How does an anemometer operate?
Operating Principle of Anemometer The basic principle of anemometer is to place a thin metal wire in the fluid and pass current to heat the wire;
The temperature is higher than the temperature of the fluid, hence the wire anemometer is called a "wire".
When the fluid flows through the wire in a straight direction, it will take away part of the heat from the wire, causing the temperature of the wire to drop.
According to the forced convection heat exchange theory, it can be derived that there is a relationship between the heat Q lost from the dedicated line and the velocity v of the fluid. The standard dedicated line probe consists of two brackets tensioning a short and thin metal wire.
Metal wires are generally made of metals with high melting points and good ductility such as platinum, rhodium, and tungsten. Commonly used wires have 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 uses.
Special line probes are also made into double wire, triple wire, oblique wire, V-shape, X-shape, etc. In order to increase strength, metal films are sometimes used instead of metal wires. A thin metal film is usually sprayed on a thermally insulating substrate, which is called a hot film probe.
Special line probes must be calibrated before use. Static calibration is performed in a dedicated regulated wind tunnel.
The relationship between flow rate and output voltage is measured and drawn into a standard curve; dynamic calibration is performed in a known pulsating flow field;
Or add a pulsating electrical signal to the anemometer heating circuit to verify the frequency response of the dedicated line anemometer. If the frequency response is not good, it can be improved with the corresponding compensation circuit.
