Uncertainties Propagation Study of the Transit Time Methods in Ultrasonic Anemometers

The fluids speed measurement, particularly the air speed measurement is very important for industrial and laboratory applications. The ultrasonic method is among the most common methods used for determining the air speed. The basic principle to measure a fluid speed, using an ultrasonic transducer, is based on the modification of the apparent propagation speed of an ultrasonic signal caused by the fluid movement. Particularly, the method based on the Transit Time, which can use the techniques of Phase Difference and Time Difference, is one of the most used. In this work we carry on a comparative study of the uncertainty propagation employing these techniques in ultrasonic anemometers for determining the air speed.