What device is used to measure static head, velocity head, and total head in a fan discharge duct?

The correct choice is the manometer, which is a device designed to measure pressure differences and can provide readings of static head, velocity head, and total head in a fluid system, such as a fan discharge duct.

In this context, the manometer uses a liquid column to indicate the pressure exerted by the fluid. By understanding the relationship between pressure and fluid velocity, the manometer can help quantify both static pressure (the pressure exerted by the fluid at rest) and dynamic pressure (related to the fluid's velocity, also known as velocity head). Combining these measurements allows one to determine the total head within the duct, crucial for diagnosing system performance and efficiency.

Other devices, such as an anemometer and a Pitot tube, have specific uses in fluid dynamics. An anemometer typically measures airflow velocity but may not directly measure static or total head. A Pitot tube is specifically designed to measure dynamic pressure and is often combined with other devices to measure static pressure in order to calculate total head. A velocity meter typically offers a direct measurement of flow velocity but does not provide insights into static or total head.

Therefore, the manometer's ability to gauge static, dynamic, and total head universally makes it the appropriate device for this scenario