Measuring Air Flow – Made Easy
A sonic anemometer is a device that measures air velocity using sound. A speaker on one end of the device emits a ‘ping’, and a sensor waits for the ping to arrive. If the air is not moving, then the delay between ‘pinging’ and ‘receiving’ is always the same (kinda).
If the air is moving from the sensor toward the emitter, then the delay gets longer since the ping is traveling upstream. Conversely, if the air is moving from the emitter toward the sensor, then the delay gets shorter since the ping is traveling downstream.
I built this anemometer to measure airflow rates of various small fans.
All you need is an Arduino, an HC-SR04 ultrasonic distance sensor, a piece of 3/4″ PVC conduit, and a 3D printer. The 3D print file and firmware is available on Github.