One: The basic principle of thermal anemometer:
1. A thin wire is placed in the fluid, and the wire is heated by an electric current to make the temperature higher than the temperature of the fluid, so the wire anemometer is called. When the fluid flows through the wire in the vertical direction, it will take away part of the heat of the wire, causing the temperature of the wire to drop.
2. According to the theory of forced convection heat exchange, it can be derived that there is a relationship between the dissipated heat Q and the velocity v of the fluid. The standard probe consists of two brackets tensioned with a short, thin wire. Metal wires are usually made of metals with high melting points and good ductility such as platinum, rhodium, and tungsten.
3. According to different uses, the head is also made into double wire, three wire, oblique wire, V shape, X shape, etc. In order to increase the strength, sometimes a metal film is used to replace the metal wire, and a thin metal film is usually sprayed on a thermally insulating substrate, which is called a thermal film probe. Probes must be calibrated before use.
4. Static calibration is carried out in a special standard wind tunnel, measuring the relationship between flow rate and output voltage and drawing a standard curve; dynamic calibration is carried out in a known pulsating flow field, or in the anemometer heating circuit Add a pulsating electrical signal to the frequency response of the calibration line anemometer. If the frequency response is not good, the corresponding compensation circuit can be used to improve it.
Second: the use of thermal anemometer:
1. The anemometer is widely used and can be used flexibly in all fields. It is widely used in electric power, steel, petrochemical, energy saving and other industries. There are other applications in the Beijing Olympics, sailing competitions, rowing competitions, and field shooting competitions. All anemometers need to use anemometers to measure.
2. There are many industries that need to use anemometers. The recommended industries are: sea fishing, various fan manufacturing industries, industries that require exhaust systems, etc.
3. The working principle of the thermal probe of the anemometer is based on the cold impact airflow to take away the heat on the thermal element. With the help of an adjustment switch, to keep the temperature constant, the adjustment current is proportional to the flow rate.
4. When the thermal probe is used in turbulent flow, the airflow from all directions hits the thermal element at the same time, which will affect the accuracy of the measurement results. When measuring in turbulent flow, thermal anemometer flow sensors tend to have higher indications than rotor probes.
