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Reading Gas Mass Flow with the Gas Mass Flowmeters

Reading Gas Mass Flow with the Gas Mass Flowmeters

The FMA1700A/1800A Series electronic gas mass flow meters measure the flow of a variety of gases from 10 SCCM up to 1000 SLM. The FMA1700A/1800A uses heat transfer through a heated tube to measure molecular gas flow rate, and provides measurement of direct gas mass flow rate without compensating for differences in gas pressure or temperature (within stated limits).

These electronic gas mass flow meters are available in a cost-effective brass/aluminum construction for typical gas flows and a 316 SS construction for applications needing extra corrosion resistance.

The FMA1700A series without integral display is provided with a field selectable analog 0 to 5 Vdc or 4 to 20 mA output for remote monitoring; the FMA1800A series comprises of both an integral 3½ digit display and analog output. It is possible to tilt the display over 90° for viewing convenience. The display is calibrated standard to directly read out in SLM or SCCM for nitrogen (other gas calibrations available on special order).

The FMA1700A/1800A Series are considered to be suitable substitutes for several rotameter applications because of their analogue output capability, digital display, low cost, and insensitivity to variations in gas temperature and pressure. The FMA1800A Series are ideal to test air sampling equipment or in-the-field calibration of flowmeters when used with the FMA178BP portable battery pack.

The FMA178BP battery pack comes with a recharger, batteries, and a carrying case with a belt loop and shoulder strap. The FMA178BP enables the flowmeter to function in excess of 40 hours; and it is also possible to recharge the batteries at least 200 times.

The FMA1700A/1800A Series need 12 to 26 Vdc power @ 200 mA maximum, which can be provided by the FMA178PW plug-in socket power supply. The electronics have externally accessible fusing and are reverse polarity protected.

Model number FMA178C (supplied separately) provides a mating 9-pin “D” connector with 1 meter of ribbon cable to analyze the 0 to 5 Vdc output signal and power input connections (use FMA178C-MA for 4 to 20 mA output signal connection).

The LCD supplied with the FMA1800A Series is coupled to the lower electronics through a modular plug. It is possible to remotely locate the LCD by purchasing an FMA18RC remote cable assembly. Users must then build their own assembly for panel mounting the LCD.

  • NIST traceable calibration included
  • Tilting LCD display for effortless reading
  • Available in economical aluminum or corrosion-resistant 316 SS
  • Reads gas mass flow without pressure or temperature compensation


The key specifications of the gas mass flow meters are as follows:

  • Pressure Coefficient: 0.01% of full scale per psi (0.07 bar)
  • Temperature Coefficient: 0.15% of full scale per °C or better
  • Repeatability: ±0.5% of full scale and for units ≥100 scm from 0 to 20% of range
  • Accuracy: ±1.5% of full scale, including linearity over 15 to 25 °C and 5 to 60 psia (0.35 to 4.2 kg/cm2)
  • Response Time: 800 msec time constant; 2 seconds (typical) to within ±2% of set flow rate over 25 to 100% of full scale
  • Gas and Ambient Temperature: 0 to 50 °C
  • Power Requirements: 12 to 26 Vdc power @200 mA maximum
  • Leak Integrity: 1 x 10-9 std cc/sec of helium maximum to outside environment
  • Maximum Gas Pressure: 1000 psig (70 kg/cm2 gauge) for ranges up to 100 SLM; 500 psig (35 kg/cm2 gauge) above 100 SLM; 20 psig optimum
  • Compliance: EN55011 class 1, class B; EN50082-1
  • Shipping Weight: 1.1 kg
  • Transducer Power: 12 Vdc @ 200 mA maximum (FMA178PW)
  • Materials in Fluid Contact:
    • Stainless Steel models: 316 SS and FKM O-rings
    • Aluminum models: Anodized aluminum, 316 SS, brass and FKM O-rings
  • Output Signal
    • Linear 0 to 5 Vdc: 1000 Ω minimum load
    • 4 to 20 mA: 50 to 250 Ω loop resistance

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