SI-20FDR Gas Mass Flow Controller | High Accuracy – Low Differential Pressure

The SI-20FDR gas mass flow controller is a high-precision gas flow measurement and control device. It achieves an accuracy of ±0.5% of full scale and is suitable for controlling mass flow even with virtually no available system pressure.

The SI-20FDR series features two independently controllable valves connected in series: a main valve and a fine-tuning valve. A sophisticated control algorithm coordinates the opening and closing of these two valves, enabling rapid, stable, and high-precision control of gas flow.

★★★★★

  • Short delivery time
  • Better price
  • Customizable parameters

Features

  • Higher measurement control accuracy, typically achieving ±0.5% or even better precision.
  • Rapid response speed with dual valves working in tandem to quickly reach setpoints, significantly reducing overshoot and stabilization time.
  • Minimal or zero overshoot. This is one of the primary advantages of dual-valve MFCs, making them particularly suitable for pressure-sensitive applications.
  • Fine-tuning valves are specifically designed for precise adjustments, ensuring stable and accurate control at low flow rates (e.g., below 2% of full scale).

Specifications

SeriesSI-20FDR
ModelLCLMMCMMBCBMHCHM
Range0-（150，200，300…600）SLM0-（600,700…1200)SLM0-（1200,1500…4000)SLM0-（4000,4200…6000)SLM
Accuracy±0.5%F.S
Linearity±0.5%F.S
Repeatability±0.2%F.S
Operating Differential Pressure0.3~0.5MPa (Specified when ordering)
Response Time<0.2s<0.1s<0.2s<0.1s<0.2s<0.1s<0.2s<0.1s
Turndown Ratio50：1100：150：1100：150：1100：150：1100：1
Response Time<0.8s
Warm-up Time< 5s
Analog Output0～5V、4～20mA
Digital OutputRS232/485, MODBUS protocol
Power Supply24VDC
Communication ProtocolModbus、DeviceNet、profinet、ErtherCAT、profibus 
Operating Temperature0~50℃
Maximum Pressure Rating3MPa/10MPa (Specified when ordering) 
Electrical ConnectionDB9 port
Monochrome LCD DisplaySimultaneously displays flow rate and settings
Maximum Pressure Rating3MPa/10MPa
Leak Rate1×10-9Pa m³/S
Protection RatingIP40
Base MaterialStainless steel
Seal Materialfluororubber, nitrile rubber, EPDM, perfluoroether
Case ThreadG3/4 internal thread1 inch
ConnectionFerrule fittings, pagoda fittings, quick-connect fittings, VCR fittings, flanges, etc.  
  • SI-20FDR-LC Dimension
    SI-20FDR-LC Dimension
  • SI-20FDR-MC Dimension
    SI-20FDR-MC Dimension
  • SI-20FDR-HC Dimension
    SI-20FDR-HC Dimension
  • SI-20FDR-BM Dimension
    SI-20FDR-BM Dimension
  • SI-20FDR-BC Dimension
    SI-20FDR-BC Dimension

Gas Mass Flow Controller Working Principle

The SI-20FDR is a high-accuracy flowmeter/controller series with a measurement error of only ±0.5% of full scale. The series’s exceptional precision stems from its unique sensor probe, a sealed unit comprising two sensing elements—a velocity sensor and a temperature sensor—that automatically correct for the effects of temperature and pressure variations.

The instrument circuit heats the velocity sensor to a constant value above the gas/liquid temperature, then measures the cooling effect of the gas flow. Flow is calculated based on the principle that the electrical power consumed to maintain a constant temperature difference is proportional to the gas mass flow rate. Both sensors are standard-grade platinum resistance temperature detectors (RTDs), sealed within a stainless steel housing.

Gas Mass Flow Controller Application – Gas Mixing

A suitable gas source, a precise mass flow controller, and a pressure gauge can create a fast gas mixing system. Many applications choose to mix gases on-site because purchasing custom-mixed gases from gas suppliers is quite expensive. Purchasing only pure gases not only reduces costs but also allows users to adjust the composition percentages of the constituent gases according to application requirements, greatly increasing convenience. Furthermore, for safety reasons, custom-mixed gases are transported and stored in steel cylinders, which cannot be disposed of casually after use and sometimes must be returned to the gas supplier according to regulations. Using various pure gases for mixing is much more convenient.

High Accuracy Gas Mass Flow Controller

Using a Sino-Inst mass flow controller to control the flow rate of each pure gas source individually allows for rapid gas mixing and control of the synthesis percentage.

In dynamic systems, the mixing ratio of the gas mixture may not always be 75% gas A + 25% gas B. What if this mixing ratio is used today, then changed to 25% gas A + 75% gas B tomorrow, and then changed to 50% gas A + 50% gas B later? Carefully considering the gas mixing ratios that may be used in the future to determine the flow range is crucial when purchasing a mass flow controller for gas mixing projects.

Our Sino-Inst mass flow controller is preset with 98 to 128 commonly used gases, allowing users to switch on-site at any time. This eliminates the need to purchase multiple mass flow controllers that are limited to a single gas, greatly saving on your purchase costs.

Technical Support

A mass flow meter is purely a measurement device. It measures the rate of gas flow passing through it and provides an output signal corresponding to that flow. A mass flow controller combines a mass flow meter with a proportional control valve and control electronics. It not only measures the flow but also actively adjusts the valve to maintain the flow at a user-defined setpoint. A meter tells you how much is flowing; a controller ensures the correct amount is flowing.

Yes, but with a critical caveat. You must apply the correct Gas Correction Factor (GCF). The controller is calibrated on a specific gas (usually nitrogen). To use it with another gas (like argon or CO₂), you must multiply the controller’s reading or divide its setpoint by the GCF for the new gas. Most modern digital controllers have built-in libraries of gases, allowing you to simply select the gas from a menu, and the controller handles the conversion automatically. Using a controller with the wrong gas without correction will result in significant measurement errors.

The measurement principle itself is largely compensated for changes in gas temperature, but the onboard electronics are sensitive to ambient temperature. The control board and other components have a specified operating range (e.g., 0-50°C). Operating outside this range can cause the electronics to drift, leading to inaccurate readings or even failure. It is important to install the controller in an environment that respects these limits.

Zero drift refers to a situation where the controller indicates a small positive or negative flow even when there is absolutely no gas flowing. It can be caused by changes in mounting orientation, sensor aging, or contamination. Most digital controllers have a “Tare” or “Auto-Zero” function. Periodically, under a no-flow condition (by closing a shutoff valve upstream), you can execute this command. The controller will re-establish its true zero point, correcting for any drift and restoring accuracy at low flow rates.

No. The technology discussed here, based on the thermal properties of gases, is designed exclusively for gases. The heat transfer characteristics of liquids are vastly different, and attempting to use a gas MFC for a liquid will not work and will likely damage the instrument. There is a different class of instruments, called Coriolis mass flow controllers, that are used for measuring the mass flow of liquids.

Contamination is the primary failure mode for thermal MFCs. Particulates can clog the narrow sensor tube, causing the reading to become low, erratic, or drop to zero. Oil or other condensable vapors can coat the inside of the sensor tube, changing its heat transfer properties and causing a calibration shift. The best defense is diligent, multi-stage filtration installed directly upstream of the controller.

The turndown ratio signifies flexibility. A controller with a 100:1 turndown can accurately control flow over a range 100 times smaller than its maximum capacity. This is valuable for processes with varying demands, like starting up a reactor at a low flow and ramping to a high flow. It can allow a single controller to do a job that might have previously required two or three different-sized controllers, saving cost, complexity, and panel space.

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The SI-20FDR gas mass flow controller is a high-precision gas flow measurement and control device. Accuracy reaches ±0.5% of full scale. It is widely used in projects requiring precise flow control, such as those involving air, hydrogen, and nitrogen.

Equipped with a proprietary high-flow-capacity solenoid valve, it is suitable for controlling mass flow even with virtually no available system pressure. Low pressure differential ensures minimal impact on the system, achieving flow control near atmospheric pressure and shortening system response time.

We will customize valves and PID control functions according to your application parameters to ensure fast and stable control while maintaining low pressure loss.

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SI-20FDR Gas Mass Flow Controller | High Accuracy - Low DP

The SI-20FDR gas mass flow controller is a high-precision gas flow measurement and control device. It achieves an accuracy of ±0.5% of full scale and is suitable for controlling mass flow even with virtually no available system pressure.

Product SKU: SI-20FDR Gas Mass Flow Controller

Product Brand: Sino-Inst

Price Valid Until: 2099-09-09

Product In-Stock: PreOrder

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