Furthermore, it can implement sampling rates of several
hundred Hz to several tens of thousands of Hz, because it
measures the phase difference between the ultrasonic signals
that it continuously receives. High reliability and
accuracy can be achieved by adding efficient signal processing
of the data that are acquired at high sampling rates.
The measurable phase difference is limited, however, to
the half-cycle of the used ultrasonic signals due to the
characteristic of the operating principle. The measurement
range can be expanded by using low-frequency signals, but
the effect of external noise increases as the frequency approaches
the audio frequency and it is difficult to increase
the measurement range to the level of the measurement
range of the commercial ultrasonic anemometer.
In this study, to achieve a wide measurement range
using the low-frequency signal of 40 kHz, which is widely
used, a receiving circuit was designed. Offset phase differences
are caused by the minute distance difference between
the transmitter and each receiver, including offset
of IC components in the receiving circuit. The measurement
range of the ultrasonic anemometer is increased by
expanding the measurable phase difference through removal
of the offset phase differences and dividing the frequency
of the received signals.