Mass flow controller with enhanced operating range
First Claim
1. A mass flow controller comprising:
- a sensor tube through which a portion of a gas flows when the gas is flowing through the mass flow controller;
first and second heating-sensing elements coupled to the sensor tube at first and second locations of the sensor tube, respectively; and
a single 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 heating-sensing element being connected between the first and fourth nodes, the second heating-sensing element being connected between the fourth and third nodes, the single 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 to process the first signal to generate a first flow-rate signal that is indicative of a flow rate of the gas, to obtain a measure of temperature-dependent drift in the second signal by measuring the second signal when the gas is not flowing through the sensor tube, and to process the second signal to subtract a contribution of the temperature-dependent drift from the second signal to generate a second flow-rate signal that is indicative of the flow rate of the gas, the first and second flow-rate signals collectively provide an indication of the flow rate over a larger flow-rate-range than either of the first and second flow-rate signals alone to control a valve position of the mass flow controller over the larger flow-rate-range.
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Accused Products
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.
24 Citations
14 Claims
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1. A mass flow controller comprising:
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a sensor tube through which a portion of a gas flows when the gas is flowing through the mass flow controller; first and second heating-sensing elements coupled to the sensor tube at first and second locations of the sensor tube, respectively; and a single 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 heating-sensing element being connected between the first and fourth nodes, the second heating-sensing element being connected between the fourth and third nodes, the single 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 to process the first signal to generate a first flow-rate signal that is indicative of a flow rate of the gas, to obtain a measure of temperature-dependent drift in the second signal by measuring the second signal when the gas is not flowing through the sensor tube, and to process the second signal to subtract a contribution of the temperature-dependent drift from the second signal to generate a second flow-rate signal that is indicative of the flow rate of the gas, the first and second flow-rate signals collectively provide an indication of the flow rate over a larger flow-rate-range than either of the first and second flow-rate signals alone to control a valve position of the mass flow controller over the larger flow-rate-range. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A mass flow controller comprising:
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a thermal mass flow sensor including a single bridge circuit including a first, second, third, and fourth nodes, at least two heating-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 a differential voltage between the second and fourth nodes and a second signal indicative of a top voltage at the first node; a differential voltage processing component to process the first signal to provide a digital representation of the differential voltage; a top voltage processing component to process the second signal to provide a digital representation of the top voltage; and a control portion to subtract contributions of temperature-dependent drift from the digital representation of the top voltage so the digital representation of the top voltage is indicative of the flow rate of the gas and to control a valve position of the mass flow controller using the digital representation of the differential voltage and the digital representation of the top voltage. - View Dependent Claims (9, 10, 11, 12)
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13. A method for operating a mass flow controller, comprising:
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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 heating-sensing element being connected between a first and fourth nodes of the bridge circuit, and a second heating-sensing element being connected between the fourth and third nodes of the bridge circuit, the first and second heating-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; processing the first input to generate a first flow-rate signal indicative of a flow rate of the gas within a first flow-rate-range; measuring the second input when there is substantially no flow of the gas through the sensor tube to obtain a measure of temperature-dependent drift in the second input; processing the second input to subtract a contribution of the temperature-dependent drift from the second input to generate a second flow-rate signal indicative of a flow rate of the gas within a second flow-rate-range; controlling a valve position of the mass flow controller responsive to the first and second flow-rate signals to control the valve position over a larger flow-rate-range than either of the first or second flow-rate-ranges. - View Dependent Claims (14)
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Specification