SYSTEM FOR AND METHOD OF PROVIDING PRESSURE INSENSITIVE SELF VERIFYING MASS FLOW CONTROLLER

摘要

Mass flow controllers include pressure based flow meters, heat based flow meters, control valves and system controllers. Pressure-based flow meters and heat-based flow meters each measure mass flow through a mass flow controller. The control valve is generated as a function of the flow rate measured by the heat-based flow meter when the measured flow rate is relatively low, and in response to the control signal generated as a function of the flow rate measured by the pressure-based flow meter when the flow rate is relatively high. Control the flow rate. A comparison of the flow measurements of the two flow meters will be used to (a) detect pressure disturbances at low flow rates, and (b) detect when a thermal based flow meter is out of calibration so that a zero offset signal can be applied to the column based flow meter. I can.