Acoustical volume/pressure measurement device

• US 4,704,902 A
• Filed: 07/10/1986
• Issued: 11/10/1987
• Est. Priority Date: 12/04/1984
• Status: Expired due to Fees

• Current Assignee: Navin H. Doshi
• Original Assignee: Navin H. Doshi
• Inventors: Doshi, Navin H.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US06/883,911
• Time in Patent Office: 488 Days
• Field of Search: 73/49.2, 73/149, 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
• CPC Class Codes: G01F 23/296 Acoustic waves

Abstract

The apparatus consists of a mechanical acoustical driver producing sound vibrations in a fluid, such as a liquid or gas, within an enclosed space. A pickup transducer positioned within the tank measures the sound vibrations of the gas within the tank and transmits the same to an amplifier and a low pass filter. Either the same or another transducer positioned in the tank measures static pressure P output of which is amplified. A divider circuit receives the dynamic pressure signal and static pressure signal and provides electrical signal E proportional to (ΔP/P). A differential amplifier receives the reference signal Erf and the signal E and supplies the error signal (Erf-E) to a gain controlled amplifier. The gain controlled amplifier amplifies the AC signal proportional to (Erf-E). The driver generates ΔP in the tank proportional to the output of the gain controlled amplifier.

Claims

1. An apparatus for measuring the volume of a gas in an enclosed space, comprising:

means for producing a dynamic pressure in the gas;

means for measuring the dynamic pressure;

means for measuring static pressure of the gas;

feedback control means for feeding measurements from said means for measuring dynamic pressure and said means for measuring static pressure to control said means for producing so that a ratio of the dynamic pressure to the static pressure is a selected constant.

2. The apparatus of claim 1 wherein said means for measuring dynamic pressure has an electrical output.

3. The apparatus of claim 2 wherein said means for measuring static pressure has an electrical output.

4. The apparatus of claim 3 further including a means for converting the measurement from said means for measuring dynamic pressure to a dc output.

5. The apparatus of claim 4 further including a means for receiving the output from said means for measuring dynamic pressure and said means for measuring static pressure and producing an output proportional to a ratio of the output from said means for measuring dynamic pressure and said means for measuring static pressure.

6. The apparatus of claim 5 further including:

a differential amplifier;

means for supplying a reference signal to said differential amplifier, said differential amplifier having an output proportional to the difference between the reference signal and the output from said means for receiving.

7. The apparatus of claim 6 further including:

a power amplifier, and

an oscillator, said oscillator having an output feeding into said power amplifier to produce a signal output from said power amplifier having a selected frequency, said power amplifier receiving the output from said differential amplifier, said power amplifier having a selected gain, the gain being sufficiently high to produce an output having a selected range of amplitudes to control the amplitude of oscillation of the means for producing a dynamic pressure so that the output from said means for receiving approaches but does not equal the reference signal.

8. The apparatus of claim 1 wherein said feedback control means includes a closed loop servo system having a very high gain within the range of 1,000 to 1,000,000 so that the ratio of the dynamic pressure to the static pressure is a selected constant.

9. An apparatus for measuring the specific heat ratio of a gas in an enclosed space, comprising:

means for producing a dynamic pressure in the gas;

means for measuring the dynamic pressure;

means for measuring the static pressure of the gas;

feedback control means for feeding measurements from said means for measuring dynamic pressure and and said means for measuring static pressure to control said means for producing so that a ratio of the dynamic pressure to the static pressure is a selected constant in order to obtain a measurement of the specific heat ratio in accordance with the formula;

space="preserve" listing-type="equation">Δ

P/P=γ

Δ

V/V=A (a constant)

γ

approaches 1.0 at very low frequency measurements (isothermal process)

space="preserve" listing-type="equation">Δ

V.sub.l =(A) (V) at very low frequency measurements

space="preserve" listing-type="equation">Δ

V.sub.h =(1/γ

) (V) (A) at higher (adiabetic) frequency measurements

space="preserve" listing-type="equation">γ

=Δ

V.sub.l /Δ

V.sub.h

where

Δ

V_l =dynamic volume at low frequency measurement

Δ

V_h =dynamic volume at high frequency measurement.

10. An apparatus for measuring the volume of a gas within an enclosed space, comprising:

means for emitting sound in the gas;

means for measuring the dynamic pressure change of the gas induced by the means for emitting sound;

means for measuring the static pressure change of the gas;

a dynamic pressure signal conditioner for converting output from said means for measuring the dynamic pressure into a dc current output;

a divider for receiving the output from said means for measuring the dynamic pressure and the output from said means for measuring the static pressure and producing a dc output proportional to the ratio of the output of said means for measuring the dynamic pressure to the output of said means for measuring the static pressure;

means for applying a reference signal;

a differential amplifier, said amplifier receiving the output from said divider and the reference signal, said amplifier amplifying the difference between said reference signal and the output from said divider;

an oscillator having a selected sinusoidal output;

a power amplifier, said power amplifier receiving the sinusoidal output and the output from said divider, said power amplifier amplifying the sinusoidal signal by an amount proportional to the output from the differential amplifier, the output from said power amplifier driving said means for emitting sound, the output from said power amplifier increasing or decreasing the amplitude of oscillation of the means for emitting proportional to the output from the differential amplifier such that the oscillation of the means for emitting is altered to result in change in the dynamic pressure to minimize the difference between the reference signal and the divider output;

means for measuring the voltage of the output from said power amplifier.

11. The apparatus of claim 10 further including a static pressure signal conditioner receiving the output from said means for measuring the static pressure, said static pressure conditioner amplifying the output from said means for measuring and filtering the output from said means for measuring the static pressure to remove undesired signals therefrom.

12. The apparatus of claim 10 wherein said dynamic signal conditioner amplifies the output from said means for measuring the dynamic pressure and filters the output from said means for measuring the dynamic pressure to remove undesired signals therefrom.