Patent ID: 9471066
Filing Date: 2016-10-18
CPC Classification: G01F,G05D,Y10T

Claim Text:
1. A mass flow controller comprising: a pressure-based flow meter constructed and arranged to measure the flow rate of mass through the mass flow controller; a thermal-based flow meter constructed and arranged to measure flow rate of mass through the mass flow controller; a control valve constructed and arranged so as to control the flow rate of mass through the mass flow controller in response to a control signal generated as a function of the flow rate as measured by one of the flow meters; an inlet for receiving a gas; and a system controller constructed and arranged to (a) generate the control signal as a function of the flow rate as measured by the thermal-based mass flow meter when the measured flow rate is relatively low and there are no pressure disturbances at the inlet, (b) change so as to generate the control signal as a function of the flow rate as measured by the pressure-based flow meter when the measured flow rate is relatively low and there is a pressure disturbance, and (c) generate the control signal as a function of the flow rate as measured by the pressure-based flow meter when the flow rate is relatively high, so that the mass flow controller is relatively insensitive to inlet pressure perturbations.