초록 ▼

A method of determining level of a liquid between empty and full conditions within a container includes: providing first and second elongate capacitors, each capacitor being independently capable of measuring the liquid level at least between the empty and full conditions within the container, with

A method of determining level of a liquid between empty and full conditions within a container includes: providing first and second elongate capacitors, each capacitor being independently capable of measuring the liquid level at least between the empty and full conditions within the container, with the second capacitor being longer than the first capacitor; determining first and second capacitance values for the first and second capacitors, respectively, based on the liquid level height; and dividing the first capacitance value by a difference between the second and first capacitance values to thereby obtain a liquid level value independent of the dielectric constant.

대표청구항 ▼

1. A method of determining level of a liquid between empty and full conditions within a container, the liquid having a dielectric constant, the method comprising: providing first and second elongate capacitors, each capacitor being independently capable of measuring the liquid level at least between

1. A method of determining level of a liquid between empty and full conditions within a container, the liquid having a dielectric constant, the method comprising: providing first and second elongate capacitors, each capacitor being independently capable of measuring the liquid level at least between the empty and full conditions within the container, with the second capacitor being longer than the first capacitor;determining first and second capacitance values for the first and second capacitors, respectively, based on the liquid level height; anddividing the first capacitance value by a difference between the second and first capacitance values to thereby obtain a first liquid level value independent of the dielectric constant. 2. A method according to claim 1, and further comprising: assigning a first coefficient value dependent on a geometrical difference between the first and second capacitors; andapplying the first coefficient value to the first liquid level value to obtain a second liquid level value. 3. A method according to claim 2, wherein the step of assigning at least one coefficient value comprises dividing the difference between lengths of the second and first capacitors by the length of the first capacitor. 4. A method according to claim 3, wherein the step of applying the first coefficient value comprises multiplying the first coefficient value with the first liquid level value. 5. A method according to claim 4, and further comprising: assigning a second coefficient value by dividing a first segment length of the first capacitor between a lower end of the first capacitor and a predetermined empty level thereof by the length of the first capacitor; andsubtracting the second coefficient value from the second liquid level value to obtain a third liquid level value. 6. A method according to claim 5, and further comprising: assigning a third coefficient value by dividing a second segment length of the first capacitor between the lower end of the first capacitor and a predetermined full level thereof by the length of the first capacitor; anddividing the third liquid level value by the third coefficient value to obtain a fourth liquid level value reflective of the level of liquid in the container. 7. A method according to claim 6, wherein the first segment length is at least substantially equal to the difference between lengths of the second and first capacitors. 8. A method according to claim 5, wherein the first segment length is at least substantially equal to the difference between lengths of the second and first capacitors. 9. A method according to claim 1, wherein the step of determining first and second capacitance values includes determining a dry capacitance value for each capacitor, measuring a wet capacitance value for each capacitor; and subtracting the dry capacitance value from the wet capacitance value for each capacitor. 10. A method according to claim 9, and further comprising indicating an empty condition of the container by determining whether at least one of the first and second capacitance values is approximately equal to the dry capacitance value. 11. A method according to claim 10, and further comprising indicating an empty condition of the container when the first liquid value is less than unity. 12. A method according to claim 1, and further comprising indicating an empty condition of the container when the first liquid value is less than unity. 13. A method of determining level of a liquid between empty and full conditions within a container, the liquid having a dielectric constant, the method comprising: providing first and second elongate capacitors, each capacitor being independently capable of measuring the liquid level at least between the empty and full conditions within the container, the first capacitor having a length L1 and the second capacitor having a length L2 longer than the first capacitor;dividing the first and second capacitors into a plurality of equal segments, with the second capacitor having one more segment than the first capacitor;assigning coefficient values as follows: K=Δ⁢⁢LL⁢⁢1;K0=L⁢⁢0L⁢⁢1;K100=L⁢⁢100L⁢⁢1where ΔL is the difference in length between L2 and L1 and L100 is the length of the first capacitor between a lower end thereof and a predetermined full tank condition with L100 being less than L1;determining first and second capacitance values for the first capacitor C1 and the second capacitor C2, respectively, as follows: C1d=C1m−C1a C2d=C2m−C2a where C1d is the determined capacitance of the first capacitor C1 and C2d is the determined capacitance of the second capacitor C2;determining an empty condition of the container when the first capacitance value C1d is approximately equal to a dry capacitance value;if the first capacitance value is not approximately equal to the dry capacitance value then determining a difference between the capacitances ΔCd as follows: ΔCd=C2d−C1d determining an empty condition of the container when ΔCd is less than unity; andif ΔCd is not less than unity then determining a liquid level value Lx of the container as follows: Lx=K×C⁢⁢1m-C⁢⁢1aC⁢⁢2m-C⁢⁢2a-(C⁢⁢1a-C⁢⁢1a)-K0K100-K0and; utilizing the liquid level value Lx to display and/or control the level of liquid in the container. 14. A method according to claim 13, wherein: L0≡ΔL; andL100≡5×ΔL; such that: Lx=14⁢(C⁢⁢1M-C⁢⁢1AC⁢⁢2M-C⁢⁢2A-(C⁢⁢1M-C⁢⁢1A)-1). 15. A capacitive sensor assembly for determining level of a liquid between empty and full conditions within a container, the capacitive sensor assembly comprising: an electronics section for receiving and processing signals related to capacitance measurements for determining the liquid level within the container; anda capacitive probe section connected to the electronics section comprising: a first elongate measurement capacitor having a first elongate conductive plate with a first length that extends from a position below the empty condition to a position above the full condition;a second elongate measurement capacitor having a second elongate conductive plate with a second length that extends from a position below the first elongate measurement capacitor to a position above the full condition, the second length being greater than the first length; andat least a third elongate conductive plate spaced from the first and second plates a predetermined distance to thereby form a gap for receiving the liquid to be measured, the first and second plates being located in a first plane and the at least the third plate being located in a second plane separated from the first plane, the first and second planes being at least substantially parallel;wherein first capacitance and second capacitance values are determined between the at least the third plate and the first and second plates, respectively;wherein variations of liquid height within the gap causes variations in capacitance values of the first and second measurement capacitors to thereby determine the liquid level within the container. 16. A capacitive sensor assembly according to claim 15, wherein the first measurement capacitor comprises a first section extending from the below empty condition to the empty condition. 17. A capacitive sensor assembly according to claim 16, wherein the first section is approximately equal to a difference between the second and first lengths of the second and first measurement capacitors, respectively. 18. A capacitive sensor assembly according to claim 17, wherein the first measurement capacitor comprises a second section extending from the below empty condition to the full condition. 19. A capacitive sensor assembly according to claim 18, wherein the second section is a multiple of the first section. 20. A capacitive sensor assembly according to claim 19, wherein the first length of the first measurement capacitor is a multiple of the first section.