Basic knowledge of the digital anemometer
The wind speed (flow speed) test includes the test of average wind speed and the test of turbulence component (wind turbulence 1 to 150KHz, different from fluctuation). Thermal anemometer measures average wind speed. Methods for testing average wind speed include thermal, ultrasonic, impeller, and drag tube methods, but among these methods, the anemometer uses the principle of heat dissipation. Next, the methods for measuring these wind speeds will be explained.
thermal anemometer
This method is to test the resistance change produced when the sensor is cooled by the wind when it is powered on, thereby testing the wind speed. No information about wind direction can be obtained. In addition to being easy to carry and convenient, it has a high cost-performance ratio and is widely used as a standard product of anemometers.
Thermal anemometers use platinum wire, thermocouples, or semiconductor elements, but our company uses platinum coiled wire. The material of platinum wire is the most stable materially. Therefore, it has advantages in terms of long-term stability and temperature compensation.
Ultrasonic
This method is to test the time it takes to transmit ultrasonic waves over a certain distance. The arrival time is delayed due to the influence of wind, thereby testing the wind speed.
When raised to the 3rd power, you can know the direction of the wind.
The sensor part is large, and turbulence may occur around the test part, causing the flow to become irregular. Usage restricted. Low popularity.
Impeller type
This method applies the principle of a windmill and tests the wind speed by testing the number of rotations of the impeller. Used for meteorological observations, etc. The principle is relatively simple and the price is cheap, but the test accuracy is low, so it is not suitable for testing of light wind speed and small wind speed changes.
Leather tube type
There are small holes at right angles to the front side of the flow surface, and there are thin tubes inside that extract pressure from each hole. 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 correct testing cannot be performed. Not suitable for general use.
It is not used as an anemometer but for wind speed correction in the high-speed range.
