Patent ID: 7136767

Claim:
A self-calibrating mass flow controller system comprising: a mass flow controller including a flow channel with an inlet and an outlet, a laminar flow element disposed within the flow channel in a bypass section, a sensor tube coupled at one end to the flow channel at a location upstream of the bypass section and at a second end to the flow channel at a location downstream of the bypass section, an outlet control valve disposed within the outlet, and one or more resistive elements disposed about the sensor tube, wherein the one or more resistive elements are each operable to produce an electrical measurement signal corresponding to a mass flow within the sensor tube; a variable gas flow source configured to supply gas to the mass flow controller; a receptacle of predetermined volume configured to receive gas from the variable gas flow source; a pressure differentiator configured to produce an electronic calibration signal representative of the time derivative of gas pressure within the receptacle; and an electronic control unit configured to receive the electrical measurement signal, adjust the measurement signal using the calibration signal, and control the outlet control valve.