Anemometers - Vane, Hot Wire

Anemometers – Vane, Hot Wire

Common instruments for measuring air velocity are anemometers – vane, hot wire. When velocity is measured in a duct, if the cross section of the duct is known, air volumetric flow can be readily computed. The common instruments used by the Safety, Industrial Hygiene and HVAC communities for air velocity measurements are vane anemometers, and at lower flow ranges hot wire anemometers. Pitot tubes with precision manometers are commonly used when it is necessary to measure high flow rates and also at high temperatures.

Vane anemometers in general are more rugged than hot wire instruments and have a much higher upper operating velocity than hot wire instruments. Vane diameters are available from about 1/2″ to 6″. With vane anemometers air velocity is proportional the the rotational speed of the vane, RPM, and accuracy drops off at low velocities. Accuracy is also dependent on the vane being positioned perpendicular to the air flow.

Hot wire anemometers are very accurate for measuring low air velocities, respond quickly to velocity changes, and are almost insensitive to air flow direction. Hot wire instruments are very handy for measurements in turbulent flow, such as after a change in flow direction at an elbow, valve or flow splitter.  Hot wire instruments are delicate and are easily damaged at high flow rates. Velocity or hot wire measurements are proportional to the ΔT between still air reference and the cooling of the heated wire from air moving past it. For hot wire anemometers accuracy falls off as the ambient (still air) temperature increases, decreasing the ΔT between the still air and flowing air.

The instruments sold by SMG have typical operating temperature ranges from about 0°C up to near 60°C. The temperature range being limited by the materials of construction, instrument design and desired accuracy. Products includes hot wire and vane anemometers,  many with datalogging (SD card memory). In addition many of the instruments incorporate other functions also as for example temperature, humidity, %RH and Indoor Air Quality monitoring.  If what you need is not under this classification we suggest looking in other classifications such as Indoor Air Quality or Heat Stress. And of course we are always available to take your questions via phone 972-985-0883, email or used the Contact Form.

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