Here, t is the ultrasonic travel time of each path, v is the
ultrasonic velocity and u is the wind velocity.
Previous systems using the time-sharing method
were not affected by the temperature of the wind
when applying Eqs. (2) and (3) and this removed the v
factor which is sensitive to temperature [8,9]. However,
in this proposed system, the transit time of the ultrasonic
signals is not measured when there is no wind.
Therefore, this study calibrates when the wind velocity
is calculated with a temperature sensor. Fig. 2 is the
result of calculating the change of delay time by
temperature in the designed system. The variation is small
in the low wind velocity. However, the change is huge
in the case of high wind velocity, and hence compensation
is required.