Flow Meter Types: Working Principles, Applications and Selection Guide The main types of flow meters in use give engineers and industrial buyers the ability to measure liquids, gases or steam more accurately. Typical technologies are Coriolis, electromagnetic, ultrasonic, differential pressure, positive displacement, turbine, variable area and thermal mass meters. All are different and the choice depends on the fluid and flow range, accuracy, pipe size, temperature, pressure and installation conditions. Need help sourcing an industrial flow meter? Share your fluid, flow range, pipe size, pressure, temperature and output requirements with our independent sourcing team. Request a Quote Quick definition: An instrument used to measure the rate at which a fluid flows through a pipe or other system. The technology measures either volumetric flow, mass flow, velocity, displacement or a related physical property, depending on the technology. Main Flow Meter Types at a Glance There are several different types of flow meters which are based on various physical principles. A few instruments measure mass, others measure volumetric flow based on velocity, displacement or pressure difference. This comparison provides a practical introduction to their common uses. Technology Working principle Typical application Coriolis Measures tube movement caused by Coriolis forces Direct mass flow and density measurement Electromagnetic Uses electromagnetic induction in conductive liquids Water, wastewater and conductive chemicals Ultrasonic Uses acoustic transit time or Doppler shift Inline or non-invasive liquid measurement Vortex Detects vortices produced behind a bluff body Suitable liquid, gas and steam services Differential pressure Calculates flow from pressure drop across a restriction Liquid, gas and steam pipelines Positive displacement Counts repeated, known volumes of fluid Viscous liquids and controlled transfer Variable area A float rises inside a tapered tube Simple local indication How Different Flow Measurement Technologies Work Coriolis and Electromagnetic Meters Coriolis meters are direct mass flow meters that track the flow of one or more vibrating tubes. They are also able to give density information. Their limitations may include higher cost, weight and pressure-loss considerations, depending on the meter design and application. An electromagnetic meter generates a magnetic field across the measuring tube. A conductive liquid moving through that field produces a voltage related to velocity. Magnetic meters contain no obstruction in the flow path, but the fluid must have adequate electrical conductivity. Ultrasonic, Vortex and Differential Pressure Meters Ultrasonic meters use sound waves to determine velocity. Clamp-on versions can support non-invasive measurement, although pipe material, condition, fluid properties and installation quality affect performance. Vortex meters detect repeating vortices and may be considered for suitable liquid, gas or steam applications. Differential pressure systems use a primary element, such as an orifice plate or Venturi tube, to create a measurable pressure difference. These established flow measurement types may require sufficient straight pipe and can introduce permanent pressure loss. Turbine, Positive Displacement and Variable Area Meters Turbine meters relate rotor speed to fluid velocity and generally perform best with clean fluids and a stable flow profile. Positive displacement meters trap and count known volumes, making them useful for certain viscous liquids. Variable-area meters, also called rotameters, provide simple local indication through the position of a float. ZF Corporation lists practical measurement options such as a Parker flow meter rated from 5 to 55 L/min and a Parker S-Series variable-area liquid flow meter . Product suitability should always be verified using the complete datasheet. Mass Flow Versus Volumetric Flow Volumetric flow describes the volume passing a point per unit of time, such as litres per minute. Mass flow describes the mass passing that point, such as kilograms per hour. Because density changes with process conditions, temperature and pressure can affect the relationship between mass and volume. Selection tip: Do not assume one technology is universally the most accurate. Accuracy depends on the specified operating conditions, installation, calibration, flow profile and properties of the measured fluid. Industrial Applications and Product Industrial flow meters support water treatment, chemical processing, oil and gas, compressed air, HVAC, food production and manufacturing. Application scale varies significantly. For example, ZF Corporation lists a Honeywell HAF bidirectional airflow sensor for low airflow and a Parker SCFTT-Series meter rated up to 150 L/min for a different operating requirement. Buyers can browse the flow meters category and related flow indicators. The Flowserve brand page is provided for market and product resea…