Which device is commonly used to measure air velocity in HVAC ducts?

The device commonly used to measure air velocity in HVAC ducts is the anemometer. An anemometer specifically measures the speed and direction of airflow, making it an ideal tool for assessing air velocity in various applications, including HVAC systems.

In the context of HVAC, understanding airflow characteristics is crucial for ensuring efficient system performance, comfort levels, and energy efficiency. Anemometers can come in various forms, including handheld models and fixed installations, which allow technicians to pinpoint air velocity in different areas of a duct system.

Other devices mentioned, such as a barometer, measure atmospheric pressure; a thermocouple is designed to measure temperature; and an ultrasonic flowmeter is better suited for measuring fluid flow rates rather than air velocity. This highlights how anemometers are specifically tailored for the task, making them the correct choice in this context.