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How to choose the right anemometer and air volume meter?

日期:2020-09-28 16:53
浏览次数:107
摘要:The range of velocity measurement 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 thermosensitive probe of anemometer is used for accurate measurement from 0 to 5m/s; The rotating probe of anemometer measures the flow velocity from 5 to 40m/s with an ideal zui effect. However, the application of pitot tube can get better zui results in the high speed range. An additional criterion for the proper selection of speed
The range of velocity measurement 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 thermosensitive probe of anemometer is used for accurate measurement from 0 to 5m/s; The rotating probe of anemometer measures the flow velocity from 5 to 40m/s with an ideal zui effect. However, the application of pitot tube can get better zui results in the high speed range. An additional criterion for the proper selection of speed probes for anemometers is temperature. Normally, the temperature of the thermal sensors used for anemometers is up to +-7 red wine. The spinner of the specially designed speed tester can reach up to 35 speed. Pitot ots are used for +35 and up.



Working principle of thermosensitive probe of anemometer



Is based on the cold shock airflow away heat elements, with the aid of a conditioning switch, adhere to a constant temperature, conditioning current and flow rate is proportional to the relationship. When a thermosensitive probe is used in turbulence, airflow from all directions impinges on the thermal element simultaneously, thus affecting the accuracy of measurement results. When turbulence is measured, the velocity sensor of the thermosensitive anemometer is often higher than that of the rotary probe. The above phenomenon can be observed in the process of pipe measurement. Depending on the design of the pipeline to manage turbulence, it may also be present at low speeds. Therefore, the anemometer measurement process should be stopped locally in the straight line of the pipe. The local starting point of the straight line should be at least 10×D (D= pipe diameter, unit: CM) before the measurement point; The endpoint is at least 4×D after the measurement point. The fluid section shall not be screened. The working principle of the rotating probe of anemometer is based on the conversion of rotation into electrical signals, through an adjacent induction start, "count" the rotation of the rotating wheel and generate a pulse series, and then through the conversion and disposal of the detector, the rotational speed value can be obtained. The large diameter probe (60mm,100mm) of the anemometer is suitable for measuring turbulence at medium and small velocities. The small aperture probe of anemometer is more suitable for measuring airflow with a cross section more than 100 times the cross section area of exploration head. Positioning anemometer in air flow the correct position of the rotating wheel probe of anemometer is that the flow direction is parallel to the rotating wheel shaft. When the probe is quietly turned in the airflow, the indication will change accordingly. When the maximum reading is reached, the probe is indicated to be in the correct measurement position. When measuring in the pipeline, the interval between the starting point of the pipeline's flatness part and the measuring point should be large, so 0XD. Turbulence has relatively little influence on the thermosensitive probe and pitot tube of the anemometer. The theory of measuring the airflow velocity in the tube proves that the 16mm probe of anemometer is most useful. Its size not only ensures good permeability, but also can accept a higher flow rate of up to 60m/s. As one of the feasible measurement methods, the indirect measurement procedure (grid measurement method) is applicable to air measurement. VDI12080 provides the following procedures:



Square cross-section grid, common specifications of circular cross-section gate measurement, measurement specifications of circular cross-section gate centroid axis, measuring log linear specification anemometer in the measurement of suction and exhaust vent will greatly change the pipe flow distribution of the relative balance state: in free air breathers appearance produced high-speed, low speed region, other parts of and generate vortex on the grid. According to the different design methods of the grid, the airflow section is relatively stable at a certain interval (about 20cm) in front of the grid. In this case, the diameter of the large anemometer is usually used to stop the measurement. Because the larger diameter can stop the uneven flow velocity evenly, and calculate its uniform value in a larger range. The anemometer USES the volumetric flow funnel stop measurement in the suction hole: even if there is no grid interference at the extraction point, the air path has no direction, and its airflow section is extremely uneven. The reason is that the partial vacuum in the pipe is funneled out of the air in the air chamber. Even in the area where the air is pumped very close to each other, there is no place to stop the measurement. If the grid measurement method with the function of uniform value calculation is adopted to stop the measurement, and thereby affirm the volumetric flow method to stop the measurement, and thereby affirm the volumetric flow, etc., as long as the pipe or funnel measurement method can provide repeatable measurement results. In this case, measurement funnels of different sizes can meet the operational requirements. The measuring funnel can be used to generate a fixed section at a certain interval in front of the plate valve, which meets the requirement of velocity measurement, to locate and fix the center of the section, to locate and fix the center of the section, and to locate and fix the center of the section. The volume discharge can be calculated by multiplying the measured value obtained by the funnel coefficient. (e.g. funnel coefficient 20)