The vane anemometer is an instrument used to measure the speed of air flow. The vane anemometer is generally composed of a vane and a counting mechanism. The measuring range of the vane anemometer is 0.5 to 10 m/s.
Working Principle
The vane anemometer is composed of vane and computing mechanism, as shown in the figure. The vanes are made of several light aluminum vanes. When measuring, the rotating surface of the vanes is perpendicular to the airflow direction, and the rotation direction should be paid attention to. The number of revolutions of the vanes is connected to the counting mechanism through mechanical transmission. The counting mechanism counts through the pointer in the middle of the dial, and the long pointer is 100m per revolution. The short pointer is below the dial, turning one scale is 100m, and one circle is 1000m.
Cassification
Vane anemometers can be divided into two types according to their calculation mechanism:
One is the built-in timing device, which can directly read the wind speed (m/min), which is called a self-recording vane anemometer. This instrument has a red chronograph hand on the left side of the dial, and a circle is 120 seconds (the first 30 seconds and the last 30 seconds are the preparation and finishing time respectively, and the actual counting time is only 60 seconds). Therefore, the reading at this time is the wind speed per minute. Some have been converted in the counting mechanism, so that the resulting wind speed is the wind speed per second.
The other is without a timing device, and a stopwatch must be prepared when using it, which is called a non-self-recording vane anemometer.
Precautions When Uusing Vane Anemometer
Due to the inertia and mechanical friction of the instrument itself, the pointer reading of the anemometer may not reflect the real air velocity. Therefore, after the air velocity is obtained from the formula v=(b-a)/t : (v is the measured wind speed m/s; b is the reading after measurement; a is the original reading; t is the measurement time), it must be corrected according to the calibration curve of the anemometer.
Before the vane anemometer is used, it must be calibrated with a wind cylinder or mutually calibrated with the calibrated vane anemometer.