What are the main types of flow meters used in process industries?

Differential pressure: orifice plate (most common, simple, permanent loss), Venturi (lower loss, higher cost), flow nozzle. Velocity: turbine (high accuracy for clean liquids), vortex (wide rangeability), ultrasonic (non-invasive), magnetic (conductive liquids only). Mass flow: Coriolis (direct mass measurement, most accurate), thermal dispersion (gases). Selection depends on fluid properties, accuracy needs, rangeability, pressure drop tolerance, and maintenance requirements.