Gas flow control scheme in dynamic gas calibrators

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A dynamic gas calibrator is a high-precision dynamic gas mixing instrument used to generate standard gases of different concentrations for calibrating various gas analyzers. It consists of a flow control system, a gas path control system, and a computer control system. Compared to traditional calibration methods, the dynamic gas calibrator enables automated and sequential operations, saving time and calibration gases while reducing the workload. It features flow calibration with a mass flow controller, a sequence setting function, and supports automatic calibration in conjunction with analysis instruments. It is widely used in the calibration of various gas detection instruments, such as combustible gas detectors, hydrogen detectors, oxygen detectors, etc. Dynamic gas calibrators utilize gas dynamic mixing technology; multiple gases are mixed together to create a gas mixture with a specific concentration, and the desired gas concentration is achieved by adjusting the mixing ratio. During the calibration process, the dynamic gas calibrator injects a mixed gas into the gas detection instrument to be calibrated, and precise calibration is achieved by comparing the response results of the detection instrument. During the calibration process, the dynamic gas calibrator is capable of producing high-precision, stable mixed gases, thereby improving the accuracy and stability of gas detection instruments. When controlling the gas flow for calibration, ensure that the flow control device of the dynamic gas calibrator is functioning properly. According to the calibration requirements and instrument specifications, set an appropriate gas flow rate to ensure accurate calibration results. The MFC4000, a compact and high-performance gas mass flow controller from the American company Siargo, available on the Industrial Components Network, can be used. The American Siargo gas mass flow controllers feature a compact size and high performance. The MFC4000 series is suitable for controlling the flow of non-corrosive gases, with a mass flow rate range of 50 mLn/min to 1000 mLn/min. It can be controlled using 0–5 VDC or 4–20 mA analog signals, or via RS485 Modbus digital signals. The control range can reach 100.1, and it can operate at pressures of 0.1–0.8 MPa and temperatures of 0–55°C. It features mechanical connections such as QUNF 10-32 internal threads or type 3 double-card connectors; other mechanical interfaces can also be customized. In terms of technology, the MFC4000 mass flow controller uses our company’s proprietary MEMS flow sensing chip, which integrates time-domain flow sensing technology with intelligent electronic technology. Compared with the traditional calorimetric flow sensing technology available on the market, this unique time-domain flow sensing technology eliminates the sensitivity to certain common gases. For other sensitive gases, software can be used to enable gas identification. The surface of the MEMS chip is passivated using silicon nitride ceramic material, combined with waterproof and oil-resistant nanocoatings, which significantly enhances the performance and reliability of the product. Time-domain flow sensing technology also provides better linearity and significantly reduces temperature effects. Note: mLn/min represents the standard flow rate under standard conditions (0°C, 101.325 kPa)