Aalborg GFM Thermal Mass Flowmeter


GFM mass flow meter
Thermal mass flow meter for gases is a low-cost solution. The GFM model mass flow meter produced by Aalborg is offered for flow measurement of gases passing through the line.
The GFM design combines the convenience and accuracy of traditional mass flow devices with previously unachievable low costs. Each of these thermal mass flow meters is constructed of aluminum and brass for non-corrosive gases or 316 stainless steel for corrosive applications. It also includes an advanced "U" shaped tube sensor along with flow transition elements.

Working Principles
The measured gases are separated into two laminar flow paths, one through the primary flow channel and the other through a capillary sensor tube. Both flow channels are designed to provide laminar flow and therefore the ratio of flow rates is constant. Two sensitive temperature sensing coils on the sensor tube are heated, and when flow occurs, the gas carries heat from the upstream to the downstream coils. The resulting temperature difference is proportional to the change in resistance of the sensor windings. A Wheatstone bridge design is used to monitor the temperature-dependent resistance gradient in the sensor windings, which is linearly proportional to the instantaneous flow rate. Output signals of 0 to 5Vdc and 4 to 20mA are generated and indicate mass molecular basis flow rates of the measured gas.
Flow rates are not affected by temperature and pressure changes within specified limitations.

General description
Compact, self-contained GFM mass flow meters are designed to read flow rates of gases. Robust design combined with instrumentation grade accuracy provides versatile and economical flow control tools. Aluminum or stainless steel models are available with engineering units (standard) or 0 to 100 percent display reading options.
The mechanical layout of the design includes an LCD readout display built into the top of the transducer. This reading module can be tilted over 90 degrees to provide optimum reading comfort. It connects to the transducer via a standard modular plug and can also be easily removed for remote reading installations. Converters without LCD readout are offered for OEM applications. GFM mass flow meters are available in Gas flow ranges from 10 sccm to 1000 sL/min. Gases are connected via 1/4” 3/8” 1/2” compression fittings and 3/4” FNPT fittings. Optional fittings are available. These controllers can be used as benchtop units or mounted to the base via screws.
Converter power supply ports are fused and also polarity protected.

Leak Integrity
1 x 10 -9 smL/sec maximum helium to external environment

Technical properties

  • Brand / Model Aalborg / GFM17, GFM37, GFM47, GFM57, GFM17,
  • Analog Output 4-2mA, 0 - 5 VDC
  • Digital Output RS485, RS232 Optional
  • Sensitivity ± (1.0 % ) F.S GFM 17, 37, 47 ± (1.5 % ) F.S GFM 57, 67, 77
  • Sampling Time 2 sec. Within ±2% of actual flow rate over F.S 25% to 100%
  • Ambient temperature 0….50°C
  • Measurement Gases Almost All Gases
  • Supply Voltage 12- 26V DC
  • Protection Class IP 65
  • Operating temperature -20…60°C
  • Display LCD(opt.) 90 ° Up-Down Movable
  • Pressure GFM 17, 37, 47: 70 bar maximum GFM 57, 67, 77: 34.5 bar
  • Measurement Range 0 -10ml/min to 0-1000 L/min
  • Line Diameter 1/4" - 3/4" F NPT