A rotameter, also known as a variable area flow meter, is a device used to measure the flow rate of a fluid in a closed conduit. It operates based on the principle of a variable area, where the area of flow passage changes in response to the flow rate of the fluid passing through it. The typical design of a rotameter includes a tapered tube, often made of glass or plastic, with a smaller diameter at the bottom and a larger diameter at the top. Within this tube is a float—a spherical or cylindrical object—positioned in the path of the flowing fluid. As the fluid flows through the tube, the float rises, indicating the flow rate.

Screw pumps, often known as progressive cavity pumps or single screw pumps, are positive displacement pumps used for transferring viscous or abrasive fluids in various industrial and commercial applications. The design of these pumps involves a helical rotor (the single screw) turning within a double helix stator, creating a series of sealed cavities that move the fluid axially along the screw's length. The operation of a screw pump involves the rotation of the helical rotor within the stator. As the rotor turns, it pushes the fluid through the cavities formed between the screw and the stator. This pushing action results in a smooth, non-pulsating flow of the fluid, making screw pumps suitable for handling shear-sensitive or delicate liquids.