MASS FLOW CONTROLLER WITH ENHANCED OPERATING RANGE

• US 20110247696A1
• Filed: 04/09/2010
• Published: 10/13/2011
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Smirnov, Alexei V., Zolock, Michael J.
• Granted Patent: US 8,499,786 B2
• Time in Patent Office: Days
• US Class Current: 137/2
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/0324 With control of flow by a condition or characteristic of a fluid
• 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
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A mass flow controller among other embodiments and method is described. The mass flow controller including a thermal mass flow sensor including at least two sensing elements coupled to a sensor tube of the mass flow controller, the thermal mass flow sensor being designed to provide a first signal indicative of flow of a gas within a first flow-rate-range and a second signal indicative of flow of the gas within a second flow-rate-range; and a control portion figured to control a valve position of the mass flow controller responsive to the first signal when the flow of the gas is within the first flow-rate-range and control the valve position of the mass flow controller responsive to the second signal when the flow of the gas is within a second flow-rate-range.

Claims

1. A mass flow controller comprising:

a sensor tube through which a portion of the gas flows when a gas is flowing through the mass flow controller;

first and second sensing elements coupled to the sensor tube at first and second locations of the sensor tube, respectively; and

a bridge circuit having first, second, third, and fourth nodes, a first predetermined resistive component being connected between the first and second nodes, a second predetermined resistive component being connected between the second and third nodes, the first sensing element being connected between the first and fourth nodes, the second sensing element being connected between the fourth and third nodes, the bridge circuit configured to provide a first signal from the second and fourth nodes and to provide a second signal from the first and third nodes; and

a control portion configured to control a valve position of the mass flow controller responsive to the first signal when the flow of the gas is within a first flow-range-rate and control the valve position of the mass flow controller responsive to the second signal when the flow of the gas is within a second flow-range-rate.

2. The mass flow controller of claim 1, including processing components between the bridge circuit and the control portion, the processing components selected from the group consisting of an amplifier and a digital to analog converter.

3. The mass flow controller of claim 1, wherein the control portion is configured to control the flow of the gas responsive to both first and second signals when the first and second ranges overlap.

4. The mass flow controller of claim 1, wherein the first and second sensing elements are sensing elements selected from the group consisting of:

resistance-thermometer elements and resistance temperature detectors.

5. The mass flow controller of claim 1, including a current source configured to provide a current to the first node of the bridge circuit, and wherein the first and second signals are voltage signals.

6. The mass flow control of claim 1, including a voltage source configured to apply a voltage at the first node, and wherein the first and second signals are current signals.

7. The mass flow controller of claim 1, wherein the control portion includes a component selected from the group consisting of an FPGA and a processor in connection with memory.

8. A mass flow controller comprising:

a thermal mass flow sensor including at least two sensing elements coupled to a sensor tube of the mass flow controller, the thermal mass flow sensor being designed to provide a first signal indicative of flow of a gas within a first flow-rate-range and a second signal indicative of flow of the gas within a second flow-rate-range; and

a control portion figured to control a valve position of the mass flow controller responsive to the first signal when the flow of the gas is within the first flow-rate-range and control the valve position of the mass flow controller responsive to the second signal when the flow of the gas is within a second flow-rate-range.

9. The mass flow controller of claim 8, including processing components between the thermal mass flow sensor and the control portion, the processing components including an amplifier and a digital to analog converter.

10. The mass flow controller of claim 8, including separate processing components to process the first and second signals.

11. The mass flow controller of claim 8, wherein the control portion is configured to control the flow of the gas responsive to both the first and the second signals when the first and second ranges overlap.

12. The mass flow controller of claim 8, wherein the thermal mass flow sensor includes a current source, and wherein the first and second signals are voltage signals.

13. The mass flow controller of claim 8, wherein the thermal mass flow sensor includes a voltage source, and wherein the first and second signals are current signals.

14. A method for operating a mass flow controller, comprising:

receiving a first input from a second and fourth nodes of a bridge circuit;

receiving a second input from a first and third nodes of the bridge circuit, the bridge circuit including a first predetermined resistive component being connected between the first and second nodes and a second predetermined resistive component being connected between the second and third nodes, a first sensing element being connected between a first and fourth nodes of the bridge circuit, and a second sensing element being connected between the fourth and third nodes of the bridge circuit, the first and second sensing elements coupled to a sensor tube at first and second respective locations of the sensor tube through which a portion of a gas flows when the gas is flowing through the mass flow controller;

controlling a valve position of the mass flow controller responsive to the first input when the flow of the gas is within a first flow-range-rate; and

controlling the valve position of the mass flow controller responsive to the second input when the flow of the gas is within a second flow-range-rate.

15. The method of claim 14, including:

amplifying the first and second inputs to create amplified inputs;

converting the amplified inputs to digital representations;

controlling the valve position based upon the digital representations of the first and second inputs.