An anemometer is an instrument that measures the air flow rate. It has many types. The most commonly used meteorological station is the wind cup anemometer. It consists of three parabolic cones that are fixed to each other at 120°. The concave surface of the empty cup is in one direction. The entire sensing portion is mounted on a vertical rotating shaft, and the wind cup rotates around the shaft at a speed proportional to the wind speed under the action of the wind.
Anemometer selection requirements
The basic principle of an anemometer is to place a thin wire in a fluid, and the current is heated to make the temperature higher than the temperature of the fluid. Therefore, the wire anemometer is called a "hot wire". When the fluid flows through the wire in a vertical direction, a portion of the heat of the wire is removed, causing the temperature of the wire to drop. According to the forced convection heat exchange theory, it is possible to derive a relationship between the heat loss Q of the heat ray and the velocity v of the fluid. The standard hot wire probe consists of two short and thin wires tensioned by two brackets. The wire is usually made of a metal having a high melting point and good ductility such as platinum, rhodium or tungsten. The usual wire diameter is 5μm and the length is 2 mm; the smallest probe diameter is only 1μm and the length is 0.2 mm. According to different purposes, the hot wire probe is also made into double wire, three wire, oblique wire and V shape, X shape and the like. 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 thermal film probe. The hot wire probe must be calibrated before use. Static calibration is performed in a dedicated standard wind tunnel to measure the relationship between flow rate and output voltage and to draw a standard curve; dynamic calibration is performed in a known pulsating flow field or in an anemometer heating circuit The last pulse electric signal is used to verify the frequency response of the hot wire anemometer. If the frequency response is not good, the corresponding compensation line can be used to improve.
The flow rate measurement range of 0 to 100 m/s can be divided into three sections: low speed: 0 to 5 m/s; medium speed: 5 to 40 m/s; high speed: 40 to 100 m/s. The anemometer's thermal probes are used for accurate measurements from 0 to 5 m/s; the anemometer's rotary probes are ideal for measuring flow rates from 5 to 40 m/s; and the pitot tube is best for high speeds. result. An additional standard for the correct selection of an anemometer's flow rate probe is temperature. Typically, an anemometer's thermal sensor uses a temperature of approximately +-70C. The special anemometer's rotor probe can reach 350C. Pitot tube is used for +350C or above.
Anemometer maintenance
The wind speed meter belongs to the meter for safety protection and environmental monitoring, and is a mandatory verification measuring instrument prescribed by China's measurement law. In addition to the factory sales need to have the corresponding calibration report, it is also required to go to the National Air Conditioning Equipment Quality Supervision and Inspection Center or the China Academy of Building Research to build energy and energy every year according to the requirements of JJG (Construction) 0001-1992 "Hot Ball Anemometer Calibration Regulations". The environmental testing center performs regular calibration and adjusts all aspects of the instrument according to its legal calibration certificate to obtain the best working condition.
In addition to maintaining the accuracy of daily data, the following points should be noted in routine maintenance:
1. It is forbidden to use an anemometer in a flammable gas environment.
2. It is forbidden to place the anemometer probe in a flammable gas. Failure to do so may result in fire or even explosion.
3. Please use the anemometer correctly according to the requirements of the instruction manual. Improper use can result in electric shock, fire, and damage to the sensor.
4. In use, if the anemometer emits an unusual smell, sound or smoke, or if liquid flows into the anemometer, shut down the battery immediately. Otherwise, there is a danger of electric shock, fire and damage to the anemometer.
5. Do not expose the probe and anemometer body to rain. Otherwise, there may be electric shock, fire and personal injury.
6. Do not touch the internal sensor part of the probe.
7. When the anemometer is not used for a long time, remove the internal battery. Otherwise, the battery may leak and the anemometer may be damaged.
8. Do not place the anemometer in a place subject to high temperatures, high humidity, excessive dust and direct sunlight. Failure to do so may result in damage to internal components or deterioration of anemometer performance.
9. Do not wipe the anemometer with volatile liquids. Otherwise, it may cause deformation and discoloration of the anemometer housing. When there is stain on the surface of the anemometer, use a soft fabric and a neutral detergent to wipe.
10. Do not drop or press the anemometer. Failure to do so will result in malfunction or damage to the anemometer.
11. Do not touch the sensor's sensor area while the anemometer is energized. Otherwise, it will affect the measurement results or cause damage to the internal circuit of the anemometer.
Features
1. High sensitivity and accurate measurement
2, simple design
3, the wind speed measuring handle can be separated from the fuselage for easy measurement
4, dual display reading LCD
5, the wind speed measurement with 2 meters of extendable spiral
6, low power consumption
7, data retention, maximum and minimum hold function
8, low battery indication
9, bearing: sapphire bearing
10, temperature sensor: K-type thermocouple
Instructions
1. Before using, observe whether the pointer of the meter points to zero. If there is any offset, gently adjust the mechanical adjustment screw of the meter to return the pointer to zero point. 2. Place the calibration switch in the off position.
3. Insert the measuring rod plug into the socket, the measuring rod is placed vertically upwards, the screw plug is pressed tight to seal the probe, the "correction switch" is placed at the full position, and the "full adjustment" knob is slowly adjusted to make the meter pointer In fullness position;
4. Set the "correction switch" to "zero position", and slowly adjust the "coarse adjustment" and "fine adjustment" two knobs so that the meter pointer points to the zero position.
5. After the above steps, gently pull the screw plug to expose the probe (the length can be selected as needed), and make the red dot on the probe face the wind direction. According to the meter reading, check the calibration curve. Detecting the measured wind speed;
6. After measuring a few points (about 10min), the above steps 3 and 4 must be repeated to standardize the current in the meter.
7. After the test, the "correction switch" should be placed in the off position.
An anemometer that converts a flow rate signal into an electrical signal that also measures fluid temperature or density. The principle is that a thin wire (heating wire) that is heated by electricity is placed in the airflow, and the heat dissipation amount of the hot wire in the airflow is related to the flow velocity, and the heat dissipation causes the temperature of the hot wire to change, causing the resistance change, and the flow rate signal is converted into electric signal. It has two working modes: 1 constant current. The current through the hot wire remains unchanged. When the temperature changes, the heat line resistance changes, so the voltage at both ends changes, thereby measuring the flow rate; 2 thermostatic type. The temperature of the hot wire remains the same, such as maintaining 150 ° C, the flow rate can be measured according to the current applied. The thermostatic type is more widely used than the constant current type. The length of the hot wire is generally in the range of 0.5 to 2 mm, and the diameter is in the range of 1 to 10 μm. The material is platinum, tungsten or platinum-iridium alloy. If a thin metal film (thickness less than 0.1 micron) is used instead of the metal wire, it is a hot film anemometer, which functions similarly to the hot wire, but is mostly used to measure the liquid flow rate. In addition to the ordinary single line type, the hot line can also be a combined two-wire or three-wire type to measure the velocity component in all directions. The electric signal output from the hot line is amplified, compensated and digitized and input into the computer, which can improve the measurement accuracy, automatically complete the data post-processing process, and expand the speed measurement function, such as simultaneously completing the instantaneous value and the time average value, the combined speed and the sub-speed, and the turbulence. And measurements of other turbulence parameters. Compared with pitot tube, hot wire anemometer has small probe volume and small interference to flow field; fast response, can measure unsteady flow rate; can measure very low speed (such as as low as 0.3 m / s).
application
Anemometers are widely used and can be used flexibly in all fields. They are widely used in electric power, steel, petrochemical, energy conservation and other industries. There are other applications in the Beijing Olympic Games, sailing competitions, rowing competitions, field shooting competitions, etc. Both need to use an anemometer to measure. The anemometer has been advanced, in addition to measuring the wind speed, it can also measure the wind temperature and air volume. There are many industries that need an anemometer, the recommended industry: the fishing industry, all kinds of fan manufacturing, industries that need exhaust ventilation systems, and so on.
The different seasons and different geographical situations of the anemometer will make the wind direction in the atmosphere constantly changing. If the wind direction is different day and night, there are different monsoons in winter and summer. Research winds can help us predict and study climate change. An anemometer is required to study the wind direction. The design of the anemometer is mostly arrow-shaped, and it is also made into an animal shape, like a cock. The part of the anemometer's arrow feathers will rotate with the wind. The anemometer needs to be installed in a place where there is no building or tree to block the movement of the wind. Use and scope of application QDP series hot ball electric anemometers are used in heating, ventilation, air conditioning, meteorology, agriculture, chilling and drying, labor hygiene surveys, etc., and can be used when measuring indoor and outdoor or model airflow speeds. It is a basic instrument for measuring low wind speed. The product was rated as a quality product in Beijing by the Beijing Economic Commission in 1987. Working principle The instrument consists of two parts: a hot ball sensor and a measuring instrument. The sensor has a tiny glass ball on its head. The ball is filled with a nickel-chromium wire coil that heats the glass and two series of thermocouples. The cold end of the thermocouple is connected to the phosphor bronze pillar and directly exposed to the gas flow. When a certain amount of current passes through the heating coil, the glass bulb is heated to a certain temperature, which is related to the velocity of the gas flow. High, otherwise the temperature is lower.
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