Instructions on how to measure anemometer
Anemometers measure wind, which is the horizontal movement of air.
Meteorological wind observation includes two parts: wind direction observation and wind speed observation. The wind direction and the direction of horizontal airflow are commonly represented by 16 geographical directions in ground meteorological observations. Wind speed is the distance that air travels per unit time, in m/s.
In addition to instantaneous wind speed and wind direction, wind measurement mainly uses the arithmetic mean method or vector mean method to calculate the average wind speed and wind direction, or uses the maximum wind direction to replace the average wind direction. The average wind generally refers to the time average of the instantaneous wind, and the difference between the instantaneous wind and the average wind is the pulsating wind.
Wind direction measurement uses a wind vane, and self-recording methods such as mechanical transmission, electrical transmission, and photoelectric conversion are used to record wind direction changes in real time.
Wind speed is measured with an anemometer (or anemometer). Commonly used anemometers (anemometers) include the following:
(1) Rotary anemometer (anemometer);
(2) Pressure anemometer: Use the pressure effect of the wind (wind pressure is proportional to the square of the wind speed) to measure wind speed;
(3) Thermal anemometer: Use the characteristics related to the heat dissipation rate of the heated object and the surrounding air flow speed to measure the wind speed;
(4) Acoustic anemometer: Use the functional relationship between the propagation speed of sound waves in the atmosphere and wind speed to measure wind speed.
The error in wind speed measurement is large, which is mainly caused by the hysteresis effect of the anemometer (anemometer).
Differences Between Anemometers
According to the principle, there are three main types of on-site anemometer measurement: differential pressure type, impeller type, and hot ball type.
The differential pressure method is a classic method of measuring flow velocity in fluid mechanics. It mainly relies on a pitot tube and a differential pressure meter to measure the dynamic pressure, and then calculates the flow velocity based on the Bernoulli equation. The advantages of this method are low detection limit and high sensitivity, but it requires high flow field uniformity. When measuring in the environment, it is easy to be inaccurate due to uneven flow field. Therefore, the pressure difference method is mainly used to measure wind speed in air ducts. .
The main principle of the hot ball type is that the probe sets a constant temperature. The air flows through the probe and takes away the heat. At this time, the probe will be heated to the set temperature. During this process, electrical signals will be collected by the instrument, and accordingly Convert to wind speed. The advantages of this method are high sensitivity, large range, and adaptability to environmental measurements. The disadvantage is that the platinum wire connecting the hot ball in the probe is relatively fragile. If you are not careful during use, the probe may be damaged and cannot be repaired. At present, the domestic hot ball anemometer is still an old-fashioned anemometer. The Air Conditioning Institute of the Institute of Construction Research has developed a more advanced alternative technology. The hot ball is replaced by a ceramic hot column, which is much stronger than the hot ball.
The impeller type mainly relies on the wind to rotate the impeller and produce electromagnetic signals for measurement. The advantage of this method is that the instrument is relatively durable and is often used for long-term measurements. The three-cup anemometer used in meteorological observations also uses the same principle. The disadvantage is that the sensitivity is slightly Difference.
