Thermal mass flow controller DFC

for gasdigitalanalog

DFC programmable thermal mass flow controller with digital signal processing Design Features odigital and analog modes operate oprogrammable flow configurations oavailable flow ranges starting from 0 to 10 sccm up to 0 to 100 slpm omaximum pressure of 1000 psig (70 bars) omulti-drop capability of up to 256 units ostores calibration data for up to 10 gases ototalizer indicates total gas quantity oalarm limits for high and low gas flow oconversion factors for up to 256 gases oauto tune function for optimum control response oself diagnostic tests DFC digital mass flow controller Microprocessor driven digital flow controllers allow one to program, record, and analyze flow rates of various gases with a computer via an RS-485 interface (optional RS-232 is available). Controllers can be programmed for various control functions including flow set point, totalizer, stop totalizer, read totalizer, totalizer from preset flow, stop at preset total, auto zero, and more. 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.