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This post was last edited by liaifeng on 2020-7-29 20:55 The mass flow meter means that the volume of the fluid is a function of the fluid temperature and pressure, and is a dependent variable, while the quality of the fluid is a quantity that does not change with changes in time, space temperature, and pressure. As mentioned before, the flow measurement value of commonly used flow meters, such as orifice flow meters, laminar flow mass flow meters, turbine flow meters, vortex flow meters, electromagnetic flow meters, rotor flow meters, ultrasonic flow meters and elliptical gear flow meters, is the volume flow rate of the fluid. The fluid volume involved in activities such as scientific research, production process control, quality management, economic accounting, and trade transfer is generally mostly mass. Using the above-mentioned flow meter to only measure the volume flow rate of the fluid often cannot meet people's requirements. Usually, it is also necessary to try to obtain the mass flow rate of the fluid. In the past, the quality of the fluid could only be obtained indirectly through correction, conversion and compensation methods after measuring parameters such as temperature, pressure, density and volume of the fluid. This measurement method has many intermediate links, making it difficult to ensure and improve the accuracy of mass flow measurement. With the development of modern science and technology, some measurement methods and devices that directly measure mass flow have emerged, thus promoting the progress of flow measurement technology. A mass flow meter is an instrument used to measure linear, nonlinear, mass or volume flow of liquids or gases. When selecting a flow meter, you need to consider some site-specific intangible factors, such as the familiarity of the factory staff with the flow meter, their experience with calibration and maintenance, spare parts availability, and the average time between historical failures. It is also recommended to calculate the installation costs after completing the above steps. One of the most common flow measurement mistakes is to reverse the order of these steps: Sensor products that should be used normally should be selected, but their suitability is judged based on price. Those "inexpensive" products can come with expensive installation costs. This page will help you better understand flow meters, but feel free to contact our applications engineers if you have any specific flow measurement challenges. According to the measurement objects, there are two categories: closed pipes and open channels; according to the measurement purpose, they can be divided into total measurement and flow measurement, and the instruments are called total meters and flow meters respectively. The total meter measures the flow rate flowing through the pipe within a period of time. It is expressed as the total amount flowing in a short period of time divided by the time. In fact, the flow meter is usually equipped with a cumulative flow device and is used as a total meter, and the total meter is also equipped with a flow signaling device. Therefore, it is no longer practical to separate the flow meter and the total meter in a strict sense. Classification by measurement principles 1. Mechanical principles: Instruments belonging to this type of principle include differential pressure type and rotor type using Bernoulli's theorem. ； Impulse type and movable tube type using momentum theorem ； Direct mass formula using Newton's second law ； Target type using the principle of fluid momentum ； Turbine type using angular momentum theorem ； Vortex type and vortex type using the principle of fluid oscillation ； Pitot tube type that utilizes the total static pressure difference, as well as volumetric type, weir type, trough type, etc. 2. Electrical principles: Instruments used for this type of principle include electromagnetic type, differential capacitance type, inductance type, strain resistance type, etc. 3. Acoustic principles: There is an ultrasonic type that uses acoustic principles for flow measurement. Acoustic type (shock wave type), etc. 4.Optical principles: Laser type, photoelectric type, etc. are instruments belonging to this type of principle.