Measuring Clean Gases with Flowmeters

The differing pressures within a laminar flow field can be used by the FMA-LP2600A Series mass flow controllers to assess and manipulate mass flow rate of gases. The gas flow can be altered by the laminar flow element (LFE) within the meter, which enforces the streamlined flow. Within this component, the Poiseuille equation commands that the volumetric flow rate must be linearly related to the drop in pressure. Therefore, the reduction in pressure is measured between two fixed points of the LFE using a pressure sensor. In addition to this, the gas viscosity is also used to ascertain the volumetric flow rate. Additionally, absolute temperature and pressure sensors are integrated in order to adjust the calculated flow rate for standard conditions. This produces a standardized flow rate or mass flow rate with units of standard cubic centimeters per minute (SCCM) or standard liters per minute (SLM).

True proportional valves are used in order to control the stream of liquid utilizing the intrinsic PID loop controller. Principle readings consist of an output of 0 to 5V (4 to 20 mA optional) and RS232 communications. Customizable adjustments can be made to the gas-select component and the setpoints can be altered from the front keypad or using RS232 communications. The RS232 connection can be used to examine and document the measurement of volumetric flow, mass flow, absolute pressure, and temperature. The possibility of multi-dropping a maximum of 26 units on the same serial connection to a range of 46 meters (150').


  • Accuracy: ±(0.8% of reading + 0.2% FS)
  • Repeatability: ±0.2% FS
  • Turndown Ratio: 200:1
  • Control Response Time: 100 ms
  • Input Control Signal: 0 to 5 Vdc, RS232
  • Output Signal: 0 to 5 Vdc, RS232
  • Optional Input/Outputs: 4 to 20 mA, 0 to 10 Vdc
  • Operating Temperature: -10 to 50 °C (14 to 122 °F)
  • Zero Shift: 0.02%/ATM FS/°C
  • Span Shift: 0.02%/ATM FS/°C
  • Humidity Range: 0 to 100% RH, non-condensing
  • Excess Flow Rate: 2.4% FS
  • Wetted Materials: Standard: 303 and 302 SS, FKM, silicone RTV (rubber), glass-reinforced nylon, aluminum, brass, 410 SS, silicone, glass; >250 SLM: 416 SS and nickel replace brass
  • LSS (Option): 316LSS, 303SS, 430FRSS, Perfluoroelastomer standard, FKM, EPDM, Buna, Neoprene
  • Maximum Pressure: 50 psig
  • To Use in Volumetric Mode: Near atmosphere, 15 psig recommended maximum. Volumetric flow meters and controllers not certified for accuracy at mass flow rates above the rated flow range of the meter. They are designed for near atmospheric pressure conditions only. The recommended maximum operating pressure is 15 psig
  • Supply Current: 0.250 A for 20 SLM and under; 0.75 A for 50 SLM and above (typical)
  • Supply Voltage: 15 to 30 Vdc for units 2 SLM and smaller; 24 to 30 Vdc for units 5 SLM and larger
  • Electrical Connections: 8-pin circular mini DIN

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