments to measure various types of data. The results of these experiments reveal that the proposed method has a high feasibility. The advantages of the proposed method are as follows: the effect of changes in the fluid temperature is slight, the low-pressure gas flow rate is measurable, and the electronic circuit is comparatively simple.