Introduction to related knowledge of anemometer
The basic principle of the anemometer is to place a thin metal wire in the fluid, and heat the wire through an electric current to make its temperature higher than the temperature of the fluid, so the wire anemometer is called "hot wire". When the fluid flows through the wire in the vertical direction, it will take away part of the heat of the wire and reduce the temperature of the wire. According to the theory of forced convection heat exchange, there is a relationship between the heat Q lost by the hot line and the velocity v of the fluid. A standard hot wire probe consists of a short, thin wire stretched between two brackets. Metal wire is usually made of platinum, rhodium, tungsten and other metals with high melting point and good ductility. The commonly used wire has a diameter of 5 μm and a length of 2 mm; the smallest probe has a diameter of only 1 μm and a length of 0.2 mm. According to different purposes, the hot wire probe is also made into double wire, triple wire, oblique wire, V shape, X shape, etc. In order to increase the strength, a metal film is sometimes used instead of a metal wire, and a thin metal film is usually sprayed on a thermally insulating substrate, which is called a hot film probe. Hot wire probes must be calibrated before use. Static calibration is carried out in a special standard wind tunnel, and the relationship between flow velocity and output voltage is measured and drawn as a standard curve; dynamic calibration is carried out in a known fluctuating flow field, or in the heating circuit of the anemometer. Check the frequency response of the hot-wire anemometer with the last pulsating electrical signal. If the frequency response is not good, it can be improved with the corresponding compensation circuit.
The measurement range of flow velocity from 0 to 100m/s can be divided 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 accurate measurement of 0 to 5m/s; the rotary probe of the anemometer is ideal for measuring the flow velocity of 5 to 40m/s; result. An additional criterion for the correct selection of the flow rate probe of the anemometer is the temperature. Usually, the temperature of the thermal sensor of the anemometer is about +-70C. The rotor probe of the special anemometer can reach 350C. Pitot tubes are used above +350C.
Anemometers are widely used and can be used flexibly in all fields. They are widely used in electric power, steel, petrochemical, energy-saving and other industries. In the Beijing Olympic Games There are other applications, such as sailing competitions, rowing competitions, field shooting competitions, etc., all need to use anemometers to measure. The anemometer is relatively advanced, in addition to measuring the wind speed, it can also measure the wind temperature and air volume. There are many industries that need to use anemometers, recommended industries: fishing industry, various fan manufacturing industries, industries that require ventilation and exhaust systems, etc.
Anemometer Different seasons and different geographical conditions will cause the wind direction in the atmosphere to change constantly. For example, the wind direction of the seaside is different day and night, and there are different monsoons in winter and summer. Studying wind direction can help us predict and study climate change. Studying wind direction requires the use of an anemometer. The design of the anemometer is mostly in the shape of an arrow, but also in the shape of an animal, like a rooster. The fletch part of the anemometer will rotate with the wind direction. The anemometer needs to be installed in a place where there are no buildings or trees that obstruct the movement of the wind. Purpose and scope of application QDP series thermal bulb electric anemometer is used in heating, ventilation, air conditioning, meteorology, agriculture, refrigeration and drying, labor hygiene investigation, etc. It can be used when it is necessary to measure the airflow velocity indoors and outdoors or models. It is a basic instrument for measuring low wind speed.
