Aalborg, AFC46S-VDN5-C0-3HD-40-SS, AFC Thermal Mass Flow Controller Stainless Steel, Viton-A Seals, 3/8" Compression, No Display, +15 VDC, 0-5 VDC / 0-5 VDC, Hydrogen H2 0-60 L/Min, 14.7 psia Metering Pressure, 21.1 Deg C / 70 Deg F Temperature
AFC mass flow controller
Model AFC mass flow controllers are designed to indicate flow rates and control set flow rates of gases, incorporates an advanced straight tube sensor in conjunction with flow passage elements constructed of stainless steel.
Principles of Operation
Metered 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. AFC mass flow controller include an electromagnetic control valve that allows to be set to any desired flow rate within the range of the particular model. The valve is normally closed as a safety feature to ensure that gas flow is shut off in case of a power outage. The controller may be used as benchtop unit or mounted by means of screws in the base. Transducer power supply ports are fuse and polarity protected.
