Difference between Mechanical and Ultrasonic Anemometers

At present, there are two types of equipment for monitoring wind speed and wind direction: one is an anemometer with a mechanical structure, and the other is an anemometer with ultrasonic measurement. These two types of wind speed and direction sensors are two common devices in daily life. What are the similarities and differences between the two, whether there is an accuracy problem, and how to choose.
The mechanical wind speed and direction sensor is not one, divided into wind speed sensor and wind direction sensor:

Wind speed sensor
The mechanical structure of the wind speed sensor is a sensor that can continuously measure the wind speed and air volume (air volume = wind speed × cross-sectional area). The more common wind speed sensor is the wind cup wind speed sensor. The measuring part is composed of three or four hemispherical wind cups. The wind cups are installed on the rotating bracket on the vertical ground at an equal angle along one direction.

Wind direction sensor
The wind direction sensor detects and senses the wind direction information of the outside world with the rotation of the wind direction arrow, and transmits it to the coaxial code disc, and outputs a physical device corresponding to the relevant wind direction value. Its main body adopts the mechanical structure of the wind vane. When the wind blows to the tail of the tail of the wind vane, the arrow of the wind vane will point to the direction of the wind blowing. In order to maintain sensitivity to direction, different internal mechanisms are also used to identify the direction of the wind anemometers.

Ultrasonic anemometer
The working principle of ultrasonic is to use the ultrasonic time difference method to realize the measurement of wind speed and direction. Because of the speed of sound in the air, it will be superimposed with the speed of the airflow in the wind direction. If the ultrasonic wave travels in the same direction as the wind, its speed will increase. Conversely, if the propagation direction of the ultrasonic wave is opposite to the wind direction, its speed will be slower. Therefore, under fixed detection conditions, the speed of ultrasonic propagation in the air can correspond to the wind speed function. The precise wind speed and direction can be obtained by calculation. Since the speed of a sound wave is greatly affected by temperature as it travels through the air, the anemometer detects two opposite directions on the two channels, so the effect of temperature on the speed of the sound wave is negligible.

To sum up, since the wind direction sensor and wind speed sensor are both mechanically designed and have rotating parts, the minimum wind speed before monitoring is the starting condition. If the wind speed is lower than the starting value, the propeller or wind cup cannot be driven to rotate. Therefore, monitoring cannot be performed. On the other hand, it is an ultrasonic anemometer. The biggest feature of this device is that it can work even at zero wind speed without starting wind speed, and it is different from the mechanical wind speed and wind direction, which requires two devices. Ultrasonic integrates two types of monitoring. The method is integrated, with simultaneous detection and simultaneous output.

With the rapid development of the Internet of Things, the demand for the accuracy of monitoring meteorological elements is increasing. The use of ultrasonic wind speed and direction sensors can well overcome the inherent defects of mechanical wind speed and direction, so it can work normally all day and for a long time. In the future, the cost can be reduced, and it will be a strong substitute for mechanical anemometers.

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