Anemometer with three-dimensional directionality for detection of very low speed air flow and acoustic particle velocity detecting capability

We develop a micro-fabricated anemometer with three-dimensional directionality based on thermal Thomas flowmeter principle, which is capable of measuring very low airflow speed. This sensor has three layers of resistive platinum beams. Experiments on speed lower than 200 mm/s are conducted, showing acceptable repeatability and obvious directionality. The speed of airflow is tested with the volumetric flow rate. To further explore its potential, we expose it to acoustic plane waves of frequency range from 200 Hz to 1.38 kHz in a standing wave tube, showing consistent planar directivity of figure of eight. Velocity sensitivity at 1 kHz and 120 dBC measures 4.4 mV·s/m, with relative sensitivity of 27.0 dB.