Solutions for Wind Speed Measurement Using Anemometers
Three types of anemometer probes are available: thermal probes, impeller probes, and pitot tubes.
Wind speed is divided into three measurement ranges:Low wind speed: 0 to 5 m/sMedium wind speed: 5 to 40 m/sHigh wind speed: 40 to 100 m/s
Pitot Tube
Pitot tubes are mainly used for high‑temperature measurement.The opening of the pitot tube receives total pressure and transmits it to pressure connection (a) of the probe. Pure static pressure enters through side slots and is guided to pressure connection (b). The resulting differential pressure is analyzed and converted to indicate wind pressure, which corresponds to dynamic flow pressure. Compared with impeller probes, pitot tubes respond better to turbulent flow than thermal probes. Therefore, unobstructed inlet and outlet paths must be ensured during pitot tube measurement.
Pressure Deviation
Since the calculation adopts a standard average air density of 1200 g/m³, measurement errors often occur. When measuring outdoor airflow, the actual air density may deviate by up to ±10 % from the reference value, resulting in airflow inaccuracy of approximately ±5 %. The testo 400 instrument compensates for this deviation through automatic pressure‑to‑wind‑speed conversion for pitot tubes. Multi‑point averaging can then be performed directly on the measured m/s values.
Thermal Anemometer Probe
Thermal anemometers are best suited for low wind speed measurement.The measuring principle of thermal probes is based on wind cooling effects. A sensing element is heated to a constant temperature and exposed to airflow. Wind speed is determined by measuring the energy required to maintain the preset temperature. The higher the wind speed, the more energy is needed to keep the temperature stable. Thermal anemometers adopt either hot‑wire or hot‑ball probe structures.
In practical applications, thermal probes excel at low velocity, vane probes suit the medium speed range, and pitot tubes deliver the highest accuracy at high wind speeds. Ambient operating temperature is another key factor for probe selection; thermal anemometers have a limited
temperature tolerance range.
Hot‑wire sensors feature high sensitivity with low power consumption but are fragile. By contrast, robust hot‑ball probes offer better durability yet require higher power to maintain temperature, shortening battery life. This distinction is noticeable during duct testing. Depending on duct structure, turbulence may occur even at low velocities. For reliable results, all measurements should be taken on straight duct sections.
