Method Of Calibrating A Fluid-Level Measurement System

• US 20080243418A1
• Filed: 10/31/2007
• Published: 10/02/2008
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: Space Administration, The Government Of The United States Of America, As Represented By The Secretary Of The Navy
• Inventors: Woodard, Stanley E., Taylor, Bryant Douglas
• Granted Patent: US 7,711,509 B2
• Time in Patent Office: Days
• US Class Current: 702/100
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level

Abstract

A method of calibrating a fluid-level measurement system is provided. A first response of the system is recorded when the system'"'"'s sensor(s) is (are) not in contact with a fluid of interest. A second response of the system is recorded when the system'"'"'s sensor(s) is (are) fully immersed in the fluid of interest. Using the first and second responses, a plurality of expected responses of the system'"'"'s sensor(s) is (are) generated for a corresponding plurality of levels of immersion of the sensor(s) in the fluid of interest.

Claims

1. A method of calibrating a fluid-level measurement system having fluid level sensing means that generates a response based on the portion of said fluid level sensing means that is immersed in a fluid, said method comprising the steps of:

recording a first response of said fluid level sensing means when said fluid level sensing means is not in contact with said fluid of interest;

recording a second response of said fluid level sensing means when said fluid level sensing means is fully immersed in said fluid of interest; and

generating, using said first response and said second response, a plurality of expected responses of said fluid level sensing means for a corresponding plurality of fractional levels of immersion of said fluid level sensing means in said fluid of interest.

2. A method according to claim 1 wherein each of said first response, said second response, and said plurality of expected responses is frequency-based.

3. A method according to claim 1 wherein each of said first response, said second response, and said plurality of expected responses is capacitance-based.

4. A method according to claim 1 wherein each of said plurality of expected responses is determined in accordance with

${\omega }_{}$

E 

( L ) = ω

1 1 + ( ( ω

1 ω

2 ) 2 - 1 ) * L

where ω

_E(L) is an expected frequency response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels of immersion,

L is a fractional value indicative of one of said plurality of levels of immersion as compared to said fluid level sensing means being fully immersed in said fluid of interest,

ω

₁ is a frequency response comprising said first response, and

ω

₂ is a frequency response comprising said second response.

5. A method according to claim 1 wherein each of said plurality of expected responses is determined in accordance with

$C_E$

( L ) = C 1 1 + ( ( C 1 C 2 ) 2 - 1 ) * L

where C_E(L) is an expected capacitance response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels of immersion,

L is a fractional value indicative of one of said plurality of levels of immersion as compared to the fluid level sensing means being fully immersed in said fluid of interest,

C₁ is a capacitance response comprising said first response, and

C₂ is a capacitance response comprising said second response.

6. A method according to claim 1 wherein said steps of recording include the step of wirelessly interrogating said fluid level sensing means to record said first response and said second response.

7. A method of calibrating a fluid-level measurement system having fluid level sensing means that generates a response based on the portion of said fluid level sensing means that is immersed in a fluid, said method comprising the steps of:

providing a receptacle with said fluid sensing means mounted therein for detecting a level of said fluid of interest in the receptacle;

recording a first response of said fluid level sensing means when said receptacle is empty;

recording a second response of said fluid level sensing means when said receptacle is filled with said fluid of interest; and

generating, using said first response and said second response, a plurality of expected responses of said fluid level sensing means for a corresponding plurality of levels of said fluid of interest in said receptacle.

8. A method according to claim 7 wherein each of said first response, said second response, and said plurality of expected responses is frequency-based.

9. A method according to claim 7 wherein each of said first response, said second response, and said plurality of expected responses is capacitance-based.

10. A method according to claim 7 wherein each of said plurality of expected responses is determined in accordance with

${\omega }_{}$

E 

( L ) = ω

1 1 + ( ( ω

1 ω

2 ) 2 - 1 ) * L

where ω

_E(L) is an expected frequency response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels,

L is a fractional value indicative of one of said plurality of levels as compared to the receptacle being filled with said fluid of interest,

ω

₁ is a frequency response comprising said first response, and

ω

₂ is a frequency response comprising said second response.

11. A method according to claim 7 wherein each of said plurality of expected responses is determined in accordance with

$C_E$

( L ) = C 1 [ 1 + ( ( C 1 C 2 ) - 1 ) * L ]

where C_E(L) is an expected capacitance response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels,

L is a fractional value indicative of one of said plurality of levels as compared to the receptacle being filled with said fluid of interest,

C₁ is a capacitance response comprising said first response, and

C₂ is a capacitance response comprising said second response.

12. A method according to claim 7 wherein said steps of recording include the step of wirelessly interrogating said fluid level sensing means to record said first response and said second response.

13. A method of calibrating a fluid-level measurement system having wireless fluid level sensing means that generates a response based on the portion of said wireless fluid level sensing means that is immersed in a fluid wherein said response so-generated is one of a frequency response and a capacitance response, said method comprising the steps of:

providing a receptacle with said wireless fluid sensing means mounted therein for detecting a level of a fluid of interest in said receptacle;

recording a first response of said wireless fluid level sensing means when said receptacle is empty,

recording a second response of said wireless fluid level sensing means when said receptacle is filled with said fluid of interest; and

generating, using said first response and said second response, a plurality of expected responses of said wireless fluid level sensing means for a corresponding plurality of levels of said fluid of interest in said receptacle.

14. A method according to claim 13 wherein said response so-generated by said wireless fluid level sensing means is a frequency response, and wherein each of said plurality of expected responses is determined in accordance with

${\omega }_{}$

E 

( L ) = ω

1 1 + ( ( ω

1 ω

2 ) 2 - 1 ) * L

where ω

_E(L) is an expected frequency response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels,

L is a fractional value indicative of one of said plurality of levels as compared to said receptacle being filled with said fluid of interest,

ω

₁ is a frequency response comprising said first response, and

ω

₂ is a frequency response comprising said second response.

15. A method according to claim 13 wherein said response so-generated by said wireless fluid level sensing means is a capacitance response, and wherein each of said plurality of expected responses is determined in accordance with

$C_E$

( L ) = C 1 [ 1 + ( ( C 1 C 2 ) - 1 ) * L ]

where C_E(L) is an expected capacitance response comprising one of said plurality of expected responses associated with a corresponding one of said plurality of levels,

L is a fractional value indicative of one of said plurality of levels as compared to said receptacle being filled with said fluid of interest,

C₁ is a capacitance response comprising said first response, and

C₂ is a capacitance response comprising said second response.

16. A method of calibrating a fluid-level measurement system having fluid level sensing means that generates a response based on the portion of said fluid level sensing means that is immersed in a fluid, said method comprising the steps of:

(i) recording and storing a first response of said fluid level sensing means when said fluid level sensing means is not in contact with said fluid of interest;

(ii) recording and storing a second response of said fluid level sensing means when said fluid level sensing means is fully immersed in said fluid of interest;

(iii) recording and storing one or more additional intermediate responses of said fluid level sensing means wherein each said intermediate response corresponds to a particular additional level of immersion of said fluid level sensing means in said fluid of interest;

(iv) repeating the above steps (i), (ii) and (ii) for a range of fluid dielectric values of interest;

(v) measuring and recording an in-field first response and an in-field second response;

(vi) retrieving from said plurality of stored first and second responses and their respective fractional levels, the pair (or pairs) of said stored first and second responses that is nearest in value to said in-field first and second responses;

(vii) retrieving said stored intermediate responses and their respective fractional levels that correspond to said retrieved first and second responses;

(viii) using an interpolation means to generate in-field intermediate responses from said first retrieved response, said second retrieved response and all said intermediate retrieved responses and their corresponding fractional levels; and

(ix) generating, using said in-field first response, said second in-field second response, and said interpolated intermediate responses, a plurality of expected responses of said fluid level sensing means for a corresponding plurality of fractional levels of immersion of said fluid level sensing means in said fluid of interest.

17. A method according to claim 16 wherein each of said first response, said second response, said one or more intermediate responses, and said plurality of expected responses is frequency-based.

18. A method according to claim 16 wherein each of said first response, said second response, said one or more intermediate responses, and said plurality of expected responses is capacitance-based.

19. A method according to claim 16 wherein each of said plurality of expected responses is determined in accordance with an interpolating polynomial.

20. A method according to claim 16 wherein said steps of recording include the step of wirelessly interrogating said fluid level sensing means to record said first response, said second response, and said intermediate responses.

22. A method of calibration of a fluid-level measurement system having fluid level sensing means that generates a response based on the portion of said fluid level sensing means that is immersed in a fluid, said method comprising the steps of:

(i) recording and storing a first response of said fluid level sensing means when said fluid level sensing means is immersed in said fluid of interest at a first reference level;

(ii) recording and storing a second response of said fluid level sensing means when said fluid level sensing means is immersed in said fluid of interest at a second reference level;

(iii) recording and storing one or more additional intermediate responses of said fluid level sensing means wherein each said intermediate response corresponds to a particular level of immersion of said fluid level sensing means in said fluid of interest;

(iv) repeating the above steps (i), (ii) and (ii) for a range of fluid dielectric values of interest;

(v) generating, using said first stored response, said second stored response, and said one or more intermediate stored responses, a plurality of expected responses of said fluid level sensing means for a corresponding plurality of fractional levels of immersion of said fluid level sensing means in said fluid of interest;

(vi) generating and storing a separate calibration curve for each fluid dielectric using said first stored response, said second stored response, said one or more intermediate stored responses, and said plurality of expected responses;

(vii) measuring a first in-field response and a second in-field response; and

(viii) utilizing the stored calibration curve having a first response and a second response closest to said in-field measured first and second responses.

23. A method according to claim 22 wherein each of said first response, said second response, said one or more intermediate responses, and said plurality of expected responses is frequency-based.

24. A method according to claim 22 wherein each of said first response, said second response, said one or more intermediate responses, and said plurality of expected responses is capacitance-based.