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What's special about the actual quality of gas? Focus on microfluidic control technology

The difference between gas volume, standard volume, and actual mass
Gas or liquid "flow measurement" is usually divided into the following categories:
Volume flow: refers to the size of the space occupied by the substance and can be regarded as "volume unit per unit time" (Example: l/min)
Molar Mass Flow: Usually referred to simply as “mass flow”, that is, the number of gas molecules per unit volume under a certain working condition. Under standardized conditions, it is expressed as “standardized unit volume per unit time” (example: standard l/min, l /minute)
Actual mass flow: refers to the measurement of the mass of a mole molecule, ie, the unit of mass per unit of time (eg, g/min)
Each of the above measurement modes has its application occasions, accompanied by an increase in measurement complexity, and the challenge for measurement technology is also upgraded one by one. The measurement of the actual mass flow is based on the fact that the degree of difficulty factor zui is high and the measurement cost is high.
Because of this, the benefits of user-selectable switchable units of measurement are particularly significant. The actual mass, standard (molar) mass, volumetric flow rate, etc., cover almost all common gas measurement units. In fact, the original multivariable measurement instrument was upgraded to a multi-function measurement and control device.
Why can not all mass flow meters measure the actual flow of gas?
Measurement of gas quality is an indirect measurement process that measures the power, weight, or heat capacity of the gas. There are several measurement methods, some of which apply only to flowing fluids. For example, a Coriolis mass flow meter measures fluid by measuring the difference in vibration caused by the fluid flowing through the pipe in a vibrating pipeline. flow. The measurement of the Coriolis principle is not affected by the type of fluid, whether the fluid is clean, or the thickness of the pipe, but the equipment is extremely expensive, several times the price of the Erikat mass flowmeter. In addition, this method can only measure the mass of the fluid. No other parameters, such as the molecular weight of the fluid flowing through the pipe, can be obtained because the device has no knowledge of the medium flowing through the pipe.
Upgrading the firmware version to 6v, the Ericcat mass flowmeter and mass flow controller can measure the actual mass of any gas or user-defined mixture in the preset gas list and output it in the specified measurement units. There are also other mass flowmeter brands on the market that have the function of measuring the actual mass flow, but they are only limited to known single gases. The usual practice is to preset a certain gas parameter in the device before leaving the factory, if the user wants to change other parameters. The gas must be returned to the original factory for re-setting. The reason is that there are no other gas viscosity data in this type of mass flow meter, so automatic compensation and correction cannot be performed. Once replaced with other gases, the original gas calibration traceability chain will fail. .
For Erikat mass flow meters and mass flow controllers, when a user switches gases, the device will automatically switch to the corresponding gas viscosity value, which is equivalent to recalibrating the device after switching gas. It is also based on this principle that as long as the gas switching is performed within the preset 98 to 130 gas lists, the Erikat mass flow meter and the mass flow controller do not suffer from the problem of accuracy degradation common to similar brands. The user can switch the mass flow meter to the actual mass measurement mode or switch the gas type at any time at the application site, and the accuracy of the device will always be the same. Users no longer need to purchase expensive Coriolis mass flow meters to measure the actual mass flow of gas.
Which applications require the actual mass flow of gas?
In the example of the biochemical reactor shown above, the system engineer will pay attention to the total amount of gas generated by the reaction (for example, the total amount of methane produced by the reaction). Such measurements are more intuitive in kilograms than in liters. Conversely, the reaction process in the chamber can be adjusted by controlling the mass flow, which is convenient for calculating the gas consumption and calculating the final output. For example, the total amount of gas produced by the reaction is 4 kg. In the next 24 hours, 2 kg of CO2 will be required to participate in the reaction.
The pharmaceutical industry uses a large variety of gases and liquids. A common application is hydrogenation for compounding films. The film thickness, film material density, mass, and film area are known to calculate the mass of gas that needs to participate in the reaction. Therefore, the standard volume of the gas is measured and then converted into gas quality. If the direct measurement of the reaction gas into the process system is possible The actual quality is much more convenient.

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