This section provides an overview for hot wire anemometers as well as their applications and principles. Also, please take a look at the list of 10 hot wire anemometer manufacturers and their company rankings.
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The hot wire anemometer is an instrument that measures wind velocity by utilizing the principle that when wind is applied to the probe, the hot wire inside the probe is cooled by the wind. It is often used to evaluate the performance of air conditioning systems and ventilation ducts. Other types of anemometers include vane anemometers and pitot anemometers. Compared to other types of anemometers, the hot wire anemometer is suitable for indoor measurements where temperature changes are minimal. They also have the advantage of being able to make measurements even in small spaces.
As mentioned above, hot wire anemometers are used for indoor measurements. They are used for maintenance and management of air conditioning systems and for environmental evaluation in clean rooms. The probe equipped with a sensor is connected to the main unit by a cable, and the probe is placed directly near an air vent, such as the exhaust port of an air conditioning system, for measurement. Depending on the device, it can measure not only air velocity but also air volume and temperature in many cases. Except for cases used in clean rooms, dust and debris often adhere to the hot wire, affecting the measurement. Therefore, periodic maintenance and calibration are required.
Hot wire anemometers apply the heat loss of metal wire to determine wind velocity. A heated metal wire (e.g., platinum is used for the hot wire) is incorporated inside the probe. When the probe is exposed to wind, the temperature of the metal wire decreases. This is because the temperature of the metal wire is transferred to the surrounding air. The amount of heat transferred is called heat dissipation. A stronger the wind equates to a lower temperature of the metal wire. The wind speed is obtained from the relationship between the amount of wind and the amount of heat dissipated. This is based on an approximate formula using King's formula, which states that "the amount of heat lost is proportional to one-half the wind speed." The amount of heat lost is measured by the electrical resistance of the metal wire. Hot wire anemometers use changes in temperature to measure wind speed. Therefore, if the wind temperature changes, the wind speed cannot be calculated correctly. Therefore, to avoid the influence of the wind temperature changes, compensation by wind temperature is performed. This function is called the temperature compensation function. Anemometers with a temperature compensation function are also available.
Hot wire anemometers are compact and can easily measure wind speed. However, they are not suitable for measuring air containing flammable gases because they measure air velocity by heating a metal wire. Care must be taken because of the risk of explosion.
*Including some distributors, etc.
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