Method and apparatus for measuring the liquid level of a containment tank subject to external forces

• US 5,133,212 A
• Filed: 08/12/1991
• Issued: 07/28/1992
• Est. Priority Date: 08/12/1991
• Status: Expired due to Term

• Current Assignee: Kaiser Aerospace & Electronics Corporation
• Original Assignee: Kaiser Aerospace & Electronics Corporation
• Inventors: Kamenoff, Robert, Grills, Laurence M.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): WORTH, WILLIE M
• Application Number:
  US07/745,063
• Time in Patent Office: 351 Days
• Field of Search: 73/296, 340/613, 340/618, 364/556, 364/567
• US Class Current: 73/296
• CPC Class Codes: G01F 23/20 by measurement of weight, e.g. to determine the level of stored liquefied gas
• CPC Class Codes: G01F 23/804 containing circuits handling parameters other than liquid level
• CPC Class Codes: G01G 17/04 for weighing fluids, e.g. gases, pastes

Abstract

A detection system for determining the level of a liquid in a containment tank includes a containment tank and a reference standard of known weight mounted to the vehicle and movable along the yaw axis of the vehicle. Load cells are placed intermediate the tank and reference standard to provide analog voltage outputs in proportion to the load on each cell. The load cell outputs, when amplified, summed and then divided by the output of the reference weight load cell, provide an electronic signal that is proportional to the gross weight of the tank. A pre-set signal, representative of the empty weight of the tank, is subtracted from the gross weight signal, resulting in a signal which is proportional to the net weight, or the contents of the tank.

Claims

1. An apparatus for use in measuring the volume or level of a liquid in a containment tank in a vehicle that is subject to external forces caused by movement of the vehicle having several degrees of freedom, comprising:

a containment tank mounted to the vehicle and subject to forces along the yaw axis of the vehicle;

a reference standard of known weight mounted to the vehicle and subject to forces along the yaw axis of the vehicle;

at least two tank strain gauge load cells sensed by applied electrical energy for providing analog electrical outputs proportionally representing the load on each load cell, said load cells being placed intermediate separated portions of said containment tank and a portion of a common reference surface of the vehicle, said load cells being sensitive along a first axis that is substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

at least one reference strain gauge load cell capable of providing analog electrical outputs proportionately representing the load on said reference load cell, said reference load cell being placed intermediate said reference standard and a portion of said common reference surface, and sensitive generally along a second axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle and said first axis;

means for retaining data representative of the known tank empty weight; and

,

computational means to convert said analog electrical output signals essentially simultaneously into output information representative of the volume or level of the liquid in the containment tank by summing the plurality of tank load cell output signals to generate a tank gauge sum signal, dividing said tank gauge sum signal by the output of said reference load cell to generate a tank gross weight signal, and then subtractively combining a tank weight signal representative of the known tank empty weight with said tank gross weight signal to generate a tank net weight signal.

2. An apparatus as in claim 1, further including:

means for electrically averaging out short term transients appearing in the analog signals as a result of inertial forces of the contents of said tank.

3. An apparatus as in claim 1, wherein said computational means further includes:

a plurality of cell signal amplifier means, each operationally connected to a corresponding one of said plurality of tank strain gauge load cells, for amplifying the analog voltage output from said plurality of tank strain gauge load cells.

4. An apparatus as in claim 3, wherein said computational means further includes:

a reference amplifier means operationally connected to said reference strain gauge load cell for amplifying the analog voltage output from said reference strain gauge load cell.

5. An apparatus as in claim 4, wherein said computational means further includes:

analog multiplier means operationally coupled with said tank strain gauge load cell amplifier means and said reference strain gauge load cell amplifier means, for dividing said tank gauge sum signal by the output of said reference load cell output to generate said tank gross weight signal.

6. An apparatus as in claim 5, wherein said computational means further includes:

subtraction amplifier means operationally coupled with said analog multiplier means and said memory means for subtractively combining said known tank empty weight signal with said tank gross weight signal to generate said tank net weight signal, and to convert said tank net weight signal to a signal representative of the volume or level of liquid in the tank.

7. An apparatus as in claim 1, further including:

tank liquid level readout means linked to said computational means for displaying said signal representative of the volume or level of the liquid contained in said tank.

8. An apparatus for use in measuring the volume or level of a liquid in a containment tank in a vehicle that is subject to external forces caused by movement of the vehicle, comprising:

a containment tank mounted to the vehicle and movable along the yaw axis of the vehicle;

a reference standard of known weight mounted to the vehicle and movable along the yaw axis of the vehicle;

a plurality of tank strain gauge load cells sensed by direct current voltage means providing analog voltage outputs in proportion to the load on each load cell, said plurality of load cells being placed intermediate different portions of said containment tank and a portion of a common reference surface of the vehicle, and sensitive along a first axis that is substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

at least one reference strain gauge load cell providing analog voltage outputs in proportion to the load on said reference cell, said reference cell being placed intermediate said reference standard and a portion of said common reference surface, and aligned generally parallel to a second axis that is substantially normal to said common reference surface and substantially parallel to said first axis and the yaw axis of the vehicle;

means to convert the analog voltage outputs from said tank load cells and from said reference load cell into digital signals;

correcting means for retaining data representative of the known tank empty weight; and

,

computational means to convert the digital signals essentially simultaneously into output information representative of the volume or level of the liquid in the containment tank by summing the plurality of tank load cell outputs to form a summed signal, dividing said summed signal by the output of said reference load cell to generate a tank gross weight signal, and then subtractively combining a known tank empty weight signal representative of the known tank empty weight from said correcting means with said tank gross weight signal to generate a tank net weight signal.

9. A method for use in measuring the volume or level of a liquid in a containment tank in a vehicle that is subject to external forces caused by movement of the vehicle, comprising the steps of:

mounting a containment tank to the vehicle so that it is movable along the yaw or vertical axis of the vehicle;

mounting a reference standard of known weight to the vehicle so that it is movable along the yaw or vertical axis of the vehicle;

placing a plurality of tank strain gauge load cells sensed by direct current voltage means providing analog voltage outputs in proportion to the load on each load cell, intermediate different portions of said containment tank and a portion of a common reference surface of the vehicle, and sensitive along an axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

placing at least one reference strain gauge load cell sensed by direct current voltage means providing analog voltage outputs in proportion to the load on the load cell intermediate said reference standard of known weight and a portion of said common reference surface of the vehicle, and sensitive generally parallel along an axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle; and

,

converting the analog signals, essentially simultaneously, into output information representative of the volume or level of the liquid in the containment tank by summing the plurality of tank load cell outputs to form a sum signal, dividing said sum signal by the output of said reference load cell output to form a tank gross weight signal, and then subtractively combining a known tank empty weight signal representative of the known tank empty weight with said tank gross weight signal to generate a tank net weight signal.

10. A method for use in measuring the volume or level of a liquid in a containment tank in a vehicle subject to external forces caused by movement of the vehicle, comprising the steps of:

mounting a containment tank to the vehicle so that it is movable along the yaw or vertical axis of the vehicle;

mounting a reference standard of known weight to the vehicle so that it is movable along the yaw or vertical axis of the vehicle;

placing a plurality of tank strain gauge load cells sensed by direct current voltage means providing analog voltage outputs in proportion to the load on each load cell, intermediate different portions of said containment tank and a portion of a common reference surface of the vehicle, and aligned along an axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

placing at least one reference strain gauge load cell sensed by direct current voltage means providing analog voltage outputs in proportion to the load on the load cell, intermediate said reference standard of known weight and a portion of said common reference surface, and aligned generally parallel along an axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

converting the analog voltage outputs from the tank load cells and from the reference load cell into digital signals;

converting the digital signals, essentially simultaneously, into output information of the volume or level of the liquid in the containment tank by summing the plurality of tank load cell outputs to form a sum signal, dividing said sum signal by the output of said reference load cell output to form a tank gross weight signal, and then subtractively combining a known tank empty weight signal representative of the known tank empty weight with said tank gross weight signal to generate a tank net weight signal; and

,

converting said tank net weight signal into a liquid level signal corresponding volume or level of liquid contained in the tank.

11. An apparatus for use in measuring the weight of a liquid in a containment tank in a vehicle that is subject to external forces caused by movement of the vehicle having several degrees of freedom, comprising:

a containment tank mounted to the vehicle and subject to forces along the yaw axis of the vehicle;

a reference standard of known weight mounted to the vehicle and subject to forces along the yaw axis of the vehicle;

at least two tank strain gauge load cells located intermediate separated portions of said containment tank and a portion of a common reference surface of the vehicle, for providing analog electrical load outputs proportionally representing the load on each load cell, said load cells being sensitive along a first axis that is substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle;

at least one reference strain gauge load cell located intermediate said reference standard and a portion of said common reference surface, for providing analog electrical reference outputs proportionately representing the load on said reference load cell, said reference load cell being sensitive generally along a second axis substantially normal to said common reference surface and generally parallel to the yaw axis of the vehicle and said first axis; and

,

computational means coupled to receive said load output signals and said reference output signals, for summing said load signals to generate a sum signal, dividing said sum signal by said reference signal to generate a tank gross weight signal, and for subtractively combining an applied tank weight signal representative of the known tank empty weight with said tank gross weight signal to generate a tank net weight signal.