The anemometer uses a volume flow funnel at the air extraction hole for measurement:
Even without the interference of grids at the exhaust point, the airflow path has no direction and its cross-section is extremely uneven. The reason is the local vacuum inside the pipeline, which extracts air in a funnel-shaped manner into the chamber. Even in areas very close to the extraction, there is no position that meets the measurement conditions for measurement operations. If the grid measurement method with average calculation function is used for measurement, and the volumetric flow rate method is used for measurement, only the pipeline or funnel measurement method can provide reproducible measurement results. In this case, measuring funnels of different sizes can meet the usage requirements. By using a measuring funnel, a fixed section that meets the flow velocity measurement conditions can be generated at a certain distance in front of the sheet valve. The center of the section can be measured and fixed, the center of the section can be measured and fixed, and the center of the section can be measured and fixed. The measured value obtained by the flow velocity probe is multiplied by the funnel coefficient to calculate the extracted volumetric flow rate. (such as funnel coefficient of 20)
Wheel type probe of anemometer
The working principle of the anemometer's rotary probe is based on converting rotation into electrical signals. First, it passes through a proximity sensing head to "count" the rotation of the rotor and generate a pulse series. Then, it is converted and processed by the detector to obtain the speed value. The large-diameter probe (60mm, 100mm) of the anemometer is suitable for measuring turbulent flow with medium to low velocities (such as at pipeline outlets). The small-diameter probe of the anemometer is more suitable for measuring airflow in pipelines with a cross-sectional area larger than that of the exploration head by more than 100 times. The correct adjustment position of the anemometer's rotary probe in the airflow is that the airflow direction is parallel to the rotary axis. When the probe is gently rotated in the airflow, the reading will change accordingly. When the reading reaches the maximum value, it indicates that the probe is in the correct measurement position. When measuring in a pipeline, the distance from the starting point of the straight part of the pipeline to the measurement point should be greater than 0XD. Turbulence has a relatively small impact on the thermal sensitive probe and pitot tube of the anemometer.
Practice has shown that the 16mm probe of an anemometer is the most widely used for measuring airflow velocity inside pipelines. Its size ensures good permeability and can withstand flow velocities up to 60m/s. The measurement of airflow velocity inside pipelines is one of the feasible measurement methods, and the indirect measurement protocol (grid measurement method) is applicable to air measurement.
