Fluid level sensor having capacitive sensor
First Claim
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1. A fluid level detector for detecting the level of a liquid contained within a receptacle having an electrically conductive portion, comprising:
- a probe mounted in said receptacle and electrically insulated from said receptacle, said probe acting as a first plate of a capacitor and being cooperative with said electrically conductive portion of said receptacle acting as a second plate of said capacitor, the liquid in the receptacle acting as a dielectric between said first plate and said second plate of said capacitor to produce a sensor capacitor having a capacitance which varies in magnitude in accordance with the level of liquid contained within the receptacle;
detecting circuitry coupled to said probe and responsive to a difference between a voltage decay signal derived from said sensor capacitor and a reference voltage decay signal derived from a reference capacitor to provide an output signal when a predetermined voltage difference is detected therebetween; and
indicating means coupled to said detection circuitry and responsive to said predetermined voltage difference as detected by said detection circuitry to provide an indication of the level of liquid contained within the receptacle.
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Abstract
A capacitive liquid level sensor utilizes capacitive principles to sense the level of a liquid contained within a receptacle. As a liquid rises and falls in the container, the dielectric effect of the liquid changes the effective capacitance of a sensing capacitor which is detected by electronic circuitry coupled to the sensor. One plate of the sensor capacitor is a probe disposed within a receptacle while a grounded conductive portion of the receptacle is a second plate of the capacitor. The liquid within the receptacle acts as a dielectric between the plates.
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Citations
5 Claims
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1. A fluid level detector for detecting the level of a liquid contained within a receptacle having an electrically conductive portion, comprising:
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a probe mounted in said receptacle and electrically insulated from said receptacle, said probe acting as a first plate of a capacitor and being cooperative with said electrically conductive portion of said receptacle acting as a second plate of said capacitor, the liquid in the receptacle acting as a dielectric between said first plate and said second plate of said capacitor to produce a sensor capacitor having a capacitance which varies in magnitude in accordance with the level of liquid contained within the receptacle; detecting circuitry coupled to said probe and responsive to a difference between a voltage decay signal derived from said sensor capacitor and a reference voltage decay signal derived from a reference capacitor to provide an output signal when a predetermined voltage difference is detected therebetween; and indicating means coupled to said detection circuitry and responsive to said predetermined voltage difference as detected by said detection circuitry to provide an indication of the level of liquid contained within the receptacle. - View Dependent Claims (2, 3, 4, 5)
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Specification