Practical knowledge

Gas mass flow controller, abbreviated as MFC (Mass Flow Controller), is commonly used as a precise gas control device in industrial production, testing and analysis, scientific experiments and other processes. From a technical perspective, there are two mainstream gas mass flow controllers: thermal and laminar differential pressures. How to select a gas mass flow controller is mainly based on factors such as operating conditions and performance.

1. Medium, gas that needs to be measured and controlled. Gas mass flow controllers typically measure clean, pure gases (such as nitrogen, oxygen, air, etc.) or mixed gases. At present, most gas mass flow controllers can measure and control a single gas, while gas mass flow controllers based on the principle of laminar differential pressure can also measure and control mixed gases.

When selecting, it is necessary to clarify which gas to measure and confirm whether the selected gas mass flow controller can measure and control the gas. If it is a highly corrosive gas (such as chlorine, ammonia, etc.) or an explosive gas (such as hydrogen, methane, etc.), it is necessary to choose a corrosion-resistant or explosion-proof gas mass flow controller.

2. Pressure is a very important parameter when selecting a gas mass flow controller. Generally, the gas that can be measured and controlled by a gas mass flow controller is low-pressure gas with a pressure below 2MPa.

Inlet pressure, outlet pressure, and working differential pressure. Inlet pressure is the pressure before gas flows into the gas mass flow controller, outlet pressure is the pressure after gas flows out of the gas mass flow controller, and working differential pressure is the difference between inlet pressure and outlet pressure. The key points for selection are that the maximum working pressure of the gas mass flow controller should be greater than the inlet pressure, and the working differential pressure should be within the optional working pressure range of the gas mass flow controller.

3. Temperature, including medium temperature and ambient temperature. Users need to have a clear understanding of the actual temperature of the measured medium and the working environment temperature of the gas mass flow controller. The medium temperature range of the YIDU gas mass flow controller is -50 ℃~110 ℃, and the ambient temperature range is -40 ℃~50 ℃.

4. Traffic, namely minimum and maximum traffic. This flow rate refers to the standard condition flow rate, which is the flow rate under standard conditions. Standard conditions refer to operating conditions at a certain pressure (usually 101.325kPa) and temperature (usually 0 ℃, 15 ℃, 20 ℃, or 25 ℃).

After determining the flow range, the full range of the selected gas mass flow controller must be greater than or equal to the maximum flow rate, and the measurement and control range should cover the range between the minimum flow rate and the maximum flow rate. The commonly referred to gas mass flow controller refers to the full-scale flow rate of the gas mass flow controller.

5. Accuracy, i.e. maximum error. At present, the common accuracy of gas mass flow controllers is 1.0%, with higher accuracy of 0.5% and poorer accuracy of 1.5%. However, with the same 1.0% accuracy, there is also a difference between F.S. (full-scale accuracy) and S.P. (set value accuracy), with S.P. (set value accuracy) being better.

In addition to determining the accuracy value, it is also necessary to confirm whether the requirement is set value accuracy or full-scale accuracy when selecting a gas mass flow controller. In addition, most gas mass flow controllers have different accuracies in different flow ranges within the measuring range. For example, gas mass flow controllers have an accuracy of ± 1.0% S.P. in the range of 1% to 100%, and an accuracy of ± 0.2% F.S. in the range of 20% to 100%. Therefore, when selecting a gas mass flow controller, it is necessary to confirm the accuracy guarantee range to ensure that it meets actual needs.

6. Repeatability refers to the consistency between the results obtained from multiple consecutive measurements of the same measured quantity under the same measurement conditions. The YIDU gas mass flow controller can achieve a repeatability accuracy of ± 0.2% F.S., and the high-precision model can achieve a repeatability accuracy of ± 0.1% F.S.

7. Communication method, that is, what communication signal is used to operate the gas mass flow controller to achieve the purpose of controlling flow. The usual communication methods include analog signal control (such as 4-20mA, 0-5V, etc.) or digital signal control (such as RS485, Profibus, etc.).

In order to meet the convenient operation needs of university laboratories, the YIDU Gas Mass Flow Controller has specially developed a touch screen operation method, which can perform flow setting, medium switching and other operations on the panel.

8. Pipeline connection, including interfaces, connection methods, and pipe diameters, includes quick connect fittings, VCR fittings, sleeve fittings, and flanges according to the material, sealing, and pipe diameter requirements of the gas pipeline.

9. Installation method: Most gas mass flow controllers require horizontal or vertical installation, while YIDU gas mass flow controllers can be installed at any angle.

The user confirms the above information and can basically complete the selection of conventional gas mass flow controllers. Based on the working conditions, if there are special requirements such as response speed, pressuer drop, temperature drift, pressure drift, etc., further communication with engineers can be conducted according to the product performance description of the gas mass flow controller.