Wind speed measuring instrument, the principle of classification and USES
anemometer its basic principle is a thin metal wire in a fluid, the flow of electricity heating wire, make its temperature is higher than the temperature of the fluid, so called wire anemometer hotline. When the fluid flows through the wire along the vertical direction, will take away part of the metal wire heat, temperature drops make wire. Been derived according to the theory of forced convection heat transfer, the hotline dissipating heat Q and the relation between velocity v of the fluid. Two supporting tension standard hotline probe by a short, thin wire, as shown in figure 2. 1. Wire normally with platinum, rhodium, high melting point, good ductility, such as tungsten metal. The commonly used wire diameter of 5 & mu; M, to 2 mm long; The smallest probe diameter only 1 & mu; M, length is zero. 2毫米。 According to different purposes, hotline probe is made double wire, three wire, wire and V, X, etc. In order to increase the strength, sometimes with a metal film instead of metal wire, usually on a thermal insulating substrate coating a layer of thin metal film, called the hot film probe, as shown in figure 2. 2. Hotline sensor must be calibrated before use. Static calibration was conducted in the specialized standard wind tunnel, measuring the velocity and the relationship between the output voltage and drawing standard curve; Dynamic calibration is done in pulsating flow field known, or in the anemometer heated circuit and a pulse signal, check the frequency response of hot wire anemometer, if poor frequency response available corresponding compensation circuit to improve them.
0 to 100 m/s of velocity measurement range can be divided into three sections: low speed: 0 to 5 m/s; Medium: 5 to 40 m/s; High speed: 40 to 100 m/s. Anemometer thermal probe is used for accurate measurement of 0 to 5 m/s; Anemometer turn wheel probe measurement 5 to 40 m/s the velocity effect of the ideal; While using pitot tube can be within the scope of the high speed to get the best results. Correct selection of the flow rate of the anemometer is an additional standard temperature of the probe, the use of thermal sensors usually anemometer temperature of about + - 70C。 Special anemometer wheel probe of up to 350 c. Pitot tube is used for more than + 350 c.
wind speed instrument belongs to safety, environmental monitoring kind measuring instrument, measurement in our country is the mandatory verification of measuring instruments. In addition to the factory sales need to be equipped with the appropriate calibration report, also need to according to JJG ( Construction) 0001 - 1992 'hot bulb anemometer verification regulation requirements regularly every year to the national air conditioning construction quality supervision and inspection center or the China construction science research institute in energy and environmental testing center regular calibration, and according to its legal calibration certificate issued by the instrument to adjust all aspects in order to obtain the best working state.
in addition to maintain the accuracy of the daily data, maintenance in use also note the following:
1. Prohibit use anemometer in the flammable gas environment.
2。 It is forbidden to anemometer probe in the combustible gas. Otherwise, it may cause fire or explosion.
3。 According to the requirements of the specification, please correct use of anemometer. Use undeserved, may cause damage to get an electric shock, fire and sensors.
4。 In use, in case of anemometer sends out a abnormal smell, sound, or smoke, or a liquid into the anemometer internal, please remove battery to turn it off immediately. Otherwise, there will be damaged by electric shock, fire, and the risk of anemometer.
5。 Don't expose probe and anemometer ontology in the rain. Otherwise, it may have the risk of electric shock, fire and injury and personal.
6。 Don't touch the probe sensor parts.
7。 Anemometer when not in use for a long time, remove the internal battery. Otherwise, the battery leakage, may cause damage of anemometer.
8。 Do not place anemometer at high temperature, high humidity, dusty and direct sunlight. Otherwise, will cause the damage of the internal components or anemometer performance deteriorate.