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Mass flow meter online verification requirements - focus on microfluidic control technology

The mass flow meter directly measures the mass flow rate of the medium passing through the flow meter, and also measures the density of the medium and indirectly measures the temperature of the medium. The mass flow meter cannot control the flow rate. It can only detect the mass flow of liquid or gas, and output the flow value by analog voltage, current or serial communication. The mass flow meter is flexible, powerful, and cost-effective. It is a new generation flow meter. The mass flowmeter is based on Coriolis force. There are two parallel flow tubes inside the sensor, the drive coil is installed in the middle, the detection coil is installed at both ends, and the excitation voltage provided by the transmitter is applied to the drive coil. Perform a reciprocating cycle of vibration. The mass flow meter is a relatively accurate, fast, reliable, efficient, stable and flexible flow measuring instrument, which has been widely used in petroleum processing, chemical industry and other fields.
The most remarkable feature of the mass flow meter is that it can directly measure the mass flow rate of the medium, without being affected by factors such as pressure and temperature of the working state of the medium. At present, indirect mass flow calculations are also used as one type of mass flow meter in the industry. It features a pressure and temperature sensor while the flow sensor is working. The measured mass flow parameters are compensated by the parameters of the medium density as a function of temperature and pressure, thereby indirectly measuring the mass flow rate of the medium. Because it requires a complete and accurate compensation system, its complete set of instruments is more complicated. There are also many factors that cause measurement errors. Therefore, indirect mass flow meters are being replaced by mass flow meters in many applications.
Mass flow meters are generally only used for the measurement of liquid flow, and the verification for it is usually done in the laboratory (flow standard device) and its specific conditions, which is what we usually call offline verification. We know that the purpose of the mass flow meter verification is to determine the metering performance of the meter when it is actually used. The laboratory verification has the following problems: 1 The verification medium is different from the actual measured medium, and its physical parameters are different; 2 The working conditions such as temperature and pressure are inconsistent with the application conditions of the flow meter; 3 The installation type of the flow meter There are also big differences with the scene.
The above descriptions show that the verification or performance evaluation of the mass flowmeter in the laboratory is different from the actual performance of the flowmeter, which is far from the goal of accurate measurement. For example, when mass flow meters are used in custody transfer measurement, this difference is likely to be the source of disputes between buyers and sellers and must be eliminated.
Under the current technical conditions, it is difficult to correct the calibration conditions of the mass flowmeter to the application conditions. Typical methods such as viscosity correction have no correction method, let alone some unmeasured factors (such as installation and flow). State, etc.). Therefore, the best way to solve this problem is to perform an online verification of the mass flow meter.
The on-line verification of the mass flow meter is a solid liquid test. Compared with the laboratory test, it has many specialities or requirements. The main points are as follows:
(1) There must be a fixed or movable flow standard device for the verification mass flow meter. In addition to the accuracy of the device, the operating temperature range, pressure rating and medium compatibility of the device must also meet the online verification requirements. If it is a mobile traffic standard, it also requires the device to be light and flexible;
(2) During the verification process, the fluid must be in a sealed state to ensure that the verification conditions do not change, and at the same time ensure the safety of the verification site;
(3) The fluid is not allowed to be interrupted during the verification process;
(4) If the flowmeter to be inspected is verified by the mobile standard device, the site where the mass flowmeter is located must have the corresponding interface, valve and supporting recovery cleaning facilities, site and power supply.

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