Acoustic adiabatic liquid quantity sensor

A system for measuring the volume of a liquid, powder or solid material in a main closed chamber of known empty volume, comprising;

• a reference chamber having a known empty volume V2 and mounted adjacent a surface of said main chamber;
• means for equalizing the static gas pressure in the respective main and reference chambers, wherein said equalizing means comprises one or more open passages disposed in said surface communicating between said reference chamber and said main chamber;
• an excitation transducer mounted between and dividing the main and reference chambers to produce a volume displacement in the respective chambers;
• an excitation source for generating an excitation signal for driving said excitation transducer;
• a main chamber pressure transducer disposed within said main chamber for providing a main transducer signal indicative of the differential gas pressures ΔP1 in the main chamber caused by the volume displacement;
• a reference chamber pressure transducer disposed within said reference chamber for providing a reference transducer signal indicative of the differential gas pressure ΔP2 in the reference chamber caused by said volume displacement;
• and
• means responsive to the main and reference transducer signals for providing a signal indicative of the gas volume of said material in the main chamber in dependence on said known empty volume and said reference chamber volume V2.

A quantity gauge system for measuring the volume of a solid, gas, or liquid material in a main closed chamber of known empty volume, comprising:

• a reference chamber having a known empty volume V2 and mounted in a back-to-back configuration with a surface of said main chamber;
• means for equalizing the static gas pressure in the respective main and reference chambers;
• an excitation transducer for producing a volume displacement in the respective chambers;
• an excitation source for generating an excitation signal for driving the excitation transducer;
• a main chamber pressure sensing means for providing a main transducer signal indicative of the differential gas pressure P1 in the main chamber caused by the volume displacement;
• a reference chamber pressure sensing means for providing a reference transducer signal indicative of the differential gas pressure P2 in the reference chamber caused by said volume displacement;
• means responsive to the main and reference transducer signals for providing a quantity signal indicative of the quantity of material in the main chamber in dependence on said volume V2 and said known empty volume of said main chamber, wherein said equalizing means comprises one or more open passages communicating between said reference chamber and said main chamber, said passages characterized by a characteristic cutoff frequency, and wherein during a system measurement mode of operation when said volume of said material in said main chamber is to be measured, the frequency or frequencies of said transducer drive signal is greater than said cutoff frequency.

A system for measuring the volume V1 of a gas in a main closed chamber, comprising:

• a reference chamber having a known volume V2 and mounted in a back-to-back configuration with a common surface of said main chamber, the surface between and dividing the main and reference chambers;
• means disposed in said surface for equalizing the static gas pressure in the respective main and reference chambers, said equalizing means comprising one or more open passages communicating between said reference chamber and said main chamber, said one or more passages characterized by a characteristic cutoff frequency;
• an excitation transducer for producing a volume displacement in the respective chambers;
• an excitation source for generating an excitation signal for driving the excitation transducer, wherein the frequency or frequencies of said excitation signal is selected so that compressions and rarefactions of the gases in said main and reference chambers resulting from said excitation signal are nearly adiabatic, and standing waves and resonances are not excited in said chambers;
• a main chamber pressure sensing means for providing a main transducer signal indicative of the differential gas pressure ΔP1 in the main chamber caused by the volume displacement;
• a reference chamber pressure sensing means for providing a reference transducer signal indicative of the differential gas pressure ΔP2 in the reference chamber caused by said volume displacement;
• and
• means responsive to the main and reference transducer signals for providing a signal indicative of the gas volume V1 in the main chamber;
• and
• wherein during a system measurement mode of operation when said volume of gas in said main chamber is to be measured, said excitation signal is characterized by frequency components greater than said cutoff frequency.

A system for measuring the volume of a liquid, powder or solid material in a main closed chamber of known empty volume, comprising:

• a reference chamber having a known empty volume V2 and mounted back-to-back with a surface of said main chamber, the surface between and dividing the main and reference chambers;
• means disposed in said surface for equalizing the static gas pressure in the respective main and reference chambers, said equalizing means comprising one or more open passages communicating between said reference chamber and said main chamber, said one or more passages characterized by a characteristic cutoff frequency;
• an excitation transducer for producing a volume displacement in the respective chambers;
• an excitation source for generating an excitation signal for driving said excitation transducer;
• a main chamber pressure sensing means for providing a main transducer signal indicative of the differential gas pressure ΔP1 in the main chamber caused by the volume displacement;
• a reference chamber pressure sensing means for providing a reference transducer signal indicative of the differential gas pressure ΔP2 in the reference chamber caused by said volume-displacement;
• means responsive to the main and reference transducer signals for providing a signal indicative of the gas volume of said material in the main chamber in dependence on said known empty volume and said reference chamber volume V2;
• and
• wherein during a system measurement mode of operation when said volume of said gases in said main chamber is to be measured the frequency or frequencies of said excitation signal is greater than said cutoff frequency.