The three main principles involved in gas or liquid mass flow meters (MFM) and mass flow controllers (MFC)
The commonly used gas mass flowmeters or mass flow controllers in the market are mainly based on three fundamental principles: thermal principle, differential pressure principle, and Coriolis principle. For liquids, the main principles are differential pressure principle and Coriolis principle, while the thermal principle is less used for liquids. The thermal principle used for gases is further divided into three categories. A brief introduction is as follows:
1. The thermal principle is mainly divided into capillary thermal, insertion-type thermal, and microelectronic ( MEMS There are three types of thermal flow sensors. Although these three thermal types have different structures, their underlying principle is the same: using a sensor to detect the amount of heat carried away by the gas and then converting that information into the gas's mass flow rate.
Among these three types of thermal mass flow meters, the capillary thermal technology is more commonly used and has stronger adaptability to various operating conditions; many... big International brands all rely primarily on this principle—for example, Bronkhorst, Horiba, and many domestic brands as well utilize the capillary thermal flow principle.
2. Differential Pressure Type: The principle is to use Poiseuille's Law for compensation calculation. By measuring the pressure difference before and after the gas or liquid passes through a certain section of the pipeline, the volume flow rate of the gas can be calculated, and then converted to the flow rate under standard conditions.This is mainly represented by brands such as Alicat in the United States.(Here, the differential pressure type mainly refers to applications with small pipe diameters and small flow rates, and does not include orifice plate type differential pressure flow meters for large pipe diameters).This differential pressure principle is applicable to both gases and liquids, but its pressure resistance performance is slightly worse than that of the thermal type. Therefore, in scenarios with higher pressure, it is generally not recommended to use the differential pressure principle.
3. The Coriolis principle mass flowmeter operates on the following principle: As a fluid flows through the sensor circuit, a variable phase shift is induced by the Coriolis force. This phase shift is directly proportional to the mass of the fluid. In practice, the Coriolis mass flowmeter provides pure mass flow data with high accuracy. In real-world applications, it is widely used for measuring and controlling the flow rates of various liquids, as well as for mixed gases whose exact compositions are unknown, ultra-high-pressure gases, and fluid mixtures involving both gas and liquid phases.
In reality, the principle behind any product is only one of several factors that contribute to its superior performance. The quality and versatility of a gas mass flowmeter—its ability to perform well in various scenarios—depend on a wide range of considerations, including hardware technology, software technology, and manufacturing experience. For instance, even if a product employs an excellent principle, but its other supporting technologies are less than ideal, its overall performance might actually be inferior to that of a product built using conventional principles.
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