System for monitoring fluent material within a container

• US 4,811,595 A
• Filed: 04/06/1987
• Issued: 03/14/1989
• Est. Priority Date: 04/06/1987
• Status: Expired due to Fees

• Current Assignee: Applied Acoustic Research
• Original Assignee: Applied Acoustic Research
• Inventors: Poole, Lynn A., Marciniak, Robert D.
• Primary Examiner(s): Noland, Tom
• Application Number:
  US07/035,003
• Time in Patent Office: 708 Days
• Field of Search: 73/149, 73/290 B, 73/290 V
• US Class Current: 73/149
• CPC Class Codes: G01F 22/02 involving measurement of pressure
• CPC Class Codes: G01F 23/2966 making use of acoustical resonance or standing waves

Abstract

The acoustical energy output of a source is varied in frequency between limits to sweep a frequency band encompassing cavity resonance conditions which depend on the quantity of a fluent material within a tank excited by such acoustical energy. The volume of the fluent material is calculated from the excitation frequency registered during verified detection of resonance conditions, based on abrupt changes in signal characteristics and stored data relating to the geometry of the acoustic sensor arrangement through which the tank interior is monitored.

Claims

1. In a method of monitoring an unknown volume of a fluent material within a container by directing acoustical energy at an excitation frequency into the container and sensing acoustical vibrations emitted therefrom having phase and amplitude characteristics, the improvement comprising the steps of:

varying the excitation frequency to sweep a frequency band between limits respectively corresponding to cavity resonance conditions of the container when full and empty;

measuring at least one of the characteristics of the acoustical vibrations during said variation in the excitation frequency;

detecting abrupt changes in said one of the measured characteristics of the acoustical vibrations;

registering the excitation frequency during said detection of the abrupt changes in the measured characteristic; and

calculating the unknown volume of the fluent material from said registered excitation frequency corresponding to cavity resonance conditions of the container between said limits of the frequency band.

2. In the method of claim 1 wherein the container includes a resonator cavity within which the fluent material is confined and a throat passage through which the acoustical energy enters into the cavity.

3. The method of claim 1 wherein said one of the measured characteristics is phase angle.

4. The method of claim 1 wherein said one of the measured characteristics is amplitude and the abrupt changes detected are maxima peaks.

5. The method of claim 1 including the steps of:

measuring another of the characteristics of the sensed vibrations during said variation in the excitation frequency; and

detecting the maximum value of said other of the characteristics, said frequency registering step being limited to an interval during which detection of the maximum value of said other of the characteristics is detected.

6. The method of claim 1 including the steps of:

differentiating the calculated volume of the fluent material with respect to time to determine flow rate of the fluent material with respect to the container.

7. A system for monitoring the quantity of a fluent material within a container, including a source of acoustical energy externally of the container, means for directing the acoustical energy from said source into the container, said acoustical energy varying in excitation frequency between frequency limits respectively established under cavity resonance conditions in the container when empty and full of the fluent material, means operatively mounted on the container for sensing acoustical vibrations emitted therefrom during said variation of the excitation frequency, means operatively connected to the sensing means for detecting abrupt changes in at least one of the signal characteristics of the sensed acoustical vibrations, data storage means connected to the detecting means for registering the excitation frequency of the acoustical energy during said detection of the abrupt changes corresponding to cavity resonance conditions in the container and data processing means connected to the storage means for calculating volume of said fluent material as a function of the registered excitation frequency and said frequency limits.

8. The combination of claim 7 wherein the signal characteristic of the sensed acoustical vibration is phase angle.

9. The combination of claim 8 including additional means for detecting an abrupt change in another of the signal characteristics of the sensed acoustical vibrations and means for rendering the detecting means operative to register the excitation frequency within an interval during which said detection by the additional detecting means occurs.

10. The combination of claim 7 wherein said container includes a resonator cavity within which the fluent material is confined and a throat passage portion through which the acoustical energy is directed into the cavity at the excitation frequency, and auxiliary cavity means connected in spaced relation to the resonator cavity by the throat passage portion for mounting the source of acoustical energy and the sensing means.

11. The improvement as defined in claim 7 wherein said source of acoustical energy is a speaker device and sweep control means connected to the data processing means for driving the speaker device at the varying excitation frequency.

12. The combination of claim 7 wherein said source of acoustical energy is of environmental origin.

13. The combination of claim 7 wherein said source of acoustical energy and the sensing means are formed by a common transducer device alternatively operated in transmit and receive operational modes and mode control means operatively connected to the data processing means for cyclically switching operation of the transducer device between said operational modes thereof.

14. In a system for monitoring the quantity of a fluent material, including a source of acoustical energy varying in excitation frequency, resonance cavity means into which said acoustical energy is directed for producing acoustical vibrations at a resonance value of the excitation frequency dependent on the quantity of the fluent material therein and sensing means for producing signals in response to said acoustical vibrations, the improvement residing in said resonance cavity means including separate interrelated chambers within which the fluent material is retained and the sensing means is located, respectively, means directing the acoustical energy into at least one of the chambers without interference for inducing the acoustical vibrations at said excitation frequency varying between limits respectively established by resonance conditions within said one of the chambers when empty and full of the fluent material retained therein, resonance detecting means connected to the sensing means for registering said resonant value of the excitation frequency during an abrupt change in characteristic of the signal produced in response to the acoustical vibrations being sensed and data processing means connected to the resonance detecting means for calculating the quantity of the fluent material as a function of the registered resonant value of the excitation frequency and the established limits thereof.

15. The system as defined in claim 14 including resonance verification means for detecting an abrupt change in another characteristic of the signal produced by the acoustical vibrations being sensed during said registration of the resonant value of the excitation frequency.

16. The system as defined in claim 15 wherein the other of the chambers forms an unobstructed passage between the acoustical energy source and said one of the chambers within which the fluent material is retained.

17. The system as defined in claim 14 wherein the other of the chambers forms an unobstructed passage between the acoustical energy source and said one of the chambers within which the fluent material is retained.

18. The system as defined in claim 14 wherein the other of the chambers is a resonance cavity within which the sensing means is located and passage means interconnecting said chambers.