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A capacitive gauge, suitable for measuring a fluid level in a container, includes upper and lower capacitive elements. Also provided is a control unit for calculating the fluid level in the container based on the capacitance of the upper and lower capacitors and a dielectric constant of the fluid in

A capacitive gauge, suitable for measuring a fluid level in a container, includes upper and lower capacitive elements. Also provided is a control unit for calculating the fluid level in the container based on the capacitance of the upper and lower capacitors and a dielectric constant of the fluid in the container. The control unit also includes functionality for determining and storing the dielectric constant of the fluid in the container. The dielectric constant of the fluid is determined by first verifying whether the lower capacitive element is completely submerged based on a comparison of a measured capacitance of the upper capacitor to a reference capacitance of the upper capacitor. If the lower capacitor is verified to be submerged, then the dielectric constant of the fluid is calculated based on a measured capacitance of the lower capacitor.

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1. A gauge suitable for measuring a level of fluid in a container, the gauge comprising:a first capacitive element having a measured capacitance that varies for a first range of fluid levels; a second capacitive element having a measured capacitance that varies for a second range of fluid levels; a

1. A gauge suitable for measuring a level of fluid in a container, the gauge comprising:a first capacitive element having a measured capacitance that varies for a first range of fluid levels; a second capacitive element having a measured capacitance that varies for a second range of fluid levels; a nonvolatile memory for storing a reference capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid; and a control unit for determining whether conditions are satisfactory for performing a calibration routine, wherein the control unit determines whether conditions are satisfactory based on a comparison of the measured capacitance of said first capacitive element to the reference capacitance of said first capacitive element, wherein, when said conditions are determined to be satisfactory, the control unit determines a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element. 2. A gauge according to claim 1, wherein reference information related to said second capacitive element is stored in the nonvolatile memory.3. A gauge according to claim 2, wherein the calculation for determining the dielectric constant of the fluid uses the measured capacitance of said second capacitive element and the reference information related to said second capacitive element.4. A gauge according to claim 1, wherein the control unit determines conditions are unsatisfactory for performing said calibration routine if the measured capacitance of said first capacitive element is equal to the reference capacitance of said first capacitive element.5. A gauge according to claim 1, further comprising an input section for inputting to the control unit the measured capacitance of said first capacitive element and inputting to the control unit the measured capacitance of said second capacitive element.6. A gauge according to claim 1, wherein, when the control unit calculates the dielectric constant, the control unit stores the thus calculated dielectric constant in the nonvolatile memory.7. A gauge according to claim 1, wherein at least one entire conductive surface of said second capacitive element is disposed below at least one conductive surface of said first capacitive element relative to the fluid level being monitored.8. A gauge suitable for measuring a level of fluid in a container, the gauge comprising:a first capacitive element having a measured capacitance that varies for a first range of fluid levels; a second capacitive element having a measured capacitance that varies for a second range of fluid levels; a nonvolatile memory for storing a reference capacitance of said second capacitive element representative of a situation where none of said second capacitive element is submerged in the fluid; and a control unit for determining whether conditions are satisfactory for performing a calibration routine, wherein, when said conditions are determined to be satisfactory, the control unit determines a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element and the reference capacitance of said second capacitive element, wherein at least one entire conductive surface of said second capacitive element is disposed below at least one conductive surface of said first capacitive element relative to the fluid level being monitored, and wherein the determination by the control unit that the conditions for performing a calibration routine are satisfactory includes verifying that said second capacitive element is completely submerged in the fluid. 9. A gauge according to claim 8, wherein the verification by the control unit that said second capacitive element is completely submerged in the fluid includes verifying that said second capacitive element is completely submerged in the fluid by determining if any portion of said first capacitive element is submerged in the fluid.10. A gauge according to claim 9, wherein the determination, by the control unit, that any portion of said first capacitive element is submerged includes determining if any portion of said first capacitive element is submerged in the fluid by comparing the measured capacitance of said first capacitive element to a reference capacitance of said first capacitive element.11. A gauge according to claim 10, wherein the reference capacitance of said first capacitive element is a capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid.12. A calibration system for a fluid-level gauge, the gauge having first and second capacitive elements, each of the capacitive elements having a capacitance that varies within a respective range of fluid levels, the system comprising:a measuring section for determining a measured capacitance of the first capacitive element and a measured capacitance of the second capacitive element; a memory for storing a reference capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid; a comparing section for determining a comparison value based on a comparison of the measured capacitance of said first capacitive element and the reference capacitance of said first capacitive element, a calculating section for determining, based on the comparison value, whether conditions are satisfactory for performing a calibration routine, and for, when said conditions are determined to be satisfactory, determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element. 13. A calibration system according to claim 12, wherein the memory stores reference information regarding said second capacitive element.14. A calibration system according to claim 13, wherein the calculation for determining the dielectric constant of the fluid involves the measured capacitance of said second capacitive element and the reference information regarding said second capacitive element.15. A calibration system for a fluid-level gauge, the gauge having first and second capacitive elements, each of the capacitive elements having a capacitance that varies within a respective range of fluid levels, the system comprising:a measuring section for determining a measured capacitance of the first capacitive element and a measured capacitance of the second capacitive element; a memory for storing a reference capacitance of said second capacitive element representative of a situation where none of said second capacitive element is submerged in the fluid; a calculating section for determining whether conditions are satisfactory for performing a calibration routine, and for, when said conditions are determined to be satisfactory, determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element and the reference capacitance of said second capacitive element, wherein the memory stores a reference capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid, further comprising a comparing section for determining a comparison value based on a comparison of the measured capacitance of said first capacitive element and the reference capacitance of said first capacitive element, wherein the calculating section uses the comparison value for a calculation for determining whether said conditions are satisfactory. 16. A gauge suitable for measuring a level of fluid in a container, the gauge comprising:a first capacitive element having a capacitance that varies for a first range of fluid levels; a second capacitive element having a capacitance that varies for a second range of fluid levels; a nonvolatile memory for storing a reference capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid; and a control unit for determining, based on a comparison of a measured capacitance of said first capacitive element to the reference capacitance of said first capacitive element, whether conditions are satisfactory for proceeding with calculating a dielectric constant of the fluid, wherein, when said conditions are determined to be satisfactory, the control unit calculates the dielectric constant of the fluid based on a calculation involving a measured capacitance of said second capacitive element and reference information about said second capacitive element. 17. A gauge according to claim 16, wherein the first range of fluid levels and the second range of fluid levels are mutually exclusive.18. A gauge according to claim 17, wherein the second range of fluid levels is lower than the first range of fluid levels.19. A gauge according to claims 16, wherein, when said conditions are determined to be satisfactory, and the control unit determines the dielectric constant of the fluid, the thus determined dielectric constant is stored in the nonvolatile memory.20. A gauge according to claim 19, the control unit determines an amount of fluid based on a calculation including the dielectric constant stored in the nonvolatile memory.21. A gauge according to claim 19, wherein, when said conditions are not determined to be satisfactory, the control unit does not continue with making a calculation of the dielectric constant.22. A gauge suitable for measuring a level of fluid in a container, the gauge comprising:a first capacitive element having a capacitance that varies for a first range of fluid levels; a second capacitive element having a capacitance that varies for a second range of fluid levels; a nonvolatile memory for storing a reference capacitance of said second capacitive element representative of a situation where none of said second capacitive element is submerged in the fluid; and a control unit for determining, based on a measured capacitance of said first capacitive element, whether conditions are satisfactory for proceeding with calculating a dielectric constant of the fluid, wherein, when said conditions are determined to be satisfactory, the control unit calculates the dielectric constant of the fluid based on a calculation involving a measured capacitance of said second capacitive element and the reference capacitance of said second capacitive element, wherein, when said conditions are determined to be satisfactory, and the control unit determines the dielectric constant of the fluid, the thus determined dielectric constant is stored in the nonvolatile memory, wherein, when said conditions are not determined to be satisfactory, the control unit does not continue with making a calculation of the dielectric constant, and wherein, when the control unit does not make a calculation of the dielectric constant, the control unit makes subsequent determinations of amounts of fluid based on a calculation including a dielectric constant previously stored in the nonvolatile memory at least until a next determination is made by the control unit as to whether said conditions are satisfactory for proceeding with calculating the dielectric constant of the fluid. 23. A method of maintaining the calibration of a gauge for measuring a level of fluid, the gauge having first and second capacitive elements, each of the capacitive elements having a capacitance that varies within a respective range of fluid levels, the method comprising the steps of:(a) determining a measured capacitance of the first capacitive element; (b) determining whether conditions are satisfactory for performing a calibration routine based on a comparison of the measured capacitance of said first capacitive element to a reference capacitance of said first capacitive element; and (c) if said conditions are determined to be satisfactory in step (b), performing the steps of: (c1determining a measured capacitance of the second capacitive element, (c2) obtaining previously stored reference information related to said second capacitive element, and (c3) determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element and the reference information related to said second capacitive element. 24. A method according to claim 23, wherein the reference capacitance of said first capacitive element is a capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid.25. A method according to claim 24, wherein step (b) includes retrieving the reference capacitance of said first capacitive element from a nonvolatile memory.26. A method according to claim 23, wherein step (c) includes the step of:(c4) storing the dielectric constant calculated in step (c3) in a nonvolatile memory. 27. A method of maintaining the calibration of a gauge for measuring a level of fluid, the gauge having first and second capacitive elements, each of the capacitive elements having a capacitance that varies within a respective range of fluid levels, the method comprising the steps of:(a) determining a measured capacitance of the first capacitive element; (b) determining whether conditions are satisfactory for performing a calibration routine based on the measured capacitance of said first capacitive element; and (c) if said conditions are determined to be satisfactory in step (b), performing the steps of: (c1) determining a measured capacitance of the second capacitive element, (c2) obtaining a previously stored reference capacitance of said second capacitive element representative of a situation where none of said second capacitive element is submerged in the fluid, and (c3) determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element and the reference capacitance of said second capacitive element, wherein in step (b) the determination as to whether conditions are satisfactory is based on a comparison of the measured capacitance of said first capacitive element to a reference capacitance of said first capacitive element, wherein the reference capacitance of said first capacitive element is a capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid, and wherein in step (b) the determination is made that conditions are unsatisfactory for performing said calibration routine if the measured capacitance of said first capacitive element is equal to the reference capacitance of said first capacitive element. 28. A method of maintaining the calibration of a gauge for measuring a level of fluid, the gauge having first and second capacitive elements, each of the capacitive elements having a capacitance that varies within a respective range of fluid levels, the method comprising the steps of:(a) determining a measured capacitance of the first capacitive element; (b) determining whether conditions are satisfactory for performing a calibration routine based on the measured capacitance of said first capacitive element; and (c) if said conditions are determined to be satisfactory in step (b), performing the steps of: (c1) determining a measured capacitance of the second capacitive element, (c2) obtaining a previously stored reference capacitance of said second capacitive element representative of a situation where none of said second capacitive element is submerged in the fluid, and (c3) determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element and the reference capacitance of said second capacitive element, wherein step (b) includes verifying that said second capacitive element is completely submerged in the fluid. 29. A method according to claim 28, wherein step (b) includes verifying that said second capacitive element is completely submerged in the fluid by determining if any portion of said first capacitive element is submerged in the fluid.30. A method according to claim 29, wherein step (b) includes determining if any portion of said first capacitive element is submerged in the fluid by comparing the measured capacitance of said first capacitive element to a reference capacitance of said first capacitive element.31. A method according to claim 30, wherein the reference capacitance of said first capacitive element is a capacitance of said first capacitive element representative of a situation where none of said first capacitive element is submerged in the fluid.32. A method of measuring a level of fluid comprising the steps of:(a) determining a measured capacitance of a first capacitive element having a capacitance that varies within a first range of fluid levels; (b) determining whether conditions are satisfactory for performing a calibration routine based on a comparison between the measured capacitance of said first capacitive element and a reference capacitance of said first capacitive element; (c) if said conditions are determined to be satisfactory in step (b), performing the steps of: (c1) determining a measured capacitance of said second capacitive element having a capacitance that varies within a second range of fluid levels mutually exclusive from said first range of fluid levels, (c2) obtaining previously stored reference information related to said second capacitive element, (c3) determining a dielectric constant of the fluid based on a calculation involving the measured capacitance of said second capacitive element, and (c4) calculating a fluid level based at least in part on the dielectric constant determined in step (c3); and (d) if said conditions are determined to not be satisfactory in step (b), calculating the fluid level based at least in part on a previously determined dielectric constant. 33. A method according to claim 32, wherein, in step (d), the previously determined dielectric constant is a dielectric constant stored in a nonvolatile memory during manufacturing.34. A method according to claim 32, wherein step (c) includes the step of:(c5) storing the dielectric constant calculated in step (c3) in a nonvolatile memory. 35. A method according to claim 34, wherein, in step (d), the previously determined dielectric constant is a dielectric constant stored in the nonvolatile memory during a previously performed calibration routine.36. A method according to claim when said previous performed calibration routine includes previously performed steps (c1), (c2), (c3), and (c5).