Briefly introduce the probe and use of anemometer

Briefly introduce the probe and use of anemometer

Anemometer definition: Anemometers are instruments that measure air flow rates and can automatically record wind speeds continuously.

Anemometer It is divided into two forms: impeller type and thermal type general selection mainly to look at its wind speed, (common measurement range 0-30m/s 0-45m/s 0-60m/s)

Anemometer thermal probe

The principle of the anemometer's thermal probe is based on the cold-impinging airflow that removes the heat from the thermal element. With a regulating switch that maintains a constant temperature, the adjustment of the current and the flow rate is proportional. When thermal probes are used in turbulent flow, the air flow from all directions strikes the heat element at the same time, which affects the accuracy of the measurement results. When measuring in turbulent flow, thermal anemometer flow sensor values ​​tend to be higher than those of swivel probes. The above phenomena can be observed during the pipeline measurement. Depending on the design of the turbulence in the management pipeline, it can even occur at low speeds. Therefore, the anemometer measurement process should be performed on the straight part of the pipeline. The starting point of the straight part should be at least 10 × D before the measuring point (D = pipe diameter in CM); the ending point is at least 4 × D after the measuring point. The fluid cross section must not have any blockage. (corners, resuspended, objects, etc.)

Anemometer Rotary Probe

The working principle of the anemometer's rotary probe is based on converting the rotation into an electrical signal, first passing through a proximity sensor head, “counting” the rotation of the rotating wheel and generating a series of pulses, and then processing by the detector. Get the speed value. The anemometer's large-diameter probe (60mm, 100mm) is suitable for measuring turbulence in medium and small flow rates (eg at the outlet of pipes). The anemometer's small-bore probe is more suitable for measuring air flow with more than 100 times the cross-section of the explorer head.

Anemometer main purpose

1. Measure the speed and direction of the average flow.

2. Measure the fluctuating speed and frequency spectrum of incoming flow.

3. Measure the Reynolds stress in the turbulent flow and the velocity correlation and time correlation between the two points.

4. Measure the wall shear stress (usually using a hot-film probe placed flush with the wall, the principle is similar to the hot-wire speed measurement).

5. Measure the temperature of the fluid (measure the change of the probe resistance with the temperature of the fluid in advance, and then determine the temperature based on the measured resistance of the probe.