ACOUSTIC FLUID PRESENCE/ABSENCE DETECTION

• US 20100141460A1
• Filed: 12/08/2008
• Published: 06/10/2010
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Ecolab USA Incorporated (Ecolab, Inc.)
• Original Assignee: Ecolab, Inc.
• Inventors: Tokhtuev, Eugene, Owen, Christopher J., Pilipchenko, Anna, Skirda, Anatoly, Slobodyan, Viktor
• Granted Patent: US 8,120,500 B2
• Time in Patent Office: Days
• US Class Current: 340/621
• CPC Class Codes: A61M 2205/3375 Acoustical, e.g. ultrasonic, measuring means
• CPC Class Codes: A61M 5/1684 by detecting the amount of infusate remaining, e.g. signalling end of infusion
• CPC Class Codes: G01F 23/0007 for discrete indicating and measuring G01F23/02 - G01F23/28 take precedence
• CPC Class Codes: G01F 23/2961 for discrete levels G01F23/2962 - G01F23/2968 take precedence

Abstract

An acoustic sensor detects presence and/or absence of fluid in a fluid delivery medium. The acoustic sensor detects fluid absence based on the difference of the speed of sound between air and a fluid. For example, the acoustic sensor may detect fluid absence based on a phase shift between acoustic signals transmitted through the fluid delivery medium when fluid is present as compared to acoustic signals transmitted through the fluid delivery medium when fluid is absent, e.g., when air or bubbles are present in the fluid delivery medium.

Claims

1. A method comprising:

generating an excitation signal having an excitation frequency;

emitting, in response to the excitation signal, an acoustic interrogation signal having the excitation frequency into a fluid delivery medium in which presence or absence of a fluid is to be determined;

receiving the acoustic interrogation signal transmitted through the fluid delivery medium and generating therefrom an acoustic signal output;

determining a phase shift between the acoustic signal output and the excitation signal; and

determining presence or absence of the fluid within the fluid delivery medium based on the phase shift.

2. The method of claim 1, further comprising comparing the phase shift with at least one predetermined threshold criteria.

3. The method of claim 1, further comprising detecting an out-of-product event when the at least one predetermined threshold criteria is satisfied.

4. The method of claim 1, wherein determining the phase shift comprises multiplying the excitation signal and the acoustic signal output and obtaining therefrom a DC output signal indicative of the phase shift between the acoustic signal output and the excitation signal.

5. The method of claim 1, wherein a frequency of the excitation signal is chosen such that an initial phase shift between the acoustic signal output and the excitation signal is between 25 degrees and 60 degrees when fluid is present.

6. The method of claim 1, wherein determining presence or absence comprises comparing the phase shift to a predetermined lower threshold criteria and a predetermined upper threshold criteria.

7. The method of claim 6, further comprising detecting an out-of-product event when the phase shift is between the predetermined lower threshold criteria and the predetermined upper threshold criteria.

8. The method of claim 1, further comprising generating an out-of-product alert when absence of fluid in the fluid delivery medium is determined.

9. The method of claim 8, wherein generating the out-of-product alert comprises generating at least one of a message to an external device, a visible indicator, or an audible indicator.

10. The method of claim 8, further comprising generating at least one of a text message, e-mail, cell phone message, page or other electronic communication.

11. A sensor, comprising:

an acoustic transmitter, driven by an excitation signal having an excitation frequency, that emits an acoustic interrogation signal having the excitation frequency into a fluid delivery medium in which presence or absence of a fluid is to be determined;

an acoustic detector that generates an acoustic signal output having the excitation frequency based on detection of the acoustic interrogation signal transmitted through the fluid delivery medium; and

a controller that calculates a phase shift between the acoustic signal output and the excitation signal, compares the phase shift with at least one predetermined threshold criteria and determines presence or absence of the fluid within the fluid delivery medium based on the phase shift.

12. The sensor of claim 11, wherein the controller further includes a transmitter module that controls generation of the excitation signal.

13. The sensor of claim 11, wherein the controller further includes a detection module that multiplies the excitation signal and the acoustic signal output to obtain a DC output signal indicative of the phase shift between the acoustic signal output and the excitation signal.

14. The sensor of claim 11, wherein the controller compares the phase shift to a predetermined lower threshold and a predetermined upper threshold.

15. The sensor of claim 12, wherein the controller detects an out-of-product event when the phase shift is between the predetermined lower threshold and the predetermined upper threshold.

16. The sensor of claim 11, wherein the controller further generates an out-of-product alert when absence of fluid in the fluid delivery medium is determined.

17. The sensor of claim 16, wherein the out-of-product alert is at least one of a message to an external device, a visible indicator, or an audible indicator.

18. The sensor of claim 11, wherein the excitation frequency is between about 5 kilohertz and 40 kilohertz.

19. The sensor of claim 11, wherein the excitation frequency is chosen such that a wavelength in air of the excitation signal is between 0.3 and 1 times the diameter of the fluid delivery medium.

20. The sensor of claim 19, wherein the excitation frequency is chosen such that one half of the wavelength in air of the excitation signal is approximately equal to the diameter of the fluid delivery tubing.

21. A computer readable medium comprising instructions that cause a programmable processor to:

generate an excitation signal that excites emission of an acoustic interrogation signal into a fluid delivery medium in which presence or absence of a fluid is to be determined;

receive the acoustic interrogation signal transmitted through the fluid delivery medium and generate therefrom an acoustic signal output;

determine a phase shift between the acoustic signal output and the excitation signal; and

determine presence or absence of the fluid within the fluid delivery medium based on the phase shift.

22. The method of claim 21, further comprising comparing the phase shift with at least one predetermined threshold criteria.

23. The method of claim 22, further comprising detecting an out-of-product event when the at least one predetermined threshold criteria is satisfied.

24. The method of claim 21, wherein determining the phase shift comprises multiplying the excitation signal and the acoustic signal output and obtaining therefrom a DC output signal indicative of the phase shift between the acoustic signal output and the excitation signal

25. The method of claim 21, further comprising generating an out-of-product alert when absence of fluid in the fluid delivery medium is determined.