Ultrasonic detector

• US 5,191,795 A
• Filed: 08/23/1991
• Issued: 03/09/1993
• Est. Priority Date: 05/01/1987
• Status: Expired due to Term

• Current Assignee: Hospira Incorporated (Pfizer Inc.)
• Original Assignee: Abbott Laboratories
• Inventors: Koll, Lance B., Hughes, Timothy J., Fellingham, George H.
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US07/753,009
• Time in Patent Office: 564 Days
• Field of Search: 73/599, 73/642, 73/19.1, 73/19.03, 310/316, 340/621, 367/903
• US Class Current: 73/599
• CPC Class Codes: A61M 5/365 Air detectors A61M5/1684 takes precedence; in extracorporeal blood circuits A61M1/3626
• CPC Class Codes: G01N 2291/02433 Gases in liquids, e.g. bubbles, foams
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/24 Probes transducers for acoustic waves B06B, G10K; for measuring G01H
• CPC Class Codes: G01N 29/28 providing acoustic coupling , e.g. water impedance matching G10K11/02
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14

Abstract

An ultrasonic detector for detecting air in a fluid passage is disclosed. The detector comprises a transmitting crystal and complementary receiving crystal disposed around the fluid passage. A sweep oscillator is used to apply a variable-frequency signal to drive the transmitting crystal into resonance so that a burst of ultrasonic energy is released therefrom. The swept frequency range encompasses the resonant frequency of the transmitting crystal, ensuring that it resonates. If there is fluid in the passage, the ultrasonic energy causes a relatively high voltage to develop across the receiving crystal. Air in the passage attenuates transmission of the ultrasonic energy so that a low voltage signal is developed across the receiving crystal. A sensor circuit connected to the receiving crystal monitors the signal developed thereacross and in response to the magnitude of the signal, asserts a signal that indicates whether there is air or fluid in the passage.

Claims

1. A device for detecting the presence of liquid-state fluid in a conduit, comprising:

(a) acoustic transmitter means for generating acoustic signals across the conduit, said acoustic transmitter means generating said acoustic signals in response to a drive signal at a selected frequency applied thereto;

(b) signal generating means for applying a drive signal to said acoustic transmitter means, said signal generator means continuously generating said drive signal over a sweep range of frequencies including said acoustic transmitter drive signal selected frequency so as to cause said acoustic transmitter means to periodically emit said acoustic signals; and

(c) acoustic receiver means responsive to said acoustic signals emitted by said acoustic transmitter means, for producing a signal indicative of whether or not liquid-state fluid is present in the conduit wherein said signals indicative of the presence of liquid-state fluid is periodically produced when said acoustic signals are received.

2. The device for detecting the presence of fluid of claim 1, wherein said signal generating means comprises a sweep oscillator generating an output signal over said sweep range of frequencies, and an amplifier coupled to said sweep oscillator so as to receive said output signals, and in response thereto, producing said signal generator drive signal.

3. The device for detecting the presence of fluid of claim 2, wherein said sweep oscillator includes a voltage controlled oscillator, and a triangle wave oscillator that applies a varying voltage signal to said voltage controlled oscillator, whereby said variable voltage signal causes said voltage controlled oscillator to generate said sweep oscillator output signal.

4. The device for detecting the presence of fluid of claim 2, wherein said sweep oscillator selectively generates said sweep frequency range output signal, and said amplifier includes a switch responsive to said oscillator output signal, for allowing current flow through said amplifier only when said swept frequency range output signal is generated.

5. The device for detecting the presence of fluid of claim 4, wherein:

(a) said sweep oscillator generates said sweep frequency range output signal in response to an oscillator-on signal;

(b) said acoustic receiver means generates a fluid-in-line signal whenever said acoustic signal is emitted from said acoustic transmitter means and there is at least a selected amount of liquid in the conduit; and

(c) further including processor means connected to said sweep oscillator for periodically transmitting said oscillator-on signal thereto, and connected said acoustic receiver means for receiving said fluid-in-line signal, and operative when said oscillator-on signal is transmitted and said fluid-in-line signal is not received, to transmit an alarm signal so as to cause actuation of an alarm.

6. The device for detecting the presence of fluid of claim 5, wherein said test is performed by said processor means at selected times after said process means has completed transmitting said oscillator-on signal and after said fluid-in-line signal has been transmitted.

7. The device for detecting the presence of fluid of claim 4, wherein:

said sweep oscillator selectively generates said sweep frequency range output signal in response to a signal generator-on signal;

said acoustic transmitter means periodically generates said acoustic signals when said amplifier produces said signal generator drive signal at said acoustic transmitter drive signal frequency;

said acoustic receiver means generates a fluid-in-line signal after a selected number of said acoustic signals are emitted and there is a selected amount of liquid in the conduit; and

further including processor means connected to said signal generator means for periodically transmitting said signal generator-on signal thereto, and connected to said acoustic receiver means for receiving said fluid-in-line signal, and operative at a selected time when said generator-on signal is transmitted and said fluid-in-line signal is not received, to generate an alarm signal so as to actuate an alarm.

8. The device for detecting the presence of fluid of claim 1, wherein:

(a) said acoustic transmitter means includes a first transmitter that is responsive to acoustic transmitter drive signals at a first selected frequency, and a second transmitter that is responsive to acoustic transmitter drive signals at a second selected frequency, said first and second selected frequencies being different;

(b) said receiver means includes a plurality of acoustic receivers, each being responsive to acoustic signals emitted by one of said plurality of acoustic transmitters; and

(c) said signal generator means is operative to apply said drive signal to each of said acoustic transmitters and operative to generate said drive signal over said sweep range of frequencies, said sweep range of frequencies including said acoustic transmitter drive signals at said first and second selected frequencies.

9. The device for detecting the presence of fluid of claim 8, wherein said signal generator means comprises a sweep oscillator generating an output signal over said swept range of frequencies, and signal amplifier means coupled to said sweep oscillator so as to receive said output signals therefrom and in response thereto, generating said signal generator drive signal.

10. The device for detecting the presence of fluid of claim 9, further including separate attenuation means attached between said amplifier means and each of said acoustic transmitters for controlling the magnitude of said drive signal applied to said acoustic transmitter.

11. The device for detecting the presence of fluid of claim 1, wherein:

(a) said signal generation means selectively generates said drive signal in response to a signal generator-on signal;

(b) said acoustic receiver means generates a fluid-in-line signal when said acoustic signal is emitted and there is a selected amount of liquid in the conduit; and

(c) further including processor means connected to said signal generator means and periodically transmitting said signal generator-on signal thereto, and connected to said acoustic receiver means for receiving said fluid-in-line signal, and operative when said generator-on signal is transmitted and said fluid-in-line signal is not received, to transmit an alarm signal to cause actuation of an alarm.

12. The device for detecting the presence of fluid of claim 11, wherein said processor means is further operative to test said acoustic transmitter means, said generator means, and said acoustic receiver means by selectively monitoring signals from said acoustic receiver means when said signal generator-on signal is not transmitted, and if said fluid-in-line signal is then received, to transmit an alarm signal so as to cause actuation of an alarm.

13. The device of detecting the presence of fluid of claim 12, wherein said test is preformed by said processor means at a selected time after said processor means stops transmitting said signal generator-on signal, and after said fluid-in-line signal has been transmitted.

14. The device for detecting the presence of fluid of claim 13, wherein said processor means is operative to test said acoustic transmitter means, said sweep signal generating means, and said acoustic receiver means by selectively monitoring signals from said acoustic receiver means when said oscillator-on signal is not transmitted, and if said fluid-in-line signal is then received, to transmit an alarm signal so as to cause actuation of an alarm.

15. The device for detecting fluid of claim 1, wherein said acoustic receiving means comprises:

(a) a receiver transducer for receiving said acoustic signals and generating a receiver transducer signal in response to the magnitude of said received acoustic signals;

(b) amplifier means coupled to said receiver transducer, for generating an output signal proportional to said receiver transducer signal; and

(c) AM detector means coupled to said amplifier means, for receiving said amplifier output signal therefrom, and in response thereto producing a detector signal having a voltage proportional to the magnitude of said amplifier output signal.

16. The device for detecting fluid of claim 15, wherein said amplifier output signal is applied to said AM detector through an AC coupling capacitor.

17. The device for detecting fluid of claim 15, further including a comparator for receiving said AM detector signal and comparing it to a reference voltage, said comparator transmitting a fluid-in-line signal in response to the difference between said detector signal voltage and said reference voltage.

18. The device for detecting fluid of claim 15, wherein said AM detector means includes a slow-discharge peak follower circuit.

19. The device for detecting the presence of fluid of claim 1, wherein said signal generator means comprises:

a sweep oscillator generating an output signal over said sweep range of frequencies, said sweep oscillator generating said signal in response to a signal generator-on signal produced by a detector control circuit; and

an amplifier including at least one amplifying element connected to a power source, for producing said acoustic transmitter drive signals and a switch connected to said amplifying element for selectively controlling current flow through said amplifying element and connected to said sweep oscillator for receiving said oscillator output signal, said switch being responsive to said oscillator output signal, whereby, when said oscillator output signal is not produced, the switch interrupts current flow through said amplifying element.

20. The device for detecting the presence of fluid of claim 19, wherein said amplifier includes a tank circuit connected to the power supply and a field-effect transistor connected to said tank circuit to control current flow therethrough, said field-effect transistor being further connected to said sweep oscillator for receiving said oscillator output signal so that said oscillator output signal gates said field-effect transistor.

21. The device for detecting the presence of fluid of claim 20 wherein said field effect transistor is connected between said tank circuit and ground.

22. An ultrasonic detector for monitoring the presence of liquid-state fluid in a conduit, comprising:

(a) an acoustic transmitter for generating acoustic signals across the conduit, said acoustic transmitter generating said acoustic signals in response to a drive signal at a selected frequency applied thereto;

(b) an acoustic receiver responsive to said acoustic signals generated by said acoustic transmitter for producing a signal indicative of whether or not liquid-state fluid is present in the conduit, wherein said signal indicative of the presence of liquid-state fluid is periodically produced when said acoustic signals are received; and

(c) a signal generator for applying a drive signal to said acoustic transmitter including a sweep oscillator for continuously generating an output signal over a swept range of frequencies including said acoustic transducer selected frequency and an amplifier coupled to said sweep oscillator for receiving said oscillator output signals and, in response thereto, producing said drive signal for application to said acoustic transducer signal so as to cause said acoustic transmitter to periodically emit said acoustic signals, wherein said amplifier includes an amplifying element connected to a power supply and a switch for selectively controlling current flow through said amplifying element, said switch being responsive to said oscillator output signal, whereby, when said oscillator output signal is not produced, the switch interrupts current flow through said amplifying element.

23. The ultrasonic detector of claim 22, wherein said amplifying element is a tank circuit.

24. The ultrasonic detector of claim 23, wherein said switch is a field-effect transistor connected to said sweep oscillator so that said sweep oscillator gates said transistor and connected between said tank circuit and ground to selectively connect said tank circuit to ground in response to receipt of said oscillator output signal.

25. The ultrasonic detector of claim 22, wherein said switch is a field-effect transistor connected to said sweep oscillator so that said sweep oscillator gates said transistor and connected between said amplifying element and ground to selectively connect said amplifying element to ground in response to receipt of said oscillator output signal.

26. An ultrasonic detector for monitoring the presence of liquid-state fluid in a conduit, comprising:

(a) at least two spaced-apart acoustic transmitters for generating acoustic signals across the conduit, including a first acoustic transmitter that generates acoustic signals in response to a first drive signal at a first selected frequency and a second acoustic transmitter that generates acoustic signals in response to a second drive signal at a second selected frequency, wherein said first and second selected frequencies are different;

(b) a plurality of acoustic receivers, each of said receivers being responsive to said acoustic signals generated by a separate one of said acoustic transmitters for producing signals indicative of whether or not liquid-state fluid is present in the conduit, wherein each of said acoustic receivers produces a signal indicative of the presence of liquid-state fluid when said acoustic signals are received; and

(c) a signal generator for applying a drive signal to said acoustic transmitters including a sweep oscillator for continuously generating an output signal over a swept range of frequencies including said first and second selected frequencies and an amplifier coupled to said sweep oscillator for receiving said oscillator output signal and, in response thereto, producing said drive signal for application to said acoustic transducers so as to cause each said acoustic transmitter to periodically emit said acoustic signals.

27. The ultrasonic detector of claim 26, wherein said amplifier includes at least one amplifying element connected to a power source for producing said acoustic transmitter drive signal and a switch connected to said amplifying element for selectively controlling current flow through said amplifying element and connected to said sweep oscillator for receiving said oscillator output signal, said switch being responsive to said oscillator output signal, whereby, when said oscillator output signal is not produced, the switch interrupts current flow through said amplifying element.

28. The ultrasonic detector of claim 27, wherein said amplifier includes a tank circuit connected to the power supply and a field-effect transistor connected to said tank circuit to control current flow therethrough, said field-effect transistor further connected to said sweep oscillator for receiving said oscillator output signal so that said oscillator output signal gates said field-effect transistor. el