Hot wire anemometers are mainly used to measure air velocity or airflow speed. Hot wire anemometers are mainly used to measure the core parameter of wind speed, but the measurement process will also be affected by some environmental factors, and these environmental factors may have a certain interfere with the measurement results. The following are some environmental factors related to hot wire anemometer measurement.
Features of hot wire anemometer
Hot wire anemometer can meet various precision measurement needs, especially in fluid mechanics experiments, it can provide accurate flow velocity data. The probe of the hot wire anemometer is small in size and has less interference to the flow field, which makes it advantageous in some measurement occasions with high requirements for flow field interference. Compared with laser velocimetry, a hot wire anemometer has the advantage of a continuous signal. It does not require adding particles to the flow field, nor is it limited by the transparency of the flow field, making it more widely used.
Environmental influence on hot wire anemometer measurement
The influence of the environment on hot wire thermo anemometers is multifaceted, and these factors may cause measurement errors, thereby affecting the accuracy and reliability of hot wire anemometers. To obtain accurate measurement results, many environmental factors should be considered when using hot wire anemometers, and corresponding measures should be taken to reduce their impact on the measurement results.
Wind speed
This is the main parameter measured by electric anemometers and indicates the speed of airflow.
Air temperature
Hotwire anemometers rely on the principle of heat transfer. The wire is heated, and when air flows through it, the cooling rate depends on the airflow speed and air temperature. The relationship between wire heating and airflow speed is affected by air temperature. Therefore, temperature changes will affect the readings, which is why some anemometers also have temperature compensation functions or use separate temperature sensors.
Humidity (indirectly)
Humidity affects the thermal conductivity of the air, which in turn affects how quickly the wire cools. Higher humidity causes the air to conduct heat differently, changing the measurement. While hot wire anemometers do not measure humidity directly, high humidity can cause small errors or changes in velocity readings, especially if the calibration does not account for this.
Air density
Air density is affected by temperature, humidity, and pressure. As air density changes, the heat transfer properties of the hot wire affect the reading. In specific settings, air density may need to be considered (especially when measuring in extreme conditions), although anemometers do not typically measure air density directly.
Pressure (indirect)
Atmospheric pressure can also indirectly affect measurements, as changes in pressure affect air density. However, most thermal anemometers are designed to operate under standard atmospheric conditions, and significant pressure changes, such as those found at higher altitudes, may require a compensating factor.
Airflow direction
Hot-wire anemometers are generally more sensitive to wind speed in a particular direction. If the airflow direction does not coincide with the sensitive axis of the hot-wire sensor, measurement errors may result. Therefore, when using, ensure that the hot-wire anemometer is properly aligned with the airflow direction.
Contamination and particulate matter
Contaminants such as dust and oil mist in the air may adhere to the hot-wire sensor, affecting its heat dissipation performance, resulting in measurement errors. Therefore, regular cleaning of the hot-wire sensor is necessary.
Electromagnetic interference
Electromagnetic fields may interfere with the signal transmission and processing of the hot-wire anemometer, especially when used in a strong electromagnetic environment (such as near high-voltage power lines).
Vibration and mechanical interference
Mechanical vibration may affect the stability and measurement accuracy of the hot-wire sensor. Therefore, when using a hot-wire anemometer, try to avoid exposing it to vibration sources.
