Anemometer / Air Flow

Anemometer / Air Flow

Anemometers measure air movement. The term derives from the word anemos, which means wind, and refers to any air speed measurement instrument. These meters are often divided into categories: wind speed and air pressure. They measure various parameters such as air velocity, dew point, humidity, wind chill, and temperature.
 
There are a variety of types of anemometers, including sonic, vane (windmill), hotwire, cup, and laser. They are used in numerous applications such as HVAC, agriculture, athletics, construction, and more. These devices are accurate, portable, and durable.
 
Anemometer Applications

• Measure air velocity/air flow in HVAC ducts and other small openings
• HVAC installation, repair, diagnostics and optimization
• Promote good indoor air quality
• Maintain a comfortable environment
• Monitor indoor vs. outdoor pressure relationships and manage the building envelope

Types of Anemometers

• Sonic. These anemometers use ultrasonic sound waves
• Vane (Windmill). Vane anemometers combine a propeller and a tail on the same axis. Vane type anemometers have a vane similar to a propeller/impeller. The air flow thru the mechanical vanes or blades is translated into a velocity flow rate such as ft/min or meters/sec
• Hot-wire. These use electrically heated wires. The air cools the wire, and the device uses the temperature change to calculate the measurement
• Cup. The wind moves past the cups and turns the shaft. The air flow is measured by counting the number of turns of the shaft over a period of time
• Laser. These anemometers use a beam of light to measure the speed of particles

Vane and hot-wire types are the most popular. Here are pictures

Key Features of Anemometers to Consider

• Telescoping probe designed to fit into HVAC ducts and other small openings
• Datalogging and PC Communications
• Water resistant housing
• Multifunction capability: InfraRed Thermometer, temperarature probe, humidity, CO detection, light measurement, and/or more depending on model

Vane Type vs Hot-wire Anemometer

• Vane type are mechanical, more susceptible to long term wear & tear vs hot-wire which are more susceptible failure with sudden shocks or drops   
• Vane type have less accuracy drift over time   
• Hot-wire anemometers are more accurate, better resolution and faster response to rapid flow changes   
• Hot wire anemometers are easier to insert in ducts

This video discusses one type of vane anemometer that measures temperature, humidity, dew point, wet bulb, and even wind chill. It discusses some of the key features of an anemometer