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What are the verification methods for mass flowmeters? Focus on microfluidic control technology

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 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 of the check, such as temperature and pressure, are inconsistent with the application conditions of the flowmeter;
3 The installation type of the flow meter is also very different from 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 flowmeter to the application conditions. There is no correction method for the typical viscosity correction, let alone some unmeasured factors (such as installation and flow regime). 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 closed 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 flowmeter is located must have the corresponding interface, valve and supporting recovery cleaning facilities, site and power supply.

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