Measurement principle of ultrasonic wind measuring instrument

Wind is closely related to people's lives. Accurately and timely obtaining wind information has great guiding significance in crop cultivation, industrial wind tunnel detection, meteorological monitoring, ship navigation, wind power generation, and other aspects. Compared to traditional mechanical anemometers, ultrasonic anemometers adopt a solid-state design without rotating parts, and there are no faults or measurement errors caused by wear and tear. They are very suitable for use in harsh weather conditions, and in principle, the starting wind speed is 0 with no upper limit for measurement. They are an ideal instrument for measuring wind speed and direction, and have a wide range of application prospects.

    At present, in the research of ultrasonic wind measurement in domestic scientific research institutions, ultrasonic transducers with resonant frequencies of around 40 kHz and 200 kHz are mainly used. Among them, systems made with 40kHz ultrasonic transducers have lower accuracy, and often improve measurement accuracy by using high-frequency processors such as ARM and DSP and increasing probe spacing. This inevitably leads to larger instrument structures and bulky shapes. Using ultrasound transducers with higher center frequencies means higher hardware configuration requirements for the processor, which undoubtedly increases the cost of the system. Starting from reducing system costs and simplifying signal processing algorithms, the front-end circuit of the ultrasonic wind measurement system was designed in the article. The use of ICCL7667 and pulse transformer for joint boosting at the driving end improves the consistency of the four driving signals, and breaks through the traditional method of extracting the envelope of the received signal. A corresponding peak detection circuit is designed to highlight the peak point of the received signal, and a simple and feasible peak time determination method is proposed. The detection signal reduces the impact of pulse interference in the received signal and has good stability.

Measurement principle of ultrasonic wind measuring instrument When ultrasound propagates in the air, it will superimpose with the airflow velocity in the wind direction. If the direction of ultrasound propagation is the same as the wind direction, its speed will increase; On the contrary, its speed will slow down, so the wind speed component can be used to measure the time difference between the transmissions of ultrasonic pulses in two opposite directions on a fixed path. The article adopts ultrasonic wind speed and direction measurement based on direct time difference method, which has the advantages of wind speed measurement being independent of temperature and not requiring temperature compensation. It is currently a widely used method for ultrasonic wind speed measurement.

As shown in Figure 1, assuming the distance between two ultrasonic heads is d, the propagation speed of ultrasonic waves in windless conditions is c, the wind speed is υ, and the transmission time of ultrasonic waves in downwind and headwind conditions is t12 and t21, respectively, then

From equations (1) and (2):

Equation (3) can be used to measure the wind speed component along the direction of the ultrasonic transducer. In order to measure the horizontal wind speed, two sets of orthogonal probes must be used to measure the two corresponding components, and the horizontal wind speed can be obtained by synthesizing them.

Users can choose wind speed units, output frequencies, and output formats according to their needs. Heating devices (recommended for use in cold environments) or analog outputs can also be selected as needed. It can be used in conjunction with computers, data collectors, or other acquisition devices that have RS485 or analog output compatibility. If necessary, multiple units can also form a network for use.

Example of ultrasonic pulse transmission circuit:

Key features of intelligent ultrasonic wind measurement instrument 

Wind speed measurement range: 0 m/s~75m/s

Maximum allowable error of wind speed ± 0.1m/s (<5m/s) ± 2% (>5m/s)

Wind speed resolution of 0.01 meters per second

Response time: 250 milliseconds

Start threshold: 0.01 meters per second

Wind direction measurement range 0~360 °

The maximum allowable error of wind direction is ± 2 °

Wind direction resolution of 0.1 °

Response time: 250 milliseconds

Start threshold: 0.01 meters per second

Application fields of ultrasonic wind measurement instrument Used for meteorological and environmental monitoring, real-time collection of wind speed and direction data is carried out on meteorological stations, high-altitude detection balloons, and mobile observation vehicles, providing key information for meteorological analysis. At the same time, it will assist in the analysis of wind fields in the study of haze diffusion models and urban heat island effects, in order to gain a deeper understanding of environmental meteorological changes. Monitoring in the aerospace field involves monitoring wind shear and turbulence around airport runways and terminals to ensure safe takeoff and landing of aircraft and reduce flight risks. Energy industry monitoring, in wind power plants, improves power generation efficiency and energy output by accurately measuring wind speed and direction, optimizing wind turbine layout. Industrial safety monitoring, chemical plants and refineries use ultrasonic wind measuring instruments to simulate gas leakage and diffusion situations, issue safety warnings in advance, and ensure industrial production safety. Agricultural and ecological protection monitoring plays a role in the design of windbreak forests and greenhouse ventilation control in farmland, promoting the optimization of agricultural production environment; In the forest fire warning system, it is used for predicting the spread of fire and enhancing forest fire prevention capabilities. Monitoring of transportation infrastructure, conducting wind vibration monitoring on cross sea bridges and high-speed railways, evaluating structural safety, and ensuring stable operation of transportation facilities; Provide real-time wind speed guidance for ship berthing at the port to ensure the safety of ship berthing. Offshore operation monitoring, with its anti-salt&spray corrosion characteristics, is applied to the safety monitoring of oil drilling platforms, adapting to complex and harsh offshore environments.

Summary: The ultrasonic wind measurement instrument is based on the direct time difference method, which calculates the wind speed component by detecting the time difference of ultrasonic waves in the downwind/upwind path. It has the advantages of no mechanical wear, high accuracy (± 0.1m/s), and full range response (0-75m/s). The system uses a 40kHz/200kHz transducer, combined with a pulse transformer boost and peak detection circuit, to reduce hardware costs while ensuring accuracy. The key parameters include: wind speed resolution of 0.01m/s, wind direction error of ± 2 °, and response time of 250ms. Widely used in meteorological monitoring, wind power optimization, industrial safety, transportation infrastructure, and offshore operations, especially suitable for long-term reliable measurement in harsh environments.