Apparatus and method for pressure fluctuation insensitive mass flow control
AssigneeMKS Instruments, Inc.
InventorsAli Shajii, Nicholas Kottenstette, Jesse Ambrosina
Life of this patent
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Abstract
A mass flow controller includes a thermal mass flow sensor in combination with a pressure sensor to provide a mass flow controller that is relatively insensitive to fluctuations in input pressure. The pressure sensor and thermal sensor respectively provide signals to an electronic controller indicating the measured inlet flow rate and the pressure within the dead volume. The electronic controller employs the measured pressure to compensate the measured inlet flow rate and to thereby produce a compensated measure of the outlet flow rate, which may be used to operate a mass flow controller control valve.
Claims25
A mass flow sensor for operation with a mass flow controller that includes an outlet control valve for controlling fluid flow through the controller, comprising:
- a thermal mass flow sensor, including a sensor bypass, configured to sense the flow of fluid into the inlet of the controller;
- a pressures sensor configured to sense the fluid pressure in the volume between the thermal mass flow sensor bypass and the control valve;
- and
- an electronic controller configured to monitor the pressure sensed by said pressure sensor and to compensate the sensed inlet flow rate sensed by said mass flow sensor to thereby produce a compensated measure of the rate of fluid flow out of the controller.
A method of determining the outlet flow of fluid from a mass flow controller that includes an outlet control valve, comprising the steps of:
- A) sensing and providing an indication of the flow of fluid into the inlet of the controller with a thermal mass flow sensor that includes a sensor bypass;
- B) sensing and providing an indication of the fluid pressure in the volume between the thermal mass flow sensor bypass and the control valve;
- C) an electronic controller monitoring the indication of pressure sensed in step B) for a period of time to obtain at least two pressure indications;
- and
- D) the electronic controller compensating the indication of flow rate sensed in step A) based on the pressure monitored in step C).
A mass flow controller comprising:
- an outlet control valve;
- a thermal mass flow sensor, including a sensor bypass, configured to sense the flow of fluid into the inlet of the controller;
- a pressures sensor configured to sense the fluid pressure in the volume between the thermal mass flow sensor bypass and the control valve;
- and
- an electronic controller configured to monitor the pressure sensed by said pressure sensor and to compensate the sensed inlet flow rate sensed by said mass flow sensor to thereby produce a compensated measure of the rate of fluid flow out of the controller, the electronic controller further configured to employ the compensated measure of fluid flow out of the controller to produce a closed loop control signal for the outlet control valve.
Dependencies are inferred from the claim text.