The core of ultrasonic wind speed and direction measurement

Most of the modern meteorological monitoring stations are developing in the direction of all-day unattended operation. The establishment of automatic meteorological monitoring stations is in urgent need of more accurate and maintenance-free automatic monitoring instruments, including wind anemometers to meet this condition. Traditional mechanical wind anemometers are characterized by rotating parts and easy wear and tear. The mechanical structure can be damaged by bad weather. Sand, dust, salt spray can also corrode it. At the same time, mechanical anemometers also have a start-up wind speed due to friction. The wind speed below the starting value will not be able to drive the propeller or wind cup to rotate. So the breeze below the starting wind speed cannot be measured by mechanical anemometer. In order to overcome the inherent shortcomings of the traditional wind cup anemometer, a new ultrasonic wind speed anemometer has emerged. The ultrasonic wind speed measurement technology does not require any moving mechanical parts in the measuring instrument but replaces them with multiple ultrasonic sensors. The lower limit of the theoretical measurable wind speed range is 0, with no start-up wind speed; the upper limit of the wind speed can vary with the sensor spacing.

The heart of ultrasonic wind speed and direction measurements is the propagation time of ultrasonic waves through the air, known as the fly-through time. The time it takes for ultrasonic waves to travel from one probe to another is related to the wind speed and ultrasonic path. A tailwind causes the propagation time of the ultrasonic signal to increase, while a headwind causes it to decrease. If the wind speed is equal to zero the signals are sent in equal time in both directions. If wind speed is measured in two unrelated directions at the same time, the wind speed and direction can be derived from a combination of trigonometry.