Aalborg, GFC17A-VAL6-A0-3HD-02-SS, GFC Thermal Mass Flow Controller Aluminum, Viton-A Seals, 1/4" Compression, LCD Readout Display, Universal +12 VDC to 26 VDC Power, Local 0-5 VDC Input/Output Signal, Hydrogen H2 0-20, mL/Min, 14.7 psia Metering Pressure, 21.1 Deg C / 70 Deg F TemperatureGFC mass flow controllerModel GFC thermal Mass Flow Controllers are designed to indicate and control set flow rates of gases. The GFC combines the characteristics, and accuracy of conventional mass flow devices into a unique compact design at low costs previously unattainable. Zero and span adjustments are accessible from the outside of transmitters.Principles of OperationMetered gases are divided into two laminar flow paths, one through the primary flow conduit, and the other through a capillary sensor tube. Both flow conduits are designed to ensure laminar flows and therefore the ratio of their flow rates is constant. Two precision temperature sensing windings on the sensor tube are heated, and when flow takes place, gas carries heat from the upstream to the downstream windings. The resultant temperature differential is proportional to the change in resistance of the sensor windings. A Wheatstone bridge design is used to monitor the temperature dependent resistance gradient on the sensor windings which is linearly proportional to the instantaneous rate of flow. The closed loop control circuit continuously monitors the mass flow output and maintains it at the set flow rate. Flow rates are unaffected by temperature and pressure variations within stated limitations.General DescriptionCompact, self contained GFC mass flow controller is designed to indicate and control flow rates of gases. The rugged design coupled with instrumentation grade accuracy provides versatile and economical means of flow control. The valve is normally closed as a safety feature to ensure that gas flow is shut off in case of a power outage. These controllers may be used as benchtop units or mounted by means of screws in the base. Transducer power supply ports are fuse and polarity protected.