Fluid flow measurement correcting system and methods of constructing and utilizing same

• US 6,208,943 B1
• Filed: 11/19/1997
• Issued: 03/27/2001
• Est. Priority Date: 07/24/1996
• Status: Expired due to Term

• Current Assignee: American Sigma, Inc. (Danaher Corporation)
• Original Assignee: American Sigma, Inc. (Danaher Corporation)
• Inventors: Kaiser, Donald F., Lyndaker, David W., Randolph, Gary L., Liebe, John, Steen, Michael D., Tavano, Anthony J.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): NGUYEN, LINH M
• Application Number:
  US08/974,027
• Time in Patent Office: 1,224 Days
• Field of Search: 702/50, 702/100, 702/45, 702/47, 731/521.8, 137/386
• US Class Current: 702/47
• CPC Class Codes: G01F 1/002 wherein the flow is in an open channel
• CPC Class Codes: G01F 1/34 by measuring pressure or differential pressure
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift
• CPC Class Codes: G01F 23/165 of bubbler type
• CPC Class Codes: Y10S 239/03 Fluid amplifier
• CPC Class Codes: Y10T 137/7287 Liquid level responsive or maintaining systems

Abstract

An apparatus for calculating fluid flow in a channel including a very low profile probe which detects fluid depth in the channel; a mechanism for measuring average fluid velocity in the channel; a mechanism for correcting the detected fluid depth based upon the measured average fluid velocity to account for drawdown; and a mechanism for calculating average flow rate based upon the average fluid velocity measurement and the corrected fluid depth value. The probe has a height to width ratio of less than 0.52.

Claims

1. A method for measuring fluid flow in a channel, comprising the steps of:

obtaining a probe having a height to width ratio of less than 0.52, wherein said probe height and width are positioned substantially perpendicular to the direction of the main fluid flow in said channel;

obtaining a computing means having stored therein drawdown data for said probe;

placing said probe in a channel where fluid flow is to be measured;

determining fluid depth in said channel with said probe;

correcting said fluid depth determination based upon said drawdown data using said computing means; and

calculating fluid flow rate based upon said corrected fluid depth determination using said computing means.

2. A method as recited in claim 1, including the steps of:

measuring drawdown effects for said probe at a plurality of fluid velocities; and

storing said drawdown effect measurements for said probe in said computing means.

3. A method as recited in claim 2, wherein:

said drawdown storing step comprises the steps of curve fitting said drawdown measurements and storing an equation representing said curve fitted drawdown measurements in said computing means.

4. A method as recited in claim 3, including the steps of:

measuring average fluid velocity in the channel; and

recording said fluid velocity measurements in said computing means.

5. A method as recited in claim 1, wherein:

said correcting step occurs in real time following said fluid depth determining step.

6. A method as recited in claim 3, wherein:

said curve fitting step utilizes a least squares approximation.

7. A method as recited in claim 4, wherein:

said drawdown equation provides fluid level error as a function of fluid velocity; and

said correcting step comprises the step of providing said fluid level error as an offset to said fluid depth determination.

8. A method as recited in claim 4, further including the step of:

verifying that said fluid velocity measurement and said fluid velocity recording step have been completed before executing said correcting step.

9. A method as recited in claim 4, wherein:

said fluid depth correcting step and said flow rate calculating step execute substantially in real time.

10. An apparatus for calculating fluid flow in a channel, comprising:

a probe member having means for detecting a fluid level in the channel and having a height to width ratio of less than 0.52, wherein said probe height and width are positioned substantially perpendicular to the direction of the main fluid flow in said channel;

means for measuring fluid velocity in the channel;

means for correcting said fluid level detection to account for drawdown conditions acting on said probe member; and

means for calculating average fluid flow rate based upon said fluid velocity measurement and said corrected fluid level.

11. An apparatus as recited in claim 10, wherein:

said correcting means provides an offset fluid level value based upon said fluid velocity measurement.

12. An apparatus as recited in claim 10, wherein:

said correcting means corrects said fluid level detection substantially in real time.

13. An apparatus as recited in claim 11, wherein:

said apparatus includes computing means and associated memory; and

said correcting means comprises an equation stored in said memory, wherein said equation represents said offset fluid level value as a function of said fluid velocity as measured by said velocity measuring means.

14. An apparatus as recited in claim 11, wherein:

said apparatus includes computing means and associated memory;

said correcting means comprises a plurality of offset fluid level values being stored in said memory; and

said fluid velocity measurement is used to point to one of said offset fluid level values in said memory for correction of said fluid level detection.

15. An apparatus as recited in claim 10, wherein:

said probe member comprises a pressure transducer.

16. A device for measuring fluid parameters in a channel, comprising:

means for measuring a fluid level in the channel including a probe having a height to width ratio of less than 0.52, wherein said probe height and width are positioned substantially perpendicular to the direction of the main fluid flow in said channel;

memory means for storing drawdown data pertaining to said fluid level measuring means;

means for correcting said fluid level measurement based upon said drawdown data; and

means for calculating fluid flow rate based upon said corrected fluid level measurement.

17. A device as recited in claim 16, wherein:

said memory means stores drawdown data pertaining to said fluid level measuring means at a plurality of fluid velocities.

18. A device as recited in claim 17, further including:

means for measuring fluid velocity in the channel; and

wherein said correcting means corrects said measured fluid level based upon fluid velocity measured by said velocity measuring means.

19. A device as recited in claim 18, wherein:

said drawdown data comprises an equation for calculating a fluid level offset value based upon measured fluid velocity; and

said fluid level offset value is added to said measured fluid level by said correcting means.

20. A device as recited in claim 16, wherein:

said correcting means and said flow rate calculating means occur substantially in real time following said fluid level measurement.