High Sensitivity, Miniature, Full 2-D Anemometer Based on MEMS Hot-Film Sensors

High-resolution airflow monitoring in urban environments requires deployment of a large number of anemometers with precise measurement capability of both wind speed and direction in two or three dimensions. Existing sensors are too expensive and/or bulky for this application. It is known that microelectromechanical systems (MEMS) sensor-based anemometers can be low in cost for mass production. And due to its ultra-thin filaments and fine structure, a MEMS-based hot-film sensor also has the potential to outperform traditional hot-wire or hot-film sensors. Existing MEMS-based anemometers that integrate multiple sensing elements on a chip for detection of airflow speed and direction show low sensitivity due to their in-plane structure, which cannot harvest wind energy efficiently. In this paper, we develop an anemometer having a probe structure mounted with three MEMS-based hot-film sensor chips, which can detect both airflow speed and direction with high sensitivity while keeping a compact size for the probe (6-mm diameter). The prototype anemometer is calibrated for detection of wind speed with accuracy of 3.6% [relative root mean square (RMS) error] in a range of 0.1-10 m/s, and wind direction from 0° to 360°, with an accuracy of 1.20 degree (RMS error). We field-test the MEMS based 2-D anemometer at urban wind monitoring points and the results agree well with monitoring data of nearby commercial 2-D ultrasonic anemometers.