Ultrasonic anemometry from very to low to high air flow speeds using a cw or long pulse ultrasonic wave

S. Dixon, D. Greenshields, Z. Li, W. Sun, L. D. Smith

Abstract

Ultrasonic anemometers have a wide dynamic range, no moving parts and potentially high accuracies for measuring wind speed, but can also be used for indoor air flow monitoring. Some designs of ultrasonic anemometer already use flexural ultrasonic transducers (FUTs)- a sensor that is used extensively in car parking sensors as they are low cost, robust and reliable. Ultrasonic anemometers often use a method called transit time difference, where the different transit time generally with or against the air flow gives rise to a transit time difference, that can be used to calculate air flow speed. In most conventional ultrasonic anemometers, each transducer in a pair is pulsed in turn, with one generating whilst the other detects, and then the roles are reversed by multiplexing. The ADC captured signals and are processed using cross-correlation (or similar). Arranging pairs of transducers at different angles facilitates 2D and 3D measurements of air flow speed - the most common being 2D anemometers. Both air flow speed and direction (velocity) can be calculated. Challenges with this approach include that ADC and signal processing needed are relatively power-hungry and expensive.

Keywords

Ultrasonic anemometer; Ventilation monitoring

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IMEKO-TC9-2019-059.pdf

DOI

10.21014/tc9-2022.059

IMEKO TC

TC9 - Flow Measurement

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