How to choose the right air volume meter and anemometer?
The measurement range of flow velocity from 0 to 100m/s can be divided into three sections: low speed: 0 to 5m/s; Medium speed: 5 to 40m/s; High speed: 40 to 100m/s. The thermal sensitive probe of the anemometer is used for accurate measurement from 0 to 5m/s; The rotary probe of the anemometer has an ideal effect on measuring flow velocities ranging from 5 to 40m/s; The application of pitot tubes can achieve excellent results within the high-speed range. An additional criterion for correctly selecting the flow velocity probe of an anemometer is temperature, and the operating temperature of the thermal sensor of an anemometer is usually around+-7 ° C. The rotary probe of the specially designed anemometer can reach 35 ° C. Pitot tubes are used for temperatures above+35 ° C.
The working principle of the thermal sensitive probe of the anemometer
It is based on the cold shock airflow taking away the heat from the heating element, and with the help of a regulating switch, maintaining a constant temperature, the regulating current is proportional to the flow rate. When using a thermal sensitive 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 thermal anemometer velocity sensor is often higher than that of the rotary probe. The above phenomenon can be observed during the pipeline measurement process. According to different designs for managing turbulent flow in pipelines, it may even present at low speeds. Therefore, the measurement process of the anemometer should stop locally in the straight line of the pipeline. The starting point of the local straight line should be at least 10 × D (D=pipe diameter, in CM) outside the measurement point; The endpoint should be at least 4 × D behind the measurement point. The fluid cross-section must not have any obstruction.
