This study was conducted to expand the measurement range of a continuous wave ultrasonic
anemometer (CWUA) that uses phase difference measurement. A CWUA has a narrower
measurement range than conventional ultrasonic anemometers because it can
measure the phase difference up to the half-cycle of the used ultrasonic signals. In this
study, a method of expanding the measurable range of the phase difference using a phase
delay circuit and a frequency divider was developed. Through experiments, it was found
that this method doubled or quadrupled the measurement range when the method was
used. Furthermore, an algorithm for determining the validity of the measurement data
by comparing them with the previous data was implemented with a wind velocity measurement
error of less than ±1 ls to solve the problem caused by the use of the frequency
divider and to produce a stable measurement system.