A duct air flow measuring device is a tool used to measure the air flow in a duct system. It is used to determine the amount of air that is being moved through the ducts, as well as the velocity of the air. This is important for determining the efficiency of the system, as well as for troubleshooting any problems that may arise. The device works by measuring the pressure drop across the duct, which is then used to calculate the air flow rate. The device can also be used to measure the temperature of the air, which can be used to adjust the air flow rate if necessary. The device is typically installed in the ducts, and is connected to a controller that allows the user to adjust the settings. This device is an essential tool for anyone working with duct systems, as it allows them to accurately measure the air flow rate and make adjustments as needed.