Digital liquid level sensing apparatus

Claim 1

An apparatus for detecting a level of a liquid-based fluid, comprising: a capacitive element array including a plurality of independent input plates spaced longitudinally along an axis of measurement; a reservoir for supporting said capacitive element array thereon and a quantity of said fluid therein, said reservoir having an interior wall and an exterior wall and having a metallized surface forming an output plate which substantially conforms to the cross-sectional shape of the reservoir, the output plate being spaced apart from said input plates and having a length sufficient to span all of said input plates; a controller for sequentially applying an input signal to each one of said input plates sequentially, one at a time, to thereby electrically excite each said input plate; a current-to-voltage amplifier responsive to said output plate for generating a voltage output signal representative of the current coupled onto said output plate each time one of said input plates is electrically excited by said controller; a peak detector responsive to said current-to-voltage amplifier for generating a peak voltage signal representative of the peak magnitude of the voltage signal from said current to voltage amplifier each time one of said input plates is electrically excited by said controller; memory for storing each one of said peak voltage signals associated with the current coupled onto said output plate for each input plate excited by said controller; said controller including a comparator for comparing said peak voltage signals generated from the excitation of said input plates, one of said input plates at a time in sequential fashion against a reference value, and for determining the difference in each of said peak voltage signals from said reference value, to thereby detect a change in a dielectric of said fluid adjacent any one of said input plates relative to said reference value, to thereby detect a liquid/air interface within said fluid reservoir from which a level of said fluid can be determined; and said controller further operating to determine the percentage of each said input plate that is disposed below said liquid/air interface such that a precise level of said fluid can be determined.

Claim 2

An apparatus for detecting a level of a liquid-based fluid, comprising: a capacitive element array including a plurality of independent input plates spaced longitudinally along an axis of measurement; a reservoir for supporting said capacitive element array thereon and a quantity of said fluid therein, said reservoir having an interior wall and an exterior wall and having a metallized surface forming an output plate which substantially conforms to the cross-sectional shape of the reservoir, the output plate being spaced apart from said input plates and having a length sufficient to span all of said input plates; a controller for sequentially applying an input signal to each one of said input plates sequentially, one at a time, to thereby electrically excite each said input plate; a current-to-voltage amplifier responsive to said output plate for generating a voltage output signal representative of the current coupled onto said output plate each time one of said input plates is electrically excited by said controller; a peak detector responsive to said current-to-voltage amplifier for generating a peak voltage signal representative of the peak magnitude of the voltage signal from said current to voltage amplifier each time one of said input plates is electrically excited by said controller; memory for storing each one of said peak voltage signals associated with the current coupled onto said output plate for each input plate excited by said controller; said controller including a comparator for comparing said peak voltage signals generated from the excitation of said input plates, one of said input plates at a time in sequential fashion against a reference value, and for determining the difference in each of said peak voltage signals from said reference value, to thereby detect a change in a dielectric of said fluid adjacent any one of said input plates relative to said reference value, to thereby detect a liquid/air interface within said fluid reservoir from which a level of said fluid can be determined; and said controller further operating to determine the percentage of each said input plate that is disposed below said liquid/air interface such that a precise level of said fluid can be determined.

Claim 14

A method for detecting a level of a liquid within a liquid reservoir, the method comprising: disposing at least a portion of a probe in said reservoir, wherein said probe includes a plurality of individually excitable input plates and a common output plate, said probe being positioned relative to said reservoir such that at least a portion of one of said output plate or said at least one of said plurality of input plates are disposed in said reservoir; applying an electrical signal to each one of said input plates, sequentially, one at a time, to electrically excite each said input plate; reading an output signal generated on said output plate each time one of said input plates is electrically excited; determining whether each one of said input plates is disposed below a level of said liquid in said reservoir; extrapolating from which ones of said input plates are disposed below said level of liquid in said reservoir what an actual upper level of said liquid is within said reservoir relative to a known full level; further comprising the step of determining what percentage of each said input plate is disposed below said upper level of said liquid; and from said percentage of each said input plate which is determined to be below said upper level of said liquid, further extrapolating a precise level of said liquid within said liquid reservoir.

Claim 15

A method for detecting a level of a liquid within a liquid reservoir, the method comprising: disposing at least a portion of a probe in said reservoir, wherein said probe includes a plurality of individually excitable input plates and a common output plate, said probe being positioned relative to said reservoir such that at least a portion of one of said output plate or said at least one of said plurality of input plates are disposed in said reservoir; applying an electrical signal to each one of said input plates, sequentially, one at a time, to electrically excite each said input plate; reading an output signal generated on said output plate each time one of said input plates is electrically excited; determining whether each one of said input plates is disposed below a level of said liquid in said reservoir; extrapolating from which ones of said input plates are disposed below said level of liquid in said reservoir what an actual upper level of said liquid is within said reservoir relative to a known full level; further comprising the step of determining what percentage of each said input plate is disposed below said upper level of said liquid; and from said percentage of each said input plate which is determined to be below said upper level of said liquid, further extrapolating a precise level of said liquid within said liquid reservoir.