Aalborg, GFM17A-VAN6-A0-3AB-01-SS, GFM Thermal Mass Flow Meter Aluminum, Viton-A Seals, 1/4" Compression, No Display, Universal +12 to +26 VDC, 0-5 VDC, Air 0-10, mL/Min, 14.7 psia Metering Pressure, 21.1 Deg C / 70 Deg F TemperatureGFM mass flow meterA low cost solution to thermal mass flow metering for gases is presented by Aalborg in introducing the model GFM mass flow meter line. The GFM design combines the convenience and accuracy of conventional mass flow devices with low costs previously unattainable.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. Flow rates are unaffected by temperature and pressure variations within stated limitations.General DescriptionCompact, self contained GFM mass flow meters are designed to read flow rates of gases. The rugged design coupled with instrumentation grade accuracy provides versatile and economical means of flow control. Transducer power supply ports are fuse and polarity protected.