1. Probe selection for anemometer

In the measurement range of flow velocity from {{0}} to 100m/s, we can divide it into three sections: low velocity: 0 to 5m/s; medium velocity: 5 to 40m/s; high velocity: 40 to 100m/s. The thermal probe of the anemometer is used for the best measurement of 0 to 5m/s; the impeller probe of the anemometer is ideal for measuring the flow velocity of 5 to 40m/s; and the pitot tube can get the best results in the high speed range.

1. The thermal probe has excellent measurement effect, and the wind speed range is generally 0-30m/s.

2. The diameter of the impeller can be selected for the impeller probe, and impellers of different sizes have different applications. For example, if a large impeller with a diameter of 100mm is selected, the average wind speed of a circular area with a diameter of 100mm can be measured. In addition, the impeller probe can be attached with a cover to achieve the effect of accurately measuring the air volume of small air outlets.

3. Pitot tubes are generally used to measure the wind speed of pipelines, which are suitable for large wind speeds. Generally, Pitot tubes are not recommended for wind speeds less than 5m/s.

An additional criterion for the correct selection of the anemometer probe is temperature: usually the temperature of the thermal sensor of the anemometer is about -20~70˚C. Ordinary impeller probes are also around -20~70˚C, but impeller probes can be specially made to withstand high temperatures of 350˚C. Pitot tubes have the widest range of applications for temperature, even the most common probes can withstand high temperatures of 600˚C.

2. Working principle of different anemometers

1. Thermal probe of anemometer

When measuring in turbulent flow, the indication value of the thermal anemometer flow sensor is often higher than that of the impeller 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.)

2. The impeller probe of the anemometer

The working principle of the impeller 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 impeller and generate 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-caliber probe of the anemometer is more suitable for measuring the air flow where the cross-section of the pipe is more than 100 times larger than the cross-sectional area of the exploration head.

3. Pitot tube probe of anemometer

The dynamic pressure characteristics of the fluid can be measured by using the Pitot tube, and the velocity of the fluid can be calculated according to the following formula. 1) where Pd——dynamic pressure of the fluid, Pa;

r—fluid weight, N/m3;

g—gravitational acceleration, m/s2.