How to choose the right anemometer and anemometer?
Flow velocity measurements from 0 to 100 m/s can be divided into three zones: low speed: 0 to 5 m/s; medium speed: 5 to 40 m/s; and high speed: 40 to 100 m/s. Thermal anemometers are used to accurately measure flow velocities from 0 to 5 m/s; rotary anemometers are ideal for flow velocities from 5 to 40 m/s; and Pitot tubes are used to give good results in the high speed range. An additional criterion for the correct selection of an anemometer's flow velocity probe is the temperature, typically the thermal sensor of an anemometer can be operated at temperatures up to about +-7˚C, the rotating wheel probe of a special anemometer up to 35˚C, and the Pitot tube for use above +35˚C.
Principle of operation of anemometer thermal sensors
The principle of operation of the thermal probe is based on the fact that a cold impulse airflow carries away the heat from the thermal element, with the help of a regulating switch, which maintains the temperature at a constant level, then the regulating current is proportional to the flow rate. When the thermal probe is used in turbulent flow, the airflow from all directions impacts the thermal element at the same time, thus affecting the measurement results. Measured in turbulence, the thermal anemometer flow sensor is often higher than the rotating wheel type probe. The above phenomenon can be observed in the pipeline measurement process. Depending on the different designs for managing turbulence in ducts, even at low speeds. Therefore, the anemometer measurement process should be stopped in a straight line part of the pipe. The starting point of the straight line part should be at least 10×D (D=pipe diameter in CM) outside the front of the measurement point; the end point should be at least 4×D after the measurement point. The fluid cross-section shall not be obstructed in any way.
(corners, overhangs, objects, etc.) Rotary Probe for Anemometers
The working principle of anemometer's rotating wheel probe is based on the conversion of rotation into electrical signals, firstly through a proximity induction start, the rotation of the wheel to stop "counting" and produce a pulse series, and then converted and disposed of by the detector, you can get the value of the rotational speed. The large diameter probes (60mm, 100mm) of the anemometer are suitable for measuring turbulent flow in medium and small flow velocities. The small diameter probe of anemometer is more suitable for measuring the air flow with the cross-section of the pipe more than 100 times of the cross-sectional area of the probe.
Positioning of the anemometer in the air stream
The correct adjustment position of the anemometer's rotating probe is with the airflow direction parallel to the rotor axis. When the probe is quietly rotated in the air stream, the indicated value will change. When the reading reaches a large value, it is marked that the probe is in the correct measuring position. Measurement in the pipeline, the pipeline straight part of the starting point to the measurement point of the interval should be greater than 0XD, turbulence on the anemometer's thermal probe and Pitot tube of the relatively small impact.
Anemometer in the pipe airflow velocity measurement
The theory proves that the 16mm probe of anemometer is very useful. Its size ensures good permeability and accepts flow velocities of up to 60m/s. The 16mm probe has been shown to be very useful. The measurement of airflow velocity in ducts is one of the feasible measurement methods, and the indirect measurement protocol (grid measurement method) is applicable to air measurement.
