Volume measurement system

• US 4,561,298 A
• Filed: 06/29/1984
• Issued: 12/31/1985
• Est. Priority Date: 07/01/1983
• Status: Expired due to Fees

• Current Assignee: John B. Pond
• Original Assignee: John B. Pond
• Inventors: Pond, John B.
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US06/626,063
• Time in Patent Office: 550 Days
• Field of Search: 73/149, 73/290 B, 73/290 V
• US Class Current: 73/149
• CPC Class Codes: G01F 17/00 Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies measuring linear dimensions to determine volume G01B

Abstract

A method of, and apparatus for, measuring the free volume of a confined space or container is described. The method comprises applying to the gas or vapor within the confined space or container repeated compressions of predetermined waveform by means of a barrier or diaphragm; generating electrical signals representative of the resultant variation of pressure within the confined space or container; repeatedly sampling said electrical signals at regular predetermined instants, or over regular predetermined time ranges, corresponding to predetermined points or regions of said waveform; combining or integrating the sampled signals to generate thereby a time-averaged output signal; and calculating the free volume of the confined space or container from the output signal thus obtained. In one embodiment, the apparatus comprises (1) diaphragm means, for applying repeated compressions to said confined space or container; (2) drive means for moving said diaphragm means in accordance with a predetermined waveform; (3) a pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured; (4) electrical circuit means connected to said pressure-sensitive transducer and to said drive means, for sampling the electrical output of said pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged output signal from the signals generated by said electrical circuit means; and (5) means for determining from said time-averaged output signal a value representative of the free volume being measured.

Claims

1. A method of measuring the free volume within a confined space, which comprises applying to the gas within the confined space repeated compressions of predetermined waveform by means of an electrically driven diaphragm one face of which is coupled to said free volume and the other face of which is coupled to a second, known volume;

generating first electrical signals representative of the resultant variation of pressure within the confined space;

repeatedly sampling said first electrical signals during moments of maximum diaphragm excursion;

integrating the sampled signals to generate thereby a time-averaged first output signal;

generating second electrical signals representative of the resultant pressure variation in said second, known volume;

averaging said second electrical signals to generate a second ouput signal; and

calculating the free volume of the confined space from the first and second output signals thus obtained.

2. A method according to claim 1, wherein a moving coil loudspeaker is used to apply said repeated compressions.

3. A method according to claim 1, wherein the electrical signals representative of pressure variations within the volume being measured are generated by a pickup transducer sensitive to low frequencies.

4. A method according to claim 3, wherein said pickup transducer is a microphone.

5. Apparatus for measuring the free volume within a confined space, which apparatus is portable in form and comprises (1) diaphragm means, for applying repeated compressions to said confined space;

(2) a chamber of known volume;

(3) a duct communicating with and acting as an extension of said chamber of known volume, and supporting within it said diagraphm means;

(4) at that end of said duct remote from said chamber of known volume, a coupling attachment for attachment to the volume which is to be measured;

(5) drive means for moving said diaphragm means in accordance with a predetermined waveform;

(6) a first pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured;

(7) a second pressure-sensitive transducer for measuring pressure changes within said chamber of known volume;

(8) electrical circuit means connected to said first pressure-sensitive transducer and to said drive means, for sampling the electrical output of said first pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged output signal from the signals generated by said first pressure-sensitive transducer; and

(9) means for determining from said time-averaged output signal and from the responses of said second pressure-sensitive transducer a value representative of the free volume being measured.

6. Apparatus as claimed in claim 5, wherein said electrical circuit means comprises a first averaging element which is connected to said transducer only during times of maximum diaphragm excursion in one direction, and a second averaging element which is connected to said transducer only during times of maximum diaphragm excursion in the opposite direction, together with means for determining the difference between the outputs of said first and said second averaging elements, said outputs representing, respectively, first and second averaged signals derived from the response of said free volume to said repeated compressions.

7. Apparatus as claimed in claim 6, wherein said electrical circuit means further comprises a logic element which is arranged to calculate a parameter indicative of said free volume, from the difference between said output signals derived from said first transducer and from the output signal derived from said second transducer.

10. Apparatus as claimed in claim 5, which further comprises a logic element and means for input of data to the logic element, the logic element being arranged to calculate from the determined value of the free volume and from data supplied via the data input means a parameter related to the free volume of the confined space.

11. Apparatus as claimed in claim 10, wherein said logic element is arranged to calculate the state of fill a container which, together with its contents define said confined space.

15. Apparatus as claimed in claim 5 wherein said drive means for moving said diaphragm means in accordance with a predetermined waveform is a square wave generator.

16. Apparatus as claimed in claim 5, which comprises a by-pass duct located as a by-pass around said diaphragm means;

a one-way valve located in said by-pass duct so as to admit gases or vapours from upstream of the diaphragm means into the chamber of known volume downstream of the diaphragm means; and

a pump for withdrawing gas or vapour from said chamber of known volume.

8. Apparatus for measuring the free volume within a confined space, which apparatus comprises (1) diaphragm means, for applying repeated compressions to said confined space or container;

(2) a chamber of known volume supporting said diaphragm means;

(3) drive means for moving said diaphragm means in accordance with a predetermined waveform;

(4) means for allowing equilibration of static pressures across said diaphragm means while maintaining acoustic separation across the diaphragm means;

(5) a first, pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured;

(6) a second, pressure-sensitive transducer for measuring pressure changes within said chamber of known volume;

(7) electrical circuit means connected to said first pressure-sensitive transducer and to said drive means, for sampling the electrical output of said first, pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged output signal from the signals generated by said electrical circuit means;

(8) means for generating a second output signal from the second, pressure-sensitive transducer; and

(9) comparator means for comparing said time-averaged output signal derived from the first, pressure-sensitive transducer with the second output signal derived from said second, pressure-sensitive transducer, and wherein said electrical circuit means comprises a first averaging element which is connected to said first transducer only during moments of maximum diaphragm excursion is one direction, and a second averaging element which is connected to said first transducer only during moments of maximum diaphragm excursion in the opposite direction, together with means for determining the difference between the outputs of said first and second averaging elements, said outputs representing, respectively, first and second averaged signals derived from the response of said free volume of said repeated compressions; and

wherein said comparator comprises a logic element which is arranged to calculate a value indicative of said free volume from the difference between said output signals derived from said first transducer and from the ouput signal derived from said second transducer.

9. Apparatus as claimed in claim 8, which further comprises display means responsive to the output of said comparator means.

12. Apparatus as claimed in claim 8 which is in portable form and which further comprises a duct communicating with said chamber of known volume, said duct acting as an extension of said chamber and supporting within it said diaphgram means, wherein (a) the duct terminates in a coupling for attachment to the volume which is to be measured;

and (b) said first, pressure-sensitive transducer is arranged and located so as to detect pressure variations within said duct between the diaphragm means and said coupling.

13. Apparatus as claimed in claim 12 which further includes means for flushing out the contents of said chamber of known volume.

14. Apparatus as claimed in claim 13 which comprises a by-pass duct located as a by-pass around said diaphragm means;

a one-way valve located in said by-pass duct so as to admit gases or vapours from upstream of the diaphragm means into the chamber of known volume downstream of the diaphragm means; and

a pump for withdrawing gas or vapour from said chamber of known volume.

17. Apparatus for measuring the free volume within a confined space which apparatus comprises (1) diaphragm means, for applying repeated compressions to said confined space or container;

(2) drive means for moving said diaphragm means in accordance with a predetermined waveform;

(3) a pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured;

(4) electrical circuit means connected to said pressure-sensitive transducer and to said drive means, for sampling the electrical output of said pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged output signal from the signals generated by said electrical circuit means; and

(5) means for determining from said time-averaged output signal a value representative of the free volume being measured, said electrical circuit means comprising a first averaging element which is connected to said transducer only during times of maximum diaphragm excursion in one direction, and a second averaging element which is connected to said transducer only during times of maximum diaphragm excursion in the opposite direction, together with means for determining the difference between the outputs of said first and said second averaging elements, said outputs representing, respectively, first and second averaged signals derived from the response of said free volume to said repeated compressions.

18. A portable Apparatus for measuring the free volume within a confined space, which apparatus comprises (1) diaphragm means, for applying repeated compressions to said confined space or container;

(2) a chamber of known volume supporting said diaphragm means;

(3) drive means for moving said diaphragm means in accordance with a predetermined waveform;

(4) means for allowing equilibration of static pressures across said diaphragm means while maintaining acoustic separation across the diaphragm means;

(5) a first, pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured;

(6) a second, pressure-sensitive transducer for measuring pressure changes within said chamber of known volume;

(7) electrical circuit means connected to said first pressure-sensitive transducer and to said drive means, for sampling the electrical output of said first, pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged ouput signal from the signals generated by said electrical circuit means;

(8) means for generating a second output signal from the second, pressure-sensitive transducer; and

(9) comparator means for comparing said time-averaged ouput signal derived from the first, pressure-sensitive transducer with the second ouput signal derived from said second, pressure-sensitive transducer, a duct communicating with said chamber of known volume, said duct acting as an extension of said chamber and supporting within it said diaphragm means, wherein (a) the duct terminates in a coupling for attachment to the volume which is to be measured, and (b) said first, pressure-sensitive transducer is arranged and located so as to detect pressure variations within said duct between the diaphragm means and said coupling.

19. Apparatus as claimed in claim 18 including means for flushing out the contents of said chamber of known volume and a by-pass duct located as a by-pass around said diaphragm means;

a one-way valve located in said by-pass duct so as to admit gases or vapours from upstream of the diaphragm means into the chamber of known volume downstream of the diaphragm means; and

a pump for withdrawing gas or vapour from said chamber of known volume.

20. Apparatus for measuring the free volue within a confined space which apparatus comprises (1) diaphragm means, for applying repeated compressions to said confined space or container;

(2) drive means for moving said diaphragm means in accordance with a squarewave waveform;

(3) a pressure-sensitive transducer for measuring pressure changes within the volume which is itself to be measured;

(4) electrical circuit means connected to said pressure-sensitive transducer and to said drive means, for sampling the electrical output of said pressure-sensitive transducer at predetermined times related to the frequency at which the diaphragm means is driven and for generating a time-averaged output signal from the signals generated by said electrical circuit means; and

(5) means for determining from said time-averaged ouput signal a value representative of the free volume being measured.