Anemometer Probe Selection and Features
Thermal probes for anemometers
The working principle of the thermal probe of the anemometer is based on the cold impact air flow 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, the indication value of the thermal anemometer flow sensor is often higher than that of the rotary probe. The above phenomenon can be observed in the pipeline measurement process. Depending on the design of the managed pipe turbulence, it can occur even at low speeds. Therefore, the anemometer measurement process should be carried out on the straight part of the pipeline. 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. (angular, resuspended, objects, etc.)
Rotary Probe for Anemometers
The working principle of the rotating wheel probe of the anemometer is based on converting the rotation into an electrical signal. First, it passes through a proximity sensor to "count" the rotation of the rotating wheel and generate a pulse series, which is then converted by the detector. Get the 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-caliber probe of the anemometer is more suitable for measuring the airflow where the cross-section of the pipe is more than 100 times larger than that of the exploration head.
features
1. Small size, little interference to the flow field;
2. Wide range of applications. It can be used not only for gas but also for liquid, and can be used in subsonic, transonic and supersonic flows of gases
3. High frequency response up to 1 MHz.
4. High measurement accuracy and good repeatability. The disadvantage of the hot wire anemometer is that the probe interferes with the flow field, and the hot wire is easy to break.
5. In addition to measuring the average velocity, it can also measure the pulsation value and turbulence; in addition to measuring the single-directional movement, it can also measure the velocity components in multiple directions at the same time.
