Basic knowledge about digital anemometers
The wind speed (flow speed) test includes the test of the average wind speed and the test of the turbulent flow component (wind turbulence 1 to 150KHz, different from fluctuation). Thermal anemometers measure the average wind speed. There are thermal type, ultrasonic type, impeller type, and Pitot tube type to test the average wind speed, but among these methods, the permanent anemometer uses the principle of heat dissipation. Next, the measurement methods of these wind speeds will be described.
Thermal Anemometer
This method is to test the resistance change when the sensor is cooled by the wind when it is powered on, so as to test the wind speed. No information on wind direction can be derived. In addition to being easy to carry and convenient, the cost-performance ratio is high, and it is widely used as a standard product of anemometers.
The elements of thermal anemometers use platinum wires, thermocouples, and semiconductors, but our company uses platinum coiled wires. The material of the platinum wire is physically stable. Therefore, there are advantages in long-term stability as well as in temperature compensation.
Ultrasonic
This method is to test the time of ultrasonic transmission for a certain distance, and the arrival time is delayed due to the influence of the wind, thereby testing the wind speed.
3 power, you can know the wind direction.
The sensor part is large, and turbulent flow may occur around the test part, making the flow irregular. Use is restricted. Low popularity.
impeller
This method is to apply the principle of the windmill to test the wind speed by testing the number of revolutions of the impeller. For meteorological observation, etc. The principle is relatively simple and the price is cheap, but the test accuracy is low, so it is not suitable for the test of slight wind speed and small wind speed change.
Pitot tube
On the front of the flow surface, there are small holes forming a right angle to it, and thin tubes for extracting pressure from each hole are hidden inside. By testing the pressure difference (the former is full pressure and the latter is static pressure), the wind speed can be known.
The principle is relatively simple and the price is cheap, but it must be set at right angles to the flow surface, otherwise the correct test cannot be performed. Not suitable for general use.
It is used not as an anemometer, but as an wind speed correction in the high-speed range.
