FLOW SENSOR SIGNAL CONVERSION

• US 20080000283A1
• Filed: 09/17/2007
• Published: 01/03/2008
• Est. Priority Date: 03/26/2003
• Status: Active Grant

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Celerity Incorporated (ICHOR Holdings, Ltd.)
• Inventors: Lull, John, Valentine, William, Wang, Chiun
• Granted Patent: US 7,720,617 B2
• Time in Patent Office: Days
• US Class Current: 73/1.16
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 15/024 involving digital counting
• CPC Class Codes: G01F 15/046 involving digital counting
• CPC Class Codes: G01F 25/10 of flowmeters
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

A method of obtaining at least one representation of a characteristic function of a sensor from a test fluid during calibration of the sensor according to a sensor model having a transfer function operating on flow rate, at least one sensor property and at least one fluid property and employing the at least one representation of the characteristic function to determine flow rates through the sensor during operation with an arbitrary fluid.

Claims

1-85. -85. (canceled)

86. A flow rate sensor comprising:

a conduit adapted to convey fluids and comprising a mass flow meter;

a bypass fluidly connected to the conduit; and

a processor operatively coupled to the mass flow meter and programmed to compensate for the behavior of a process fluid flowing through the bypass based at least partially on a flow signal from the mass flow meter and a bypass correction, wherein the bypass correction is based at least partially on at least one physical property of the conduit and a property of the process fluid.

87. The flow rate sensor according to claim 86, wherein the bypass correction is based at least partially on a Reynolds number of the process fluid flow.

88. The flow rate sensor according to claim 86, wherein the bypass correction is based at least partially on at least one physical property of the conduit and a viscosity of the process fluid.

89. The flow rate sensor according to claim 88, wherein the processor is further configured to generate a representation of the flow rate of the process fluid based on the bypass correction and the signal from the mass flow meter.

90. The flow rate sensor according to claim 89, wherein the bypass correction is further based on a characteristic function at least partially defined by a mapping of a plurality of flow responses of at least one calibration fluid.

91. A flow controller including a flow path, comprising:

a flow sensor adapted to provide a signal representative of a process fluid flowing through the flow path;

a processor operatively coupled to the flow sensor and configured to generate a drive signal based at least partially on the signal representative of the process fluid flowing through the flow path and a bypass correction that is based at least partially on at least one physical property of the conduit and at least one physical property of the process fluid;

a valve actuator adapted to receive the drive signal from the controller; and

a valve fluidly connected to the flow path and operatively coupled to the actuator to regulate flow of the process fluid through the flow path.

92. The flow controller of claim 91, wherein the bypass correction is based at least partially on a Reynolds number of the process fluid flow.

93. The flow controller of claim 91, wherein the bypass correction is based at least partially on at least one physical property of the conduit and a viscosity of the process fluid.

94. A method of controlling flow of a process fluid through a flow controller that includes a sensor conduit and a bypass, comprising:

providing a sensor output related to a flow rate of the process fluid through the sensor conduit;

generating a drive signal based at least partially on the sensor output and a bypass correction, the bypass correction based at least partially on one or more physical properties of the sensor conduit and one or more physical properties of the process fluid; and

regulating the flow of the process fluid through the flow controller based at least partially on the drive signal.

95. The method of claim 94, wherein the bypass correction is at least partially based on a Reynolds number of the process fluid flow.

96. The method of claim 94, wherein the bypass correction is at least partially based on a Reynolds number of at least one calibration fluid flowing through the flow controller during calibration.

97. A method of determining flow rates of a process fluid through a sensor conduit with a flow sensor including at least one representation of a characteristic function of the sensor obtained during calibration with a test fluid, the method comprising acts of:

providing a sensor output related to a flow rate of the process fluid through the conduit;

mapping the sensor output value to a characteristic value based on at least one first property of the process fluid;

obtaining an operand value including a flow rate component, at least one sensor property component and at least one fluid property component by indexing the at least one representation of the characteristic function with the characteristic value; and

determining the flow rate component of the operand value using at least one property of the sensor and at least one second property of the process fluid to provide an indication of the flow rate of the process fluid through the sensor conduit.

98. The method of claim 97, wherein the act of obtaining an operand value includes an act of obtaining an operand value such that the fluid property component is based at least in part on a Prandtl number of the test fluid.

99. The method of claim 97, wherein the act of obtaining an operand value includes an act of obtaining an operand value based at least in part on a product of a Reynolds number associated with flow through the sensor and a Prandtl number of the test fluid.

100. The method of claim 97, wherein the act of obtaining an operand value includes an act of obtaining an operand value such that the sensor property component is based at least in part on a Reynolds number associated with flow through the sensor, and wherein the act of obtaining an operand value includes an act of obtaining an operand value including a test fluid scale factor.

101. The method of claim 97, wherein the act of determining the flow rate component includes an act of separating the flow rate component from the operand value using at least one of a Reynolds number associated with sensor flow and a Prandtl number of the process fluid.

102. The method of claim 97, wherein a flow path of the sensor includes the sensor conduit and a bypass and the sensor includes calibration measurements including a test sensor response curve for the test fluid and a test total response curve for the test fluid.

103. The method of claim 102, further comprising an act of mapping the test sensor response curve to a process sensor response curve of the process fluid according to the representation of the characteristic function.

104. The method of claim 103, wherein the act of mapping the test sensor response curve includes mapping each of the sensor output values of the test sensor response curve to test characteristic values based on at least one first property of the test fluid.

105. The method of claim 104, wherein the act of mapping the test sensor response curve includes mapping each of the test flow rates of the test sensor response curve to operand values based on the at least one sensor property and at least one second fluid property.

106. The method of claim 105, wherein the act of mapping the test sensor response curve includes mapping each of the sensor output values comprising the test sensor response curve to process characteristic values base on the at least one first property of the process fluid.

107. The method of claim 106, wherein the act of mapping the test sensor response curve comprises:

determining for each process characteristic value an associated process operand value based on the first representation of the characteristic function; and

determining a process flow rate from each of the associated operand values based on the at least one sensor property and the at least one second process fluid property.

108. The method of claim 107, wherein the process flow rates and the test sensor output values form the process sensor response curve.

109. The method of claim 108, further comprising an act of dividing the test total response curve by the test sensor response curve to provide a bypass flow curve.

110. The method of claim 109, further comprising:

multiplying the bypass curve by the process sensor response curve to provide a process total flow response curve; and

providing a linearization curve configured to map values of the process total response curve substantially to a straight line.