Patent ID: 7073392

Claim:
A mass flow controller having a control loop, the mass flow controller comprising: a flow meter adapted to sense fluid flow in a fluid flow path and provide a flow signal indicative of the mass flow rate in the flow path; a controller coupled to the flow meter and adapted to provide a drive signal based at least in part on the flow signal; a valve actuator adapted to receive the drive signal from the controller; a valve adapted to be controlled by the valve actuator and coupled to the fluid flow path; at least one pressure transducer to measure at least one pressure in a mass flow controller environment and to provide at least one pressure signal indicative of measurement of the at least one pressure; and at least one compensation means to receive the at least one pressure signal and to provide at least one compensation signal to the control loop to compensate for effects of pressure changes in the mass flow controller environment, wherein the control loop of the mass flow controller includes the flow meter, the controller, the valve actuator, and the valve; wherein the at least one pressure transducer measures an inlet pressure of the flow path and provides an inlet pressure signal; wherein the at least one compensation means includes a compensation filter to receive the inlet pressure signal and to construct a false flow signal from the inlet pressure signal; wherein the flow meter includes a flow sensor adapted to sense fluid flow in the flow path and adapted to provide a sensor output signal indicative of the sensed fluid flow; and wherein the flow signal is determined by subtracting the false flow signal from the sensor output signal.