The working principle of different anemometers
1. Thermal probe of anemometer
The thermal probe is based on the cold impact airflow to remove heat from the thermal element. With the help of a regulating switch, the temperature is kept constant, and the regulating current is proportional to the flow rate. When using a thermosensitive probe in turbulence, airflow from all directions simultaneously impacts the thermal element, which can affect the accuracy of the measurement results.
When measuring in turbulence, the reading of the flow velocity sensor of the thermal anemometer is often higher than that of the blade probe. The above phenomena can be observed during pipeline measurement. According to different designs for managing pipeline turbulence, it can even occur at low speeds. Therefore, the anemometer measurement process should be carried out on the straight section of the pipeline. The starting point of the straight section should be at least 10 times before the measurement point × D (D=pipeline diameter, in CM); The endpoint should be at least 4 after the measurement point × Location D. The fluid cross-section must not have any obstruction. (edges, overhangs, objects, etc.)
2. Vane type probe of anemometer
The working principle of the impeller type probe of the anemometer is based on converting rotation into electrical signals. First, it passes through a proximity sensing start to "count" the rotation of the impeller and generate a pulse series. Then, it is converted and processed by the detector to obtain the speed value. The large-diameter probe of the anemometer (60mm, 100mm) is suitable for measuring turbulence at medium and small flow rates (such as at pipeline outlets). The small caliber probe of the anemometer is more suitable for measuring airflow with a cross-sectional area greater than 100 times that of the exploration head.
3. Pitot tube probe of anemometer
The dynamic pressure characteristics of a fluid can be measured using a pitot tube, and the velocity of the fluid can be calculated using the following formula. 1) In the formula, Pd - dynamic pressure of the fluid, Pa;
W - fluid velocity, m/s;
R - Fluid density, N/m3;
G - Gravitational acceleration, m/s2.
This is the principle of measuring wind speed with a Pitot tube.
