Ultrasonic liquid flow controller

• US 20050288873A1
• Filed: 06/28/2004
• Published: 12/29/2005
• Est. Priority Date: 06/28/2004
• Status: Active Grant

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Celerity Incorporated (ICHOR Holdings, Ltd.)
• Inventors: Redemann, Eric J., Tint, Aaron S., Duan, Hao, Wacinski, Christopher Andrew, Urdaneta, Nelson
• Granted Patent: US 7,117,104 B2
• Time in Patent Office: Days
• US Class Current: 137/487.5
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

An ultrasonic flow meter includes a conduit, a first ultrasonic transducer, a second ultrasonic transducer, and a controller. The first ultrasonic transducer is disposed at a first position about a first portion of the conduit to transmit a first ultrasonic signal and to receive a second ultrasonic signal. The second ultrasonic transducer is disposed at a second position about a second portion of the conduit that is spaced apart from the first position along a length of the conduit to transmit the second ultrasonic signal and to receive the first ultrasonic signal. The controller is configured to cross-correlate the first and second received ultrasonic signals and generate a resulting time-domain signal, analyze the resulting time-domain signal to determine a difference in transit time between the first and second received ultrasonic signals, and calculate a rate of flow of a fluid in the conduit based upon the determined difference.

Claims

1. A method of determining a rate of flow of a fluid in a conduit, the method comprising acts of:

sending first and second ultrasonic signals along a length of the conduit;

receiving the first and second ultrasonic signals;

cross-correlating the first received ultrasonic signal and the second received ultrasonic signal to generate a resulting time-domain signal;

analyzing the resulting time-domain signal to determine a difference in transit time between the first received ultrasonic signal and the second received ultrasonic signal; and

calculating the rate of flow of the fluid in the conduit based upon the determined difference.

2. The method as claimed in claim 1, wherein the act of cross-correlating comprises:

performing a Fourier transform on the first received ultrasonic signal to generate a first frequency-domain representation;

performing a Hilbert transform and a Fourier transform on the second received ultrasonic signal to generate a second frequency-domain representation;

multiplying the first and second frequency-domain representations together to generate a resulting frequency-domain representation; and

performing an inverse Fourier transform on the resulting frequency-domain representation to generate the resulting time-domain signal.

3. The method as claimed in claim 2, wherein the act of analyzing the resulting time-domain signal comprises locating a zero crossing within the resulting time-domain signal.

4. The method as claimed in claim 3, further comprising an act of setting DC and Nyquist-rate terms of the resulting frequency-domain representation to zero prior to the act of performing the inverse Fourier transform on the resulting frequency-domain representation.

5. The method as claimed in claim 1, further comprising an act of determining a speed of propagation of at least one of the first and second ultrasonic signals in the fluid.

6. The method as claimed in claim 5, wherein the act of calculating the rate of flow of the fluid based upon the determined difference is performed more frequently than the act of determining the speed of propagation.

7. The method as claimed in claim 5, wherein the act of determining the speed of propagation comprises:

determining a first transit time of the first ultrasonic signal between first and second positions that are spaced apart along the length of the conduit;

determining a second transit time of the second ultrasonic signal between the second and first positions; and

calculating the speed of propagation based upon the first and second transit times and a distance between the first and second positions.

8. The method as claimed in claim 7, further comprising an act of periodically updating the speed of propagation of the at least one ultrasonic signal in the fluid by periodically repeating the acts of determining the first and second transit times and the act of calculating the speed of propagation.

9. The method as claimed in claim 8, wherein the act of calculating the rate of flow of the fluid includes an act of calculating the rate of flow based upon the determined difference and the speed of propagation.

10. The method as claimed in claim 1, wherein the act of cross-correlating comprises:

performing a Fourier transform on each of the first received ultrasonic signal and the second received ultrasonic signal to generate a first frequency-domain representation and a second frequency-domain representation, respectively;

multiplying the first and second frequency-domain representations together to generate a resulting frequency-domain representation; and

performing an inverse Fourier transform on the resulting frequency-domain representation to generate the resulting time-domain signal.

11. The method as claimed in claim 10, further comprising acts of:

adding one of a positive 90 degree phase shift and a negative 90 degree phase shift to each positive frequency component of one of the first frequency-domain representation and the second frequency-domain representation; and

adding the other of a positive 90 degree phase shift and a negative 90 degree phase shift to each negative frequency component of the one of the first frequency-domain representation and the second frequency-domain representation.

12. The method as claimed in claim 1, wherein the act of sending the first and second ultrasonic signals includes an act of digitally synthesizing the first and second ultrasonic signals from a digital representation of a chirp signal.

13. An ultrasonic flow meter comprising:

a conduit;

a first ultrasonic transducer, disposed at a first position along a length of the conduit, to transmit a first ultrasonic signal and to receive a second ultrasonic signal;

a second ultrasonic transducer, disposed at a second position along the length of the conduit that is spaced apart from the first position, to transmit the second ultrasonic signal and to receive the first ultrasonic signal; and

a controller configured to cross-correlate the first received ultrasonic signal and the second received ultrasonic signal and generate a resulting time-domain signal, to analyze the resulting time-domain signal to determine a difference in transit time between the first received ultrasonic signal and the second received ultrasonic signal, and to calculate a rate of flow of a fluid in the conduit based upon the determined difference.

14. The ultrasonic flow meter as claimed in claim 13, wherein the controller is further configured to:

perform a Fourier transform on the first received ultrasonic signal to generate a first frequency-domain representation;

perform a Hilbert transform and a Fourier transform on the second received ultrasonic signal to generate a second frequency-domain representation;

multiply the first and second frequency-domain representations together to generate a resulting frequency-domain representation; and

perform an inverse Fourier transform on the resulting frequency-domain representation to generate the resulting time-domain signal.

15. The ultrasonic flow meter as claimed in claim 14, wherein the controller is further configured to analyze the resulting time-domain signal by locating a zero crossing within the resulting time-domain signal.

16. The ultrasonic flow meter as claimed in claim 15, wherein the controller is further configured to set DC and Nyquist-rate terms of the resulting frequency-domain representation to zero prior to performing the inverse Fourier transform on the resulting frequency-domain representation.

17. The ultrasonic flow meter as claimed in claim 15, wherein the controller is further configured to determine a speed of propagation of the first and second ultrasonic signals in the fluid by determining a first transit time of the first ultrasonic signal between first and second positions, determining a second transit time of the second ultrasonic signal between the second and first positions, and calculating the speed of propagation based upon the first and second transit times and a distance between the first and second positions along the length of the conduit.

18. The ultrasonic flow meter as claimed in claim 17, wherein the controller is configured to calculate the rate of flow of the fluid based upon the determined difference and the speed of propagation.

19. The ultrasonic flow meter as claimed in claim 18, further comprising:

a timing circuit, operatively coupled to the first and second ultrasonic transducers, to initiate transmission of the first and second ultrasonic signals after a determined delay relative to a reference event.

20. The ultrasonic flow meter as claimed in claim 19, further comprising:

a transmitter circuit, responsive to the timing circuit and switchably connected to each of the first and second ultrasonic transducers, to generate the first and second ultrasonic signals and to provide the first and second ultrasonic signals to the first and second ultrasonic transducers for transmission.

21. The ultrasonic flow meter as claimed in claim 20, further comprising:

a receiver circuit, switchably connected to each of the first and second ultrasonic transducers, to receive the first and second ultrasonic signals and to provide the first and second received ultrasonic signals to the controller.

22. The ultrasonic flow meter as claimed in claim 21, wherein the transmitter circuit includes:

a storage circuit to store digital representations of the first ultrasonic signal and the second ultrasonic signal;

a digital to analog converter, electrically coupled to the storage circuit, to convert the digital representations of the first ultrasonic signal and the second ultrasonic signal to analog representations;

a filter, electrically coupled to the digital to analog converter, to filter the analog representations; and

an amplifier, electrically coupled to the filter, to amplify the filtered analog representations and to provide the filtered analog representations to the first and second ultrasonic transducers for transmission.

23. The ultrasonic flow meter as claimed in claim 22, wherein each of the first and second ultrasonic signals includes an ultrasonic chirp signal.

24. The ultrasonic flow meter as claimed in claim 17, wherein the controller is configured to calculate the rate of flow of the fluid based upon the determined difference, the speed of propagation, and a cross-sectional area of the conduit.

25. The ultrasonic flow meter as claimed in claim 17, wherein the controller is configured to calculate the rate of flow of the fluid based upon the determined difference, the speed of propagation, a cross-sectional area of the conduit, and a specific density of the fluid in the conduit.

26. The ultrasonic flow meter as claimed in claim 13, further comprising:

a timing circuit, operatively coupled to the first and second ultrasonic transducers, to initiate transmission of the first and second ultrasonic signals after a first determined delay relative to a reference event.

27. The ultrasonic flow meter as claimed in claim 26, wherein the timing circuit initiates reception of the first and second ultrasonic signals after a second determined delay relative to the reference event.

28. The ultrasonic flow meter as claimed in claim 13, further comprising:

a transmitter circuit to generate the first and second ultrasonic signals and to provide the first and second ultrasonic signals to the first and second ultrasonic transducers for transmission.

29. The ultrasonic flow meter as claimed in claim 28, further comprising:

a receiver circuit to receive the first and second ultrasonic signals and to provide the first and second received ultrasonic signals to the controller.

30. The ultrasonic flow meter as claimed in claim 28, wherein the transmitter circuit includes:

a storage circuit to store digital representations of the first ultrasonic signal and the second ultrasonic signal;

a digital to analog converter, electrically coupled to the storage circuit, to convert the digital representations of the first ultrasonic signal and the second ultrasonic signal to analog representations; and

an amplifier, electrically coupled to the digital to analog converter, to amplify the analog representations and to provide the analog representations to the first and second ultrasonic transducers for transmission.

31. The ultrasonic flow meter as claimed in claim 13, wherein each of the first and second ultrasonic signals includes an ultrasonic chirp signal.

32. The ultrasonic flow meter as claimed in claim 31, wherein the ultrasonic chirp signal is digitally synthesized.

33. An ultrasonic flow meter comprising:

a conduit;

a first ultrasonic transducer, disposed at a first position along a length of the conduit, to transmit a first ultrasonic signal and to receive a second ultrasonic signal;

a second ultrasonic transducer, disposed at a second position along the length of the conduit that is spaced apart from the first position, to transmit the second ultrasonic signal and to receive the first ultrasonic signal;

a timing circuit, operatively coupled to the first and second ultrasonic transducers, to initiate transmission of the first and second ultrasonic signals after a determined delay relative to a reference event; and

a controller to process the first and second received ultrasonic signals and determine a difference in time between receipt of the first received ultrasonic signal and receipt of the second received ultrasonic signal relative to the reference event.

34. The ultrasonic flow meter of claim 33, wherein the determined delay is the same for the first and second ultrasonic signals.

35. The ultrasonic flow meter of claim 33, further comprising:

a transmitter circuit, responsive to the timing circuit and switchably connected to each of the first and second ultrasonic transducers, to generate the first and second ultrasonic signals and provide the first and second ultrasonic signals to the first and second ultrasonic transducers for transmission.

36. The ultrasonic flow meter of claim 35, further comprising:

a receiver circuit, switchably connected to each of the first and second ultrasonic transducers, to receive the first and second ultrasonic signals and provide the first and second received ultrasonic signals to the controller.

37. The ultrasonic flow meter of claim 35, wherein the transmitter circuit includes:

a storage circuit to store digital representations of the first ultrasonic signal and the second ultrasonic signal; and

a digital to analog converter, electrically coupled to the storage circuit, to convert the digital representations of the first ultrasonic signal and the second ultrasonic signal to analog representations.

38. The ultrasonic flow meter of claim 37, wherein the digital representation of the first ultrasonic signal is the same as the digital representation of the second ultrasonic signal.

39. The ultrasonic flow meter of claim 37, wherein the transmitter circuit further includes:

a filter, electrically coupled to the digital to analog converter, to filter the analog representations; and

an amplifier, electrically coupled to the filter, to amplify the filtered analog representations and to provide the filtered analog representations to the first and second ultrasonic transducers for transmission.

40. The ultrasonic flow meter of claim 39, wherein the digital representations of the first ultrasonic signal and the second ultrasonic signal correspond to a chirp signal.

41. The ultrasonic flow meter of claim 33, further comprising:

a receiver circuit, switchably connected to each of the first and second ultrasonic transducers, to receive the first and second ultrasonic signals and provide the first and second received ultrasonic signals to the controller.

42. The ultrasonic flow meter of claim 33, wherein each of the first and second ultrasonic signals includes an ultrasonic chirp signal.

43. The ultrasonic flow meter of claim 33, wherein upon receipt of the first and second received ultrasonic signals, the controller performs a cross-correlation between the first and second received ultrasonic signals to determine the difference in time between receipt of the first received ultrasonic signal and receipt of the second received ultrasonic signal relative to the reference event.

44. A method of determining a rate of flow of a fluid in a conduit, the method comprising acts of:

(a) transmitting a first ultrasonic signal from a first position disposed along a length of the conduit;

(b) transmitting a second ultrasonic signal from a second position disposed along the length of the conduit, the second position being spaced apart along the length of the conduit from the first position by a distance;

(c) receiving the first ultrasonic signal at the second position;

(d) receiving the second ultrasonic signal at the first position;

(e) determining a speed of propagation of at least one of the first and second ultrasonic signals in the fluid;

(f) processing only the received first and second ultrasonic signals to determine a difference in time between receipt of the first ultrasonic signal and receipt of the second ultrasonic signal; and

(g) calculating the rate of flow of the fluid based upon the speed of propagation determined in act (e) and the difference in time between the receipt of the first ultrasonic signal and the receipt of the second ultrasonic signal determined in act (f).

45. The method of claim 44, wherein the act (e) comprises:

determining a first transit time of the first ultrasonic signal between the first and second positions;

determining a second transit time of the second ultrasonic signal between the second and first positions;

calculating the speed of propagation of at least one of the first and second ultrasonic signals in the fluid based upon the first and second transit times and the distance between the first and second positions.

46. The method of claim 45, further comprising acts of:

measuring a temperature of the fluid in the conduit; and

adjusting a value of the distance between the first and second positions based upon the temperature of the fluid in the conduit.

47. The method of claim 44, further comprising acts of:

repeating, at a first rate of repetition, the acts (f) and (g); and

periodically updating the speed of propagation determined in act (e) at a second rate of repetition that is slower than the first rate of repetition.

48. The method of claim 44, further comprising acts of:

repeating, at a first rate of repetition, the acts (f) and (g);

determining whether a temperature of the fluid in the conduit has changed subsequent to the act (e); and

updating the speed of propagation determined in act (e) in response to a determination that the temperature of the fluid in the conduit has changed.

49. The method of claim 44, wherein the act (g) includes an act of calculating the rate of flow of the fluid based upon the speed of propagation determined in act (e), the difference in time between the receipt of the first ultrasonic signal and the receipt of the second ultrasonic signal determined in act (f), and a cross-sectional area of the conduit.

50. The method of claim 49, further comprising acts of:

measuring a temperature of the fluid in the conduit; and

adjusting the cross-sectional area of the conduit based upon the temperature of the fluid in the conduit.

51. The method of claim 44, the act (g) includes an act of calculating the rate of flow of the fluid based upon the speed of propagation determined in act (e), the difference in time between the receipt of the first ultrasonic signal and the receipt of the second ultrasonic signal determined in act (f), a cross-sectional area of the conduit, and a specific density of the fluid in the conduit.

52. The method of claim 51, further comprising acts of:

measuring a temperature of the fluid in the conduit;

adjusting the cross-sectional area of the conduit based upon the temperature of the fluid in the conduit; and

adjusting the specific density of the fluid based upon the temperature of the fluid in the conduit.