A microprocessor based, three axes, ultrasonic anemometer

Abstract

The authors describe a microprocessor based ultrasonic anemometer able to measure the wind velocity vector by means of three pairs of piezoelectric transducers (250 kHz resonant frequency) placed along three orthogonal aces. The measurement principle is based on the inverse transit time difference (ITTD) measurement of ultrasonic pulses on a known path L, upstream and downstream of the air flow. This method avoids the need for temperature compensation hardware in a wide temperature range. The instrument is fully controlled by means of an MC 146805 microprocessor. Wind tunnel calibration tests showed an accuracy better than a few percent of FS in a temperature range from -20 to +70 degrees C, with a negligible dead band.