IMPULSE ANALYSIS FOR FLOW SENSOR-BASED FLUID CONTROL SYSTEM

• US 20090234594A1
• Filed: 03/14/2008
• Published: 09/17/2009
• Est. Priority Date: 03/14/2008
• Status: Active Grant

• Current Assignee: Fresenius KABI USA LLC (Fresenius SE & Co. KGaA)
• Original Assignee: Fluidnet Corporation (Fresenius SE & Co. KGaA)
• Inventors: Kramer, Charles E., Kirkman, John M. JR., Vincent, Douglas E., Carlisle, Jeffrey A.
• Granted Patent: US 7,847,276 B2
• Time in Patent Office: Days
• US Class Current: 702/49
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 5/16886 for measuring fluid flow rate, i.e. flowmeters
• CPC Class Codes: G01F 1/28 by drag-force, e.g. vane type or impact flowmeter

Abstract

A method and apparatus are disclosed for using flow rate changes to extract additional information from an in-line flow sensor.

Claims

1. A method for determining a position of a movable flow sensor element of a flow sensor in a flow control system, the flow sensor being of a type having an axially-extending flow passageway for a liquid to be delivered by the flow control system, the movable sensor element being axially movable within the flow passageway in response to a first force exerted on the sensor element by the liquid as it passes through the flow passageway and in response to a second force exerted on the sensor element in a direction opposite the first force by a spring received within the flow passageway, the sensor reaching equilibrium position within the flow passageway when the magnitudes of the first and second forces are equal, the equilibrium position corresponding to a axial position within the flow passageway which varies with varying flow rate, the flow control system being of a type having a source of fluid driving pressure for driving the fluid through the flow passageway, the flow rate being responsive to variations in the fluid driving pressure, the method comprising:

illuminating a photosensitive pixel array with a light source, the photosensitive pixel array extending axially along the flow passageway and the sensor element disposed in an optical path between the light source and the photosensitive pixel array to generate a first set of pixel intensity values for the photosensitive pixel array, the first set of pixel intensity values representative of a first sensor element position corresponding to a first flow rate;

introducing an abrupt change in the fluid driving pressure;

illuminating the photosensitive pixel array with the light source to generate a second set of pixel intensity values for the photosensitive pixel array, the second set of pixel intensity values representative of a second sensor element position corresponding to a second flow rate;

calculating a difference between the first and second sets of pixel intensity values as a function of pixel position.

2. The method of claim 1, wherein the first and second sets of pixel intensity values are values representative of pixel voltages.

3. The method of claim 1, wherein the sensor element is an optically transmissive ball.

4. The method of claim 1, further comprising:

identifying a first pixel position corresponding to a maxima of the difference between the first and second sets of pixel intensity values and a second pixel position corresponding to a minima of the difference between the first and second sets of pixel intensity values, wherein the first pixel position is representative of one of the first sensor element position and the second sensor element position and the second position corresponds to the other of the first sensor element position and the second sensor element position.

5. The method of claim 4, further comprising:

using one or both of the first and second pixel positions to determine a rate of flow of the fluid in the flow control system.

6. The method of claim 4, further comprising:

calculating one or both of an axial distance between the first pixel position and the second pixel position and a rate of change of position of the sensor element between the first sensor element position and the second sensor element position.

7. The method of claim 6, further comprising:

correlating one or both of said axial distance between the first pixel position and the second pixel position and said rate of change of position of the sensor element between the first sensor element position and the second sensor element position with a viscosity.

8. The method of claim 7, wherein said correlating is performed by comparing one or both of said axial distance between the first pixel position and the second pixel position and said rate of change of position of the sensor element between the first sensor element position and the second sensor element position with known sensor element behavior for one or more fluids of known viscosity, said known sensor element behavior associated with said known viscosity.

9. The method of claim 7, further comprising:

inputting fluid identifying information;

determining an expected viscosity based on said fluid identifying information;

comparing said viscosity determined by said correlating with said expected viscosity;

if said viscosity is not within some predetermined threshold of said expected viscosity, outputting an indication of an error condition.

10. The method of claim 1, wherein the abrupt change in the fluid driving pressure is an abrupt increase in the fluid driving pressure.

11. An optical position measurement apparatus for determining a position of a movable flow sensor element of a flow sensor in a flow control system, the flow sensor being of a type having an axially-extending flow passageway for a liquid to be delivered by the flow control system, the movable sensor element being axially movable within the flow passageway in response to a first force exerted on the sensor element by the liquid as it passes through the flow passageway and in response to a second force exerted on the sensor element in a direction opposite the first force by a spring received within the flow passageway, the sensor reaching equilibrium position within the flow passageway when the magnitudes of the first and second forces are equal, the equilibrium position corresponding to a axial position within the flow passageway which varies with varying flow rate, the flow control system being of a type having a source of fluid driving pressure for driving the fluid through the flow passageway, the flow rate being responsive to variations in the fluid driving pressure, the apparatus comprising:

a light source and a photosensitive pixel array for illumination with said light source, the photosensitive pixel array extending axially along the flow passageway and the sensor element disposed in an optical path between the light source and the photosensitive pixel array;

a processor receiving signals from said photosensitive pixel array to generate a first set of pixel intensity values for the photosensitive pixel array, the first set of pixel intensity values representative of a first sensor element position corresponding to a first flow rate and a second set of pixel intensity values for the photosensitive pixel array, the second set of pixel intensity values representative of a second sensor element position corresponding to a second flow rate;

a source of pressurized air for introducing an abrupt change in the fluid driving pressure;

said processor calculating a difference between the first and second sets of pixel intensity values as a function of pixel position.

12. The apparatus of claim 11, wherein the first and second sets of pixel intensity values are values representative of pixel voltages.

13. The apparatus of claim 11, wherein the sensor element is an optically transmissive ball.

14. The apparatus of claim 11, further comprising:

said processor identifying a first pixel position corresponding to a maxima of the difference between the first and second sets of pixel intensity values and a second pixel position corresponding to a minima of the difference between the first and second sets of pixel intensity values, wherein the first pixel position is representative of one of the first sensor element position and the second sensor element position and the second position corresponds to the other of the first sensor element position and the second sensor element position.

15. The apparatus of claim 14, further comprising:

said processor using one or both of the first and second pixel positions to determine a rate of flow of the fluid in the flow control system.

16. The apparatus of claim 14, further comprising:

said processor calculating one or both of an axial distance between the first pixel position and the second pixel position and a rate of change of position of the sensor element between the first sensor element position and the second sensor element position.

17. The apparatus of claim 16, further comprising:

a database storing known sensor element behavior for one or more fluids of known viscosity and correlating said known sensor element behavior with viscosity.

18. The apparatus of claim 16, further comprising:

said processor determining viscosity by comparing one or both of said axial distance between the first pixel position and the second pixel position and said rate of change of position of the sensor element between the first sensor element position and the second sensor element position with said known sensor element behavior.

19. A flow sensor for a flow control system for controlling flow of a liquid, the flow control system having a flow passageway, the flow sensor comprising:

a sensor element movably positioned in the flow passageway, wherein a position of the sensor element in the flow passageway is responsive to a flow rate of the liquid in the flow passageway and to a viscosity of the liquid, and further wherein the flow rate is responsive to a fluid driving pressure and a systemic flow resistance in the flow control system;

a sensor for generating a signal representative of a position of the sensor element in the flow passageway; and

a processor coupled to the sensor for receiving the signal from the sensor before and after an abrupt change in the fluid driving pressure to calculate any one or more of;

the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure;

the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure;

a change in position of the sensor element in the flow passageway;

a rate of change in position of the sensor element in the flow passageway;

the flow rate before the abrupt change in the fluid driving pressure;

the flow rate after the abrupt change in the fluid driving pressure;

a change in the flow rate;

the viscosity of the liquid; and

the systemic flow resistance.

20. A method for determining flow information in a flow control system, the flow control system for controlling flow of a liquid, the flow control system having a flow passageway, a sensor element movably positioned in the flow passageway, and a sensor for generating a signal representative of a position of the sensor element in the flow passageway, wherein a position of the sensor element in the flow passageway is responsive to a flow rate of the liquid in the flow passageway and to a viscosity of the liquid, and further wherein the flow rate is responsive to a fluid driving pressure and a systemic flow resistance in the flow control system, the method comprising:

introducing an abrupt change in fluid driving pressure;

prior to introducing the abrupt change in fluid driving pressure, sampling the signal from the sensor to obtain a first measurement of sensor element position;

after introducing the abrupt change in fluid driving pressure, sampling the signal from the sensor to obtain a second measurement of sensor element position; and

determining a difference between the first measurement and the second measurement.

21. The method of claim 20, further comprising using said difference between the first measurement and the second measurement to calculate any one or more of:

the position of the sensor element in the flow passageway before the abrupt change in the fluid driving pressure;

the position of the sensor element in the flow passageway after the abrupt change in the fluid driving pressure;

a change in position of the sensor element in the flow passageway;

a rate of change in position of the sensor element in the flow passageway;

the flow rate before the abrupt change in the fluid driving pressure;

the flow rate after the abrupt change in the fluid driving pressure a change in the flow rate;

the viscosity of the liquid; and

the systemic flow resistance.