A mass flow controller (MFC) is a device used to measure and control the flow of

liquids A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

and

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

es. A mass flow controller is designed and calibrated to control a specific type of liquid or gas at a particular range of flow rates. The MFC can be given a setpoint from 0 to 100% of its full scale range but is typically operated in the 10 to 90% of full scale where the best accuracy is achieved. The device will then control the rate of flow to the given setpoint. MFCs can be either

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

or digital. A digital flow controller is usually able to control more than one type of fluid whereas an analog controller is limited to the fluid for which it was calibrated. All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the

mass flow sensor A mass (air) flow sensor (MAF) is a sensor used to determine the mass flow rate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit (ECU) to balance and deliver the co ...

and adjusts the proportional valve accordingly to achieve the required flow. The flow rate is specified as a percentage of its calibrated full scale flow and is supplied to the MFC as a voltage signal. Mass flow controllers require the supply gas or liquid to be within a specific pressure range. Low pressure will starve the MFC of fluid and cause it to fail to achieve its setpoint. High pressure may cause erratic flow rates. There are many different technologies which can help to measure the flow of the fluids and eventually help in controlling flow. Those technologies define the types of Mass Flow Controllers, and they include

differential pressure Pressure measurement is the measurement of an applied force by a fluid ( liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pres ...

(ΔP), differential temperature (ΔT),

Coriolis Coriolis may refer to: * Gaspard-Gustave de Coriolis (1792–1843), French mathematician, mechanical engineer and scientist * Coriolis force, the apparent deflection of moving objects from a straight path when viewed from a rotating frame of referen ...

, Ultrasonic, electromagnetic,

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...

, etc.

References

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External links

How a Mass Flow Controller works video

Thermal Mass Flow Meter / Controller (Principle of operation) video

MEMS-based thermal mass flow controller video
Measuring instruments Control devices

See also

References

External links