What are the common methods for measuring fluid flow?

Flow measurement methods include: Differential pressure (orifice plate, venturi - measure pressure drop proportional to flow squared), Positive displacement (gear, piston meters - directly measure volume), Velocity (turbine, ultrasonic, electromagnetic - measure fluid velocity), Mass flow (Coriolis - measures mass directly, very accurate), and Vortex (count vortices shed from bluff body). Selection depends on fluid type, flow range, accuracy, cost, and installation constraints. Electromagnetic meters work only with conductive fluids.