Thermal probes for anemometers
The working principle of the thermal probe of the anemometer is based on the cold impact airflow taking away the heat on the heating element. With the help of an adjustment switch to keep the temperature constant, the adjustment current is proportional to the flow rate. When using thermal probes in turbulent flow, airflow from all directions impinges on the thermal element simultaneously, which can affect the accuracy of the measurement results. When measuring in turbulent flow, thermal anemometer flow sensors tend to give higher indications than rotary wheel probes. The above phenomenon can be observed in the pipeline measurement process. Depending on the design of the pipe turbulence can occur even at low speeds. Therefore, the anemometer measurement process should be
The straight section of the pipeline is carried out. The starting point of the straight line should be at least 10×D (D=pipe diameter, in CM) before the measuring point; the end point should be at least 4×D behind the measuring point. The flow section must not be obstructed in any way. (edges, heavy suspensions, etc.).
Rotary probe of the anemometer: The working principle of the rotary probe of the anemometer is based on converting the rotation into an electrical signal. First, it passes through a proximity sensor, "counts" the rotation of the rotor and generates a pulse series, and then converts it through the detector to obtain the rotational speed value. The large-diameter probe (60mm, 100mm) of the anemometer is suitable for measuring turbulent flow with medium and small flow rates (such as at the pipe outlet). The small-bore probe of the anemometer is more suitable for measuring the air flow whose cross-section of the pipe is more than 100 times larger than that of the probe.
The anemometer measures the relatively balanced distribution of the airflow in the pipe with a large vent in the extraction and exhaust: a high-speed area is generated on the surface of the free vent, and the rest is a low-speed area, and a vortex is generated on the grid. According to the different design methods of the grid, at a certain distance (about 20cm) in front of the grid, the airflow section is relatively stable. In this case, a large-diameter runner anemometer is usually used for measurement. This is because the larger bore is able to average the unbalanced flow rate and calculate its average value over a larger range.
