APPARATUS AND METHOD FOR PRESSURE FLUCTUATION INSENSITIVE MASS FLOW CONTROL

• US 20100324743A1
• Filed: 08/31/2010
• Published: 12/23/2010
• Est. Priority Date: 06/24/2002
• Status: Active Grant

• Current Assignee: MKS Instruments Incorporated
• Original Assignee: MKS Instruments Incorporated
• Inventors: Kottenstette, Nicholas, Shajii, Ali, Ambrosina, Jesse
• Granted Patent: US 8,150,553 B2
• Time in Patent Office: Days
• US Class Current: 700/282
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/0396 Involving pressure control
• CPC Class Codes: Y10T 137/7759 Responsive to change in rate of fluid flow
• CPC Class Codes: Y10T 137/776 Control by pressures across flow line valve

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.

Claims

1. A system comprising

a plurality of flow paths, each between a gas inlet and an outlet, the system further comprising:

a mass flow controller for each of the flow paths, each mass flow controller including a mass flow sensor for sensing the mass flow along the respective flow path and a control valve, responsive to a control signal, for controlling the mass flow through the corresponding outlet;

a pressure sensor for each of the flow paths for measuring fluctuations in pressure of gas along the respective flow path; and

at least one process controller for generating each control signal as a function of the sensed mass flow and measured fluctuations in pressure of gas so as to provide a substantially constant flow of gas at each of the outlets irrespective of fluctuations in pressure of gas at the respective inlet.

2. A system according to claim 1, wherein each pressure sensor measures fluctuations in pressure of gas along the respective flow path, upstream from the corresponding control valve.

3. A system according to claim 1, wherein each pressure sensor measures fluctuations in pressure of gas in the dead space between the respective flow sensor and the corresponding control valve.

4. A system, defining a plurality of flow paths, each between a gas inlet and an outlet, the system comprising:

a mass flow controller for each of the flow paths, each mass flow controller including a mass flow sensor for sensing the mass flow rate along the respective flow path and a control valve, responsive to a control signal, for controlling the mass flow through the corresponding outlet;

a pressure sensor for each flow path for measuring fluctuations in pressure of gas along the corresponding flow path; and

at least one process controller for generating each control signal as a function of the sensed mass flow rate at the respective inlet and the measured fluctuations in pressure of gas so as to compensate the flow rate measured by the sensor at the corresponding inlet to more closely approximate the flow rate at the outlet.

5. A system according to claim 4, wherein the pressure sensor measures fluctuations in pressure of gas along the flow path, upstream from the control valve.

6. A system according to claim 5, wherein the pressure sensor measures fluctuations in pressure of gas in the dead space between the flow sensor and the control valve.

7. A control system for controlling the flow of gas in each of a plurality of flow paths, the control system comprising:

a mass flow controller for each of the flow paths constructed and arranged so as to receive fluid flowing from a inlet supply line, each mass flow controller including a thermal mass flow sensor and an outlet valve;

a pressure sensor for each of the flow paths; and

at least one process controller including at least one pressure sensor interface for coupling the controller to a respective pressure sensor, wherein the controller employs data obtained at the pressure sensor interface to compensate for fluctuations induced in the thermal mass flow sensor by pressure transients in the inlet supply line.

8. A control system according to claim 7, wherein the pressure sensor and pressure interface with respect to each flow path are used to monitor the pressure within the corresponding mass flow controller.

9. A control system according to claim 7, wherein each mass flow controller includes a dead volume, and the corresponding pressure sensor and pressure interface are used to monitor the pressure within the dead volume.

10. A control system according to claim 7, wherein the process controller includes a flow sensor interface for coupling the process controller to the thermal mass flow sensor.

11. A control system according to claim 10, further including a temperature sensor and a temperature sensor interface for each flow path for obtaining data representative of the temperature of the fluid flowing in the corresponding thermal mass flow sensor.

12. A control system according to claim 11, wherein each mass flow sensor includes an outlet and the process controller employs readings of temperature, pressure and mass flow obtained from the respective temperature sensor interface, pressure interface and flow sensor interface to produce a compensated mass flow reading that more closely reflects the mass flow at the outlet of the mass flow sensor than a reading from the thermal mass flow sensor alone provides.