What type of flow meter measures the mass of a fluid passing a point per unit time?

Mass flow meters are specifically designed to directly measure the mass of a fluid that passes through a given point over a unit of time. This capability is critical in applications where precise measurements of mass flow are required, such as in chemical processing, food and beverage production, and pharmaceuticals.

These meters operate based on the principle that mass and density can be used to calculate flow accurately, regardless of variations in temperature or pressure. By directly measuring mass flow, they eliminate the need for additional calculations or corrections that would be necessary when using other types of flow meters.

In contrast, the other types of flow meters listed focus on different measurement principles. Magnet flow meters measure the volumetric flow rate based on electromagnetic principles and require knowledge of the fluid's density to convert volume to mass. Ultrasonic flow meters use sound waves to determine flow rates, and positive displacement flow meters count the volumes of fluid using mechanically moving parts. While all of these meters have their specific applications and advantages, they do not measure mass flow directly as mass flow meters do.