Which tool is typically used to measure the airflow rate in ducts?

The anemometer is the tool specifically designed for measuring airflow rate in ducts. It functions by calculating the velocity of air flowing through a given area, allowing technicians to determine how much air is being moved within the duct system. Anemometers can come in different types, such as handheld or stationary, and can measure various parameters, including velocity and volume flow rate, making them essential for ensuring that HVAC systems are operating efficiently.

Other options, while useful in their respective applications, do not have the capability to measure airflow directly. A pressure gauge is used to measure pressure differentials within a system, which is important for diagnosing issues but does not provide direct airflow measurements. A thermometer measures temperature, which, while relevant for HVAC systems, does not relate to airflow quantification. A caliper measures dimensions or thickness of materials and is not suited for airflow measurement. Thus, the anemometer stands out as the appropriate tool for assessing airflow in ducts.