초록 ▼

A non-intrusive fluid level detector including a single point capacitive sensor mounted on the outside surface of a receptacle such that capacitive principles can be utilized to sense the level of a liquid contained within the receptacle. The sensor assembly is disposed in a substantially fixed posi

A non-intrusive fluid level detector including a single point capacitive sensor mounted on the outside surface of a receptacle such that capacitive principles can be utilized to sense the level of a liquid contained within the receptacle. The sensor assembly is disposed in a substantially fixed position on the exterior wall of the receptacle wherein the dielectric effect of the liquid changes the effective capacitance of the sensing capacitor as the liquid rises and falls within the receptacle. This change in effective capacitance is detected by electronic circuitry included in the detector device. In one embodiment, the fluid level detector is directly mounted to a completely non-conductive receptacle. In another embodiment, the fluid level detector is mounted to a non-conductive window which is an integral part of a receptacle fabricated out of a conductive material.

대표청구항 ▼

A non-intrusive capacitive liquid level sensor for detecting a predetermined level of liquid in a container, comprising: electrically conductive container means for storing liquid, said container means including, as an integral portion of a wall of said container means, a window of non-conductive ma

A non-intrusive capacitive liquid level sensor for detecting a predetermined level of liquid in a container, comprising: electrically conductive container means for storing liquid, said container means including, as an integral portion of a wall of said container means, a window of non-conductive material; a single capacitance plate for mounting to said window of non-conductive material, wherein said single capacitance plate is cooperative with said electrically conductive container means and the liquid therein to provide a sensor capacitor having a capacitance which varies in magnitude with respect to the amount of liquid present in said container means; detection circuit means coupled to said sensor capacitor, said detection circuit means including: an oscillator circuit coupled to said sensor capacitor for providing an oscillating voltage signal to said sensor capacitor, said sensor capacitor providing a sensor voltage decay signal as the voltage across said sensor capacitor decays over time in response to a negative transition in the oscillating voltage signal; a reference capacitor circuit coupled to said oscillator circuit for receiving said oscillating voltage signal and providing a reference voltage decay signal, as the voltage across said reference capacitor decays over time in response to a negative transition in the oscillating voltage signal; a voltage comparator circuit coupled to said sensor capacitor and to said reference capacitor circuit for receiving and comparing said reference voltage decay signal and said sensor voltage decay signal and providing an output signal when a predetermined voltage difference is detected therebetween; and indicating means coupled to said detection circuit means and responsive to said output signal to provide an indication of the presence or absence of a predetermined level of liquid in the container means.